摘要:

Subject Index 1987 Acetic Acid Ultrasonic Relaxation Studies associated with the Interactions of Acetic Acid with Some Polyvinylpyridines in Aqueous Solution, 2525 Extended X-Ray Absorption Fine Structure Study of the Reaction between Silica-supported Copper(I1) Oxide Catalysts and Acetic Acid, 2635 Acetonitrile Thermodynamic Properties of the PMMA-Acetonitrile-l,4-Dioxane System, 2289 Ace tophenones Excited-state Reactivity in a Series of Polymerization Photoinitiators based on the Acetophenone Nucleus, 2935 Acetylene An Electron Spin Resonance Study of Isomerism in a Coo Acetylene n-Complex, 3565 Acrylonitrile Acrylonitrile Polymerization from Aqueous Solution. The Role of Surfactants, 645 Acrylonitrile Polymerization from Aqueous Solution. The Role of Particle Area, 657 Activation Parameters Theoretical Analysis of Activation Parameters in Mixed Solvents Involving Various Chemical Equilibria.Reaction of Ethyl Iodide with Bromide Ion in N-Methylacetamide-Acetonitrile and N-Methylacetamide-N,N,- Dimethylacetamide Mixtures, 1089 Activity Coefficient Theoretical Analysis of Activation Parameters in Mixed Solvents Involving Various Chemical Equilibria. Reaction of Ethyl Iodide with Bromide Ion in N-Methylacetamide-Acetonitrile and N-Methylacetamide-N,N,- Dimethylacetamide Mixtures. 1089 Adenosine Selective 'H -13C and 'H-'H Nuclear Overhauser Enhancement Studies of Adenosine-Thymidine Interaction in Solution, 1731 Adsorption Electrocatalysis under Temkin Adsorption '"Xe Nuclear Magnetic Resonance Study of Conditions, 27 I Xenon adsorbed on Zeolite NaY exchanged with Alkali-metal and Alkaline-earth Cations, 45 1 Adsorption and Dissociation of Ammonia on the Hydroxylated Surface of Magnesium Oxide Powders, 477 a Molybdena-Silica Catalyst, 81 3 2.-Measurement at Low Temperatures on TiO,.957 Cross-relaxation of Hydrogen Atoms adsorbed on Dielectric Behaviour of Adsorbed Water. Part 1 Experimental Evaluation of Adsorption Behdviour of Intermediates in Anodic Oxygen Evolution at Oxidized Nickel Surfaces, 1063 The Effect of Gasification by Air (623 K) or CO, (1098 K) in the Development of Microporosity in Activated Carbons, 1081 Monolayer Adsorption of Non-spherical Molecules on Solid Surfaces. Part 1 .-Adsorption of Hard Dumb-bells on Flat Surfaces, 1405 A Study of the Adsorption Sites on Thoria by Scanning Transmission Electron Microscopyand Fourier-transform Infrared Spectroscopy. Adsorption and Desorption of Water and Methanol, 1417 on Titanium Dioxides, 159 1 Dioxide (Rutile) Surface, 1739 Adsorption and Thermal Desorption of Carbon Monoxide over Rhodium Catalysts, 1835 Adsorption and Reaction on Strained-metal Overlayers.Cu/Ru(0001), 1967 Adsorption and Dissociation of CO, on a Potassium-promoted Rh( 11 1) Surface, 201 5 Propan-2-01 Adsorption and Decomposition on Zinc Oxide promoted by Alkali Metal, 2227 Molecular Mobility of Methane adsorbed on ZSM-5 containing Co-adsorbed Benzene, and the Location of the Benzene Molecules, 2301 Adsorption, Decomposition and Surface Reactions of Methyl Chloride on Metal Films of Iron, Nickel, Palladium, Lead, Gold and Copper, 239 1 A New Pressure-programmed Volumetric Method of Measuring Adsorption at the Gas-Solid Interface, 2693 Infrared Studies on Dinitrogen and Dihydrogen adsorbed over TiO, at Low Temperatures, 2765 Wetting of Graphite (0001) by Carbon Monoxide.A Stepwise Adsorption Isotherm Study, 3355 A 'H and 13C Nuclear Magnetic Resonance Study of the Conformation of Aerosol OT in Water and Hydrocarbon Solutions, 5 17 Water Droplets of a Water-in-oil Microemulsion, 985 Characterisatior, of Aerosol OT-stabilised Oil-in- water Microemulsions using a Time-resolved Fluorescence Method, 1493 Interfacial Tension Minima in Oil-Water-Surfactant Systems. Effects of Cosurfactant in Systems containing Sodium Dodecyl Sulphate, 2347 Structural Effects on the Adsorption of Alcohols Adsorption of Organic Molecules on a Titanium The Effect of Hydrogen Sulphide on the Aerosol OT The Kinetics of Solubilisate Exchange between11 SUBJECT INDEX Aggregation Kinetic and Equilibrium Studies associated with the Aggregation of Non-ionic Surfactants in Non-polar Solvents, 2735 Alcohols Photocatalytic Dehydrogenation of Liquid Alcohols by Platinized Anatase, 163 1 Structural Effects on the Adsorption of Alcohols on Titanium Dioxides, 159 I Aldehydes The Hydration of Aliphatic Aldehydes in Aqueous Micellar Solutions, 2847 Alkali Metals Chemical and Electrostatic Interactions between Alkali Metals and Carbon Monoxide on Metal Single-crystal Surfaces, 200 1 Propan-2-01 Adsorption and Decomposition on Zinc Oxide promoted by Alkali Metal, 2227 Alkanes Primary Processes of Stabilizer Action in Radiation-induced Alkane Oxidation, 2365 Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia, 3069 Microcalorimetric Measurement of the Enthalpies of Transfer of a Series of ortho- and pura- Alkoxyphenols from Water to Octan-1-01 and from Isotonic Solution to Escherichiu coli Cells, 2705 Alkenes Alkox yphenols Alkylammonium Salts Pairwise Gibbs Function Cospherexosphere Group Interaction Parameters for Alkylammonium Salts in Aqueous Solutions at 298 K; Solubilities of Hydrocarbons in Aqueous Salt Solutions, 3039 Alkylperoxyl Radicals Reactions of Alkylperoxyl Radicals in Solution.Part 1.-A Kinetic Study of Self-reactions of 2- Propylperoxyl Radicals between 135 and 300 K, 242 1 Part 2.-A Kinetic and Product Study of Self- reactions of 2-Propylperoxyl Radicals between 253 and 323 K, 2433 Reactions of Alkylperoxyl Radicals in Solution.Alloys Catalysis by Amorphous Metal Alloys. Part 6.-Factors controlling the Activity of Skeletal Nickel Catalysts prepared from Amorphous and Crystalline Ni-Zr Powder Alloys, 2883 Catalysis by Amorphous Metal Alloys. Part 7.-Formation of Fine Fe Particles on the Surface of an Alloy in the Precrystallisation State prepared from an Amorphous Fe,,Zr,, Powder Alloy, 2895 Aluminium Kinetics of N,O Decomposition on the Surface of y-Al,O, doped with Sodium Ions, 627 Physicochemical Characterization of ZnO/Al,O, and ZnO-MoO,/Al,O, Catalysts, 665 Influence of Lithium on Reduction, Dispersion and Hydrogenation Activity of Nickel on Alumina Catalysts, 733 Adsorption of Thiophene and Model Hydrocarbons on MoO,/y-Al,O, Catalysts studied by Gas-Solid Chromatography, 1179 Photogeneration of Hydrogen from Water over an Alumina-supported ZnS-CdS Catalyst, I395 Adsorption of Benzene on Acidified Alumina, 1469 The Effects of Titania and Alumina Overlayers on the Hydrogenation of CO over Rhodium, 206 1 Hydrodesulphurisation Catalysts supported on Carbon and Alumina, 2145 Ruthenium supported on y-Alumina, 2271 An Electron Spin Resonance Investigation, 3619 Aluminium Distribution in the Bulk and on the Surface of Y Zeolites Dealuminated with SiCl, Vapour.Influence of Conditions of Dealumination, 5 1 1 [A1,,O,,H,,I7+, 1725 in Zeolitic Frameworks, 268 1 Tetrahydrofuran Solutions of AIC1,-LiAlH, using Microelectrodes.Part 1 .--1 : 1 AlCl, -LiAlH,, 2787 Tetrahydrofuran Solutions of AlCl, -LiAlH, using Microelectrodes. Part 2.-The Influence of Solution Composition, 2795 The Role of Co in Sulphidised C e M o Electron Spin Resonance Investigations of Interaction of Carbon Monoxide with Ru/yAl,O,. The Molar Volume of a Large Polymeric Cation Determination of the Distribution of Aluminium The Study of Aluminium Deposition from The Study of Aluminium Deposition from Amides Radical Production evidenced by Dimer Analysis in y-Irradiated Amides in Aqueous Solutions and in the Solid State, 125 Amines Electrostatic Interactions between Organic Ions. Part 2.-Phosphates with Amines, 1885 Aminocoumanns Solvent and Substituent Effects on Intramolecular Charge Transfer of Selected Derivatives of 4- Trifluoromethyl-7-aminocoumarin, 2533 Ammonia Adsorption and Dissociation of Ammonia on the Hydroxylated Surface of Magnesium Oxide Powders, 477 Chemisorption and Ammonia Synthesis on Alumina-supported Hexagonal Tungsten Bronze, K, WO,, 2175 Promotion of Nitrogen and Hydrogen Ammonium Salts Pulse Radiolysis Study of Salt Effects on Reactions of Aromatic Radical Cations with Cl-.Rate Constants in the Absence and Presence of Quaternary Ammonium Salts, 1795 Micelle Formation of Ionic Amphiphiles. Amphiphile Thermochemical Test of a Thermodynamic Model, 3331 Anatase Photocatalytic Dehydrogenation of Liquid Alcohols by Platinized Anatase, 163 1... SUBJECT INDEX 111 Anthralin Formation of Superoxide during the Auto- oxidation of Anthralin (1,8-Dihydroxy-9- anthrone), 85 Anthraquinol Electron Spin Resonance, ENDOR and TRIPLE Resonance of some 9,lO-Anthraquinone and 9,lO-Anthraquinol Radicals in Solution, 5 1 Anthraquinone Electron Spin Resonance, ENDOR and TRIPLE Resonance of some 9,IO-Anthraquinone and 9,IO-Anthraquinol Radicals in Solution, 5 1 Generation of Radicals from Antioxidant- type Molecules by Polyunsaturated Lipids, 141 Antioxidants Antitumour Agents Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution, 151 Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution.Part 2.-Rifamycins, 3675 Aprotic Solvents Basicity of Water in Dipolar Aprotic Solvents using the 1,4,8,1l-Tetramethyl-1,4,8,1 I-tetra- azacyclotetradecaneNickel(I1) Cation as a Probe of Electron-pair Acceptance, 1641 Aqueous Solutions Measurements of Tracer Diffusion Coefficients of Lithium Ions, Chloride Ions and Water in Aqueous Lithium Chloride Solutions, 1779 A Neutron Scattering Study, 687 Group Interaction Parameters for Alkylammonium Salts in Aqueous Solutions at 298 K; Solubilities of Hydrocarbons in Aqueous Salt Solutions, 3039 Absence of Fast H+-ion Motion in Aqueous HCl.Pairwise Gibbs Function Cosphere-Cosphere Aromatic Radicals Pulse Radiolysis Study of Salt Effects on Reactions of Aromatic Radical Cations with C1-. Rate Constants in the Absence and Presence of Quaternary Ammonium Salts, 1795 Aromatization Transformation of But- 1-ene into Aromatic Hydrocarbons over ZSM-5 Zeolites, 291 3 An Electron Spin Resonance Study of Single Ascorbic Acid Crystals of X-irradiated L-Ascorbic Acid at Room Temperature.Experimental Results and Semiempirical Calculations, 893 Radical Pairs in Single Crystals of X-Irradiated L-Ascorbic Acid at 77 K, 1869 An Electron Spin Resonance Study of Triplet Association Constants Electrostatic Interactions between Organic Ions. Part 2.-Phosphates with Amines, 1885 Primary Processes of Stabilizer Action in Auto-oxidation Radiation-induced Alkane Oxidation, 2365 Belousov-Zhabotinsky System Influence of Mixed Cerium(1v) Sulphate and Ferroin Catalysts on the Oscillatory Redox Reaction between Malonic Acid and Bromate, 267 Benzene Properties of Capillary-condensed Benzene, 1203 Adsorption of Benzene on Acidified Alumina, Molecular Mobility of Methane adsorbed on 1469 ZSM-5 containing Co-adsorbed Benzene, and the Location of the Benzene Molecules, 2301 Non-ideal Behaviour of Benzene Solutions of Tri- n-octylammonium Bromide and Cyclohexanol, 231 I Assessment of Some Vapour-pressure Equations, 2709 2.-Saturated Vapour Pressures from 279 to 300 K, 2719 Neutron Spectroscopic Study of Polycrystalline Benzene and of Benzene adsorbed in Na-Y Zeolite, 3 199 Benzene Cations, 759 The Vapour Pressure of Benzene.Part 1 .--An The Vapour Pressure of Benzene. Part INDO and CND0/2 Calculations for Substituted Benzonitrile Single-ion Free Energies for Transfers to Benzonitrile derived from Solubility and Complexing Data, 1569 Benzoquinones Electron Spin Resonance Spectroscopy as an Analytical Tool, 107 Binary Mixtures Refractive Index and Excess Volume for Binary Liquid Mixtures.Part 1 .-Analyses of New and Old Data for Binary Mixtures, 2449 Benzene, Toluene, p-Xylene, Quinoline and Cyclohexane. Part 3.-Dielectric Properties and Refractive Indices at 308.15 K, 3167 Binary Systems of 1,2-DichIoroethane with Biomolecular Dynamics Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution, 15 1 Bip yridine A Study of Proton Transfer by 2,2’-Bipyridine from Water to Nitrobenzene using Chronopotentiometry with Cyclic Linear Current-scanning and Cyclic Voltammetry, 2993 2,2’-Bipyrimidine One-electron Reduction of 2,2’-Bipyrimidine in Aqueous Solution, 341 5 Bismuth CH Bond Activation and Radical-Surface Reactions for Propylene and Methane over a-Bi,O,, 463 Bithionol An Electron Spin Resonance Study of the Radicals formed on Ultraviolet Irradiation of the Photoallergens Fentichlor and Bithionol, 135 Boron A Polarimetric, Circular Dichroism and “B Nuclear Magnetic Resonance Study of the Reaction of the Tetrahydroxyborate Ion with Two Chiral 1,3-Diols, 771iV SUBJECT INDEX Boron (cont.) Origin of Boron Mobility over Boron-impregnated ZSM-5.A Combined High-resolution-Solid- state "B Nuclear Magnetic Resonance/Infrared Spectral Investigation, 1751 1 -Bromo-2-methylpropane Study of the Conformational Equilibria between Rotational Isomers using Ultrasonic Spectroscopy. Part 1 .-1 -Chloro-2- methylpropane and I-Bromo-2-methylpropane, 527 But-l-ene Transformation of But- 1-ene into Aromatic Hydrocarbons over ZSM-5 Zeolites, 29 13 Catalysis by Amorphous Metal Alloys.Part 7.-Formation of Fine Fe Particles on the Surface of an Alloy in the Precrystallisation State prepared from an Amorphous Fe,,Zr,, Powder Alloy, 2895 Buta-l,3-&ne Butane Effects of the Oxidation State of Cerium on the Reactivity and Sulphur Resistance of Nio/ Zeolite, Nio/Silica and Nio/CeO, Catalysts in Butane Hydrogenolysis, 1 137 Rotational Isomers of the n-Butane Radical Cation with Partially Deuterated Methyl Groups in Some Halogenated Matrices, 18 15 Hydrogenation of Conjugated Dienes and Electron Spin Resonance Characterization of Butem lsomerization of Butenes on CdO, Co,O, and Crz03, 1213 Butyl Acrylate Emulsion Polymerization of Butyl Acrylate.Kinetics of Particle Growth, 1449 Butyl Alcohol Standard Gibbs Free Energies of Transfer of NaCl and KCI from Water to Mixtures of the Four Isomers of Butyl Alcohol with Water. The Use of Ion-selective Electrodes to Study the Thermodynamics of Solutions, 635 Dichlorobis( 1,2-diaminoethane)cobalt(111) Ion in Water and in Water-t-Butyl Alcohol Mixtures, 1119 Cadmium Kinetics of the Solvolysis of the cis- Medium Effect on the Electrochemical Behaviour of the Cd"/Cd (Hg) System in Propane-1,2- diol-Water Mixtures, 28 13 lsomerization of Butenes on CdO, Co30, and Cr,O,, 1213 Hydrogen Adsorption and CO-H, Interaction at MgO and CaO Surfaces, 1237 studied by Pulse Radiolysis, 1193 Semiconductor-Electrolyte Interfaces in CdS Suspensions, 2647 Hjrdrogenation of Conjugated Dienes and Ultraviolet-Visible Reflectance Studies of Electron-transfer Reactions on CdSe Colloids as Methyl Orange as a Probe of the Caesium Alkali Metal, Chlorine and other Promoters in the Silver-catalysed Selective Oxidation of Ethylene, 2035 Calcination Control of Ni Metal Particle Size in Ni/SiO, Catalysts by Calcination and Reduction Temperatures, 3 189 Calcium Effusion Mass Spectrometric Determination of Thermodynamic Properties of the Gaseous Mono- and Di-hydroxides of Calcium and KCaO(g), 3229 Effect of Diphosphonates on the Precipitation of Calcium Carbonate in Aqueous Solutions, 1477 Surface Reactivity and Spectroscopy of Alkaline- earth Oxide Powders.Part 3.--'H/,H and laO/'sO Exchange on Specpure CaO, 2973 Free Energies, Enthalpies and Entropies of the Monothiocyanate Complex Formation of Trivalent Metals in Dimethyl Sulphoxide Solutions, 1253 Microcalorimetric Measurement of the Enthalpies of Transfer of a Series of ortho- and para- Alkoxyphenols from Water to Octan- 1-01 and from Isotonic Solution to Escherichia cofi Cells, 2705 Ternary Systems.Part 4.--The Influence of Solvation on Enthalpy of Complex Formation in Phenol-Tetrahydrofuran and 2,6- Dimet hy lphenol-tetrahydro furan S y s terns, 308 3 Micelle Formation of Ionic Amphiphiles. Thermochemical Test of a Thermodynamic Model, 3331 Capillary Condensation Capillary Gas Chromatography Calorimetry Calorimetric Investigations of Association in Properties of Capillary-condensed Benzene, 1203 Radical Production evidenced by Dimer Analysis in ?-Irradiated Amides in Aqueous Solutions and in the Solid State, 125 Carbocations Formation of Carbocations from C, Compounds in Zeolites of Different Acidities, 1109 Carbohydrates Selective Formation and Conformational Analysis of Carbohydrate-derived Radicals, 95 Carbon The Effect of Gasification by Air (623 K) or CO, (1098 K) in the Development of Microporosity in Activated Carbons, 1081 Hydrodesulphurisation Catalysts supported on Carbon and Alumina, 2145 naphthoquinones immobilized at Carbon Electrodes, 1823 The Role of Co in Sulphidised Co-Mo Oxygen Reduction with Hydroxy- 1,4- Carbon Dioxide Exchange of Oxygen Isotopes between Carbon Dioxide and Ion-exchanged Zeolites A, 41 1 Adsorption and Dissociation of CO, on a Potassium-promoted Rh( 11 1) Surface, 2015 Radiotracer Studies of Chemisorption on Copper- based Catalysts.Part 1 .-The Adsorption of Carbon Monoxide and Carbon Dioxide on Copper/Zinc Oxide/Alumina and Related Catalysts, 3399SUBJECT INDEX V Carbon Monoxide Dynamic Kinetics of CO Oxidation over Ultraviolet-Visible Reflectance Studies of Magnesium Oxide, 721 Hydrogen Adsorption and CO-H, Interaction at MgO and CaO Surfaces, 1237 Electrical and Catalytic Properties of some Oxides with the Fluoriteor Pyrochlore Structure. CO Oxidation on some Compounds derived from Gd,Zr,O,, 1485 Adsorption and Thermal Desorption of Carbon Monoxide over Rhodium Catalysts, 1835 Coordination of Carbon Monoxide to Transition- metal Surfaces, 1915 Catalytic Implications of Local Electronic Interactions between Carbon Monoxide and Coadsorbed Promoters on Nickel Surfaces, 1945 Overlayers.Cu/Ru(0001), 1967 Alkali Metals and Carbon Monoxide on Metal Single-crystal Surfaces, 200 1 The Effects of Titania and Alumina Overlayers on the Hydrogenation of CO over Rhodium, 2061 Chemisorption and Disproportionation of Carbon Monoxide on Palladium/ Silica Catalysts of differing Percentage Metal Exposed, 2757 Cobalt-Manganese Oxide Catalyst. A 13C Isotopic Study, 2963 Wetting of Graphite (OOO1) by Carbon Monoxide. A Stepwise Adsorption Isotherm Study, 3355 Radiotracer Studies of Chemisorption on Copper- based Catalysts. Part 1 .--The .4dsorption of Carbon Monoxide and Carbon Dioxide on Copper/Zinc Oxide/Alumina and Related Catalysts, 3399 Interaction of Carbon Monoxide with Ru/yAl,O,. An Electron Spin Resonance Investigation, 3619 The Etrect of Hydrogen Sulphide on the Adsorption and Reaction on Strained-metal Chemical and Electrostatic Interactions between Formation of Hydrocarbons from CO+H, using a Carbon Tetrachloride Spin-trapping Study of the Radiolysis of CCl,, Infrared Study of the Desorption of 219 Polycondensed Aromatic Compounds by Non- ionic Surfactants at the Silica-Carbon Tetrachloride Interface, 3295 Catalysis CH Bond Activation and Radical-Surface Reactions for Propylene and Methane over a-Bi,O,, 463 Aluminium Distribution in the Bulk and on the Surface of Y Zeolites Dealuminated with SiCI, Vapour.Influence of Conditions of Dealumination, 5 1 1 Catalytic Properties of Synthetic Faujasites Modified with Fluoride Anions, 535 Hydrocarbon Formation from Methylating Agents over the Zeolite Catalyst ZSM-5. Comments on the Mechanism of Carbon-Carbon Bond and Methane Formation, 57 I Structures of Vanadium Oxide on Various Supports, 675 Fourier-transform Infrared Investigation of Dynamic Kinetics of CO Oxidation over Magnesium Oxide, 721 Cross-relaxation of Hydrogen Atoms adsorbed on a Molybdena-Silica Catalyst, 8 13 Influence of Metal-Support Interactions on the Hydrogenolysis of Methylcyclopentane over Supported Rh Catalysts, 9 13 The Effect of Gasification by Air (623 K) or CO, (1098 K) in the Development of Microporosity in Activated Carbons, 1081 uptake of Oxygen in Colloidal Suspensions of a- Fe,O,, 1101 Hydrocarbons on MoO,/y-Al,O, Catalysts studied by Gas-Solid Chromatography, 1 179 Isomerization of Butenes on CdO, Co,O, and Cr203, 1213 supported Catalyst derived from Copper(I1) Acetate, 1227 Hydrogen Adsorption and CO-H, Interaction at MgO and CaO Surfaces, 1237 Reaction of Neopentane with Hydrogen over Pd, Pt, Ir and Rh, 1293 Nature of Oxide-supported Copper(I1) Ions and Copper derived from Copper(1r) Chloride, 1347 The Role of Electron Transfer Processes in Determining Desorption Kinetics, 1363 Aspects of Temperature-programmed Analysis of some Gas-Solid Reactions.Part 2.-Hydrogen Temperature-programmed Desorption from Silica-supported Platinum, I369 Infrared Spectroscopic Study of Catalytic Activity of Rh/TiO, for the CO+H, Reaction. 1427 Adsorption of Benzene on Acidified Alumina, 1469 Electrical and Catalytic Properties of some Oxides with the Fluoriteor Pyrochlore Structure.CO Oxidation on some Compounds derived from Gd,Zr,O,, 1485 Oxygen Evolution by Water Oxidation with Polynuclear Ruthenium Complexes, 1539 The Nature of Supported-molybdena Catalysts. Evidence from a Raman and X-Ray Diffraction Investigation of Pyridine Adsorption, 160 1 Isothermal Titration of Supported Platinum. Part 1 .--Co-O, Titration, 165 1 Isothermal Titration of Supported Platinum. Part 2.-Alkene Titration using Cyclohexene, 1667 Hydrogenation of CO, over Co/Cu/K Catalysts, 171 1 Catalytic Activity and Structure of Mo Oxide Highly Dispersed on ZrO, for Oxidation Reactions, 176 1 Conversion, I77 1 Homologation Reaction on Molybdena-Silica Catalysts, 1859 Promotion in Heterogeneous Catalysis: Retrospect and Prospect, 1893 Light-induced Hydrogen Formation and Photo- Adsorption of Thiophene and Model Hydrogenation of Conjugated Dienes and Structure of the Catalytic Site on the Silica- Ultraviolet-Visible Reflectance Studies of Comments on the Mechanism of MTG/HZSM-5 Reactive Intermediates for the Ethenevi SUBJECT INDEX Catalysis (cont.) Adsorption and Reaction on Strained-metal Overlayers.Cu/Ru(0001), 1967 Alkali Metal, Chlorine and other Promoters in the Silver-catalysed Selective Oxidation of Ethylene, 2035 The Effects of Titania and Alumina Overlayers on the Hydrogenation of CO over Rhodium, 2061 Comparison of Hydrogenation and Hydrogenolysis on Unsupported and Silica- supported Rh-V,O, and Pt-V,O,, 2091 Promotion of Platinum-based Catalysts for Methanol Synthesis from Syngas, 21 I3 Mechanism of Deuterium Addition and Exchange with Propene over Ni/SiO, and Pt/SiO, Catalysts at Low Temperatures, 2475 Kinetics of Inhibition Reactions in the Hydrogenolysis of C,H, on a Nickel Wire Catalyst, 2825 Catalysis by Amorphous Metal Alloys. Part 6.-Factors controlling the Activity of Skeletal Nickel Catalysts prepared from Amorphous and Crystalline Ni-Zr Powder Alloys, 2883 Catalysis by Amorphous Metal Alloys.Part 7.-Formation of Fine Fe Particles on the Surface of an Alloy in the Precrystallisation State prepared from an Amorphous Fe,,Zr,, Powder Alloy, 2895 Surface Reactivity and Spectroscopy of Alkaline- earth Oxide Powders. Part 3.--'H/'H and l80/l6O Exchange on Specpure CaO, 2973 Activity and Selectivity in Toluene Oxidation on Well Characterized Vanadium Oxide Catalysts, 3303 Radiotracer Studies of Chemisorption on Copper- based Catalysts. Part 1 .-The Adsorption of Carbon Monoxide and Carbon Dioxide on Copper/Zinc Oxide/Alumina and Related Catalysts, 3399 An In Situ Mossbauer Spectroscopic Investigation of Titania-supported Iron-Ruthenium Catalysts, 2573 Extended X-Ray Absorption Fine Structure Study of the Reaction between Silica-supported Copper(I1) Oxide Catalysts and Acetic Acid, 2635 on the Structure and Properties of Molybdena-Silica Catalysts, 2835 Kinetic Modelling of Multiple-site Activity and the Study of the Influence of the Impregnation Acidity Cation Exchange Membranes Electrochemical Properties of Cation Exchange Membranes, 284 1 Cation Migration Linewidth Alternation, as a Result of Intramolecular Cation Migration, in the Electron Spin Resonance Spectrum of the 1,4- Naphthoquinone Radical Anion, 167 Cerium Effects of the Oxidation State of Cerium on the Reactivity and Sulphur Resistance of Nio/ Zeolite, Nio/Silica and Nio/CeO, Catalysts in Butane Hydrogenolysis, 1 137 Ethanol Promotion by the Addition of Cerium to Rhodium-Silica Catalysts, 21 19 Corrosion of Ruthenium Dioxide Hydrate by Ce'" Ions and other Oxidants, 2317 Chalcogenides Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalcogenides, 3527 Charcoal Heterogeneous Decomposition of Trichlorofluoromethane on Carbonaceous Surfaces, 3055 Charge Transfer Site-transfer Conductivity in Solid Iron Hexacyanoferrates by Dielectric Relaxometry, Voltammetry and Spectroscopy.Prussian Blue, Congeners and Mixtures, 23 1 Solvent and Substituent Effects on Intramolecular Charge Transfer of Selected Derivatives of 4- Trifluoromethyl-7-aminocoumarin, 2533 Spectromagnetic Evidence for Spatial Correlation of Copper Centres in Phosphate Glasses and its Effect on the Charge-transport Processes, 3587 Chemical Equilibria Chemical Equilibria and Kinetics at Constant Pressure and at Constant Volume, 2901 Chemisorption Chemisorption and Catalysis by Metal Clusters. Hydrogenation of Carbon Monoxide and Carbon Dioxide catalysed by Supported Ruthenium Clusters derived from Ru,(CO),, and from H,Ru,(CO),,, 905 1 .-Measurement at Room Temperature on TiO,, 943 Gaseous Additives. The Role of a Surface Oxygen Transient, 2047 Chemisorption and Ammonia Synthesis on Alumina-supported Hexagonal Tungsten Bronze, K, WO,, 2175 Monoxide on Palladium/Silica Catalysts of differing Percentage Metal Exposed, 2757 Radiotracer Studies of Chemisorption on Copper- based Catalysts.Part 1 .-The Adsorption of Carbon Monoxide and Carbon Dioxide on Copper/Zinc Oxide/Alumina and Related Catalysts, 3399 Dielectric Behaviour of Adsorbed Water. Part The Promotion of Surface-catalysed Reactions by Promotion of Nitrogen and Hydrogen Chemisorption and Disproportionation of Carbon Chlorine Alkali Metal, Chlorine and other Promoters in the Silver-catalysed Selective Oxidation of Ethylene, 2035 l-Chlorohexane Thermodynamics of Mixtures with a Hexane Isomer. Excess Volumes of 1-Chlorohexane with a Hexane Isomer at 298.15 K, 819 Chlorohydrocarbons Study of the Conformational Equilibria between Rotational Isomers using Ultrasonic Spectroscopy.Part 1 .-1 -Chloro-2- methylpropane and l-Bromo-2-methylpropane, 527 Reactions of Aromatic Radical Cations with C1-. Rate Constants in the Absence and Presence of Quaternary Ammonium Salts, 1795 Pulse Radiolysis Study of Salt Effects onSUBJECT INDEX vii Chromium Kinetics of Metal Oxide Dissolution. Oxidative Dissolution of Chromium from Mixed Nickel-Iron-Chromium Oxides by Permanganate, 371 The Promoting Role of Cr and K in Catalysts from High-pressure and High-temperature Methanol and Higher-alcohol Synthesis, 221 3 Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalcogenides, 3527 Electron Spin Resonance Spectra of CpCr(CO), and CpCr(CO),P(C,H,), in Single Crystals of their Mn Analogues, 3535 An Electron Spin Resonance Study of Rutile and Anatase Titanium Dioxide Polycrystalline Powders treated with Transition-metal Ions, 3541 Isomerization of Butenes on CdO, Co,O, and Cr,O,, 1213 Chronopotentiometr y Hydrogenation of Conjugated Dienes and A Study of Proton Transfer by 2,2'-Bipyridine from Water to Nitrobenzene using Chronopotentiometry with Cyclic Linear Current-scanning and Cyclic Voltammetry, 2993 Circular Dichroism A Polarimetric, Circular Dichroism and "B Nuclear Magnetic Resonance Study of the Reaction of the Tetrahydroxyborate Ion with Two Chiral 1,3-Diols, 77 I Clays Metachromasy in Clay Minerals.Sorption of Pyronin Y by Montmorillonite and Laponite, 1685 Cluster Compounds Inorganic Cluster Compounds as Models for the Structure of Active Sites in Promoted Hydrodesulphurisation Catalysts, 21 57 Electrostatic Interactions and their Role in Coadsorption Coadsorption Phenomena, 1935 Cobalt The Use of Hydride-forming Rare-earthxobalt Intermetallic Compounds in the Dehydrogenation of Propan-2-01, 743 Iron(I1) Cobalt Ferrites.Preparation and Interfacial Behaviour, 11 59 Hydrogenation of CO, over Co/Cu/K Catalysts, 171 1 The Role of Co in Sulphidised C*Mo Hydrodesulphurisation Catalysts supported on Carbon and Alumina, 2145 An Electron Spin Resonance Study of Isomerism in a Coo Acetylene n-Complex, 3565 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(I1) ",I-Macrocyclic Complexes. A Means of Breaking the Co-C Bond in B12 Co-enzyme, 3663 Isomerization of Butenes on CdO, Co,O, and Cr,O,, 1213 Dehydrogenation of Ethane and Small Alkanes with Nitrous Oxide over Cobalt-doped Magnesium Oxide, 3 139 Hydrogenation of Conjugated Dienes and Kinetics and Mechanism of Oxidative Ionization Equilibria in Solutions of Cobalt(i1) Kinetics of the Solvolysis of the cis- Thiocyanate in N,N-Dimethylformamide, 2261 Dichlorobis( 1,2-diaminoethane)cobalt(111) Ion in Water and in Water-t-Butyl Alcohol Mixtures, 1119 Colloids Corrosion Processes in Quantized Semiconductor Colloids studied by Pulse Radiolysis, 1127 Photochemical Formation of Colloidal Metals, 1559 Concentration Dependence of Spin Friction Coefficients in Suspensions of Parallel Cylinders and Spheres, 547 The Consolidation of Concentrated Suspensions. Part 1 .-The Theory of Sedimentation, 873 Light-induced Hydrogen Formation and Photo- uptake of Oxygen in Colloidal Suspensions of a- Fe,O,, 1101 studied by Pulse Radiolysis, 1193 Comparison of Radiation-generated and Chemically-generated RuO, .2H,O and MnO, Colloids, 300 1 Electron-transfer Reactions on CdSe Colloids as Redox Reactions with Colloidal Metal Oxides.Complex Formation Free Energies, Enthalpies and Entropies of the Monothiocyanate Complex Formation of Trivalent Metals in Dimethyl Sulphoxide Solutions, 1253 Sodium Ion Exchange on the 1,4,7,10,13,16- Hexaoxaoctadecanesodium(1) Cation ("a. 18C6]+) in Several Solvents. A Sodium-23 Nuclear Magnetic Resonance Study, 2459 Ternary Systems. Part 4.-The Influence of Solvation on Enthalpy of Complex Formation in Phenol-Tetrahydrofuran and 2,6- Dimethylphenol-Tetrahydrofuran Systems, 3083 Complexation and Transfer Free Energies of Calorimetric Investigations of Association in Metal-ion Dibenzocryptates, 2663 Compressibility Volume and Compressibility Changes in Mixed- salt Solutions at 25 "C, 2467 Concentration Gradient Origin of Idealized Static Thermodynamic Forces inducing Solid Particle Motion, Orientation and Related Effects in a Solute Concentration Gradient, 1269 Conductance Dynamic Properties and Structure of Salt-free Tin Dioxide Gas Sensors.Part 1.-Aspects of the Polystyrene Sulphonate Solutions, 801 Surface Chemistry revealed by Electrical Conductance Variations, 1323 Effect of 1,4-Dioxane on the Conductance and Ion-pairing of Hydrogen Chloride in Wet and Dry Methanol Mixtures at 25 "C, 1437 Conductivity Electron-transfer Rates by Dielectric Relaxometry and the Direct-current Conductivities of Solid Homonuclear and Heteronuclear Mixed-valence Metal Cyanometallates and of the Methylene Blue-Iron Dithiolate Adduct, 245...Vlll SUBJECT INDEX Conductivity (cont.) Absence of Fast H+-ion Motion in Aqueous HCl. Electrochemical Properties of Cation Exchange The Conductivity of Dilute Solutions of Mixed A Neutron Scattering Study, 687 Membranes, 2841 Electrolytes. Part 1 .-The System NaCI-BaCl,-H,O at 298.2 K, 3027 Differential Thermal Analysis, X-Ray Powder Diffraction and Electrical Conductivity Studies on the Motion of Cations, including Self- diffusion in Crystals of Propylammonium Chloride and Bromide as well as their N- Deuterated Analogues, 3207 Transport Phenomena in Concentrated Aqueous Solutions of Sodium-Caesium Polystyrene Sulphonates, 3259 Polymer Electrolytes, 3345 Hydrogen- 1 Nuclear Magnetic Resonance, The Mechanism of Conductivity of Liquid Configurational Theory Towards a Complete Configurational Theory of Non-equilibrium Polymer Adsorption, 25 15 Study of the Conformational Equilibria between Conformation Rotational Isomers using Ultrasonic Spectroscopy.Part I .-1 -Chloro-2- methylpropane and l-Bromo-2-methylpropane, 527 Selective Formation and Conformational Analysis of Carbohydrate-derived Radicals, 95 Copper Nature of Oxide-supported Copper(1r) Ions and Comer derived from Copper(I1) Chloride, 1347 Hydrogenation of CO, over Co/Cu/K Catalysts, 171 I Adsorption and Reaction on Strained-metal Overlayers.Cu/Ru(0001), 1967 A Comparison of the Effects of Cu and Au on the Surface Reactivity of Ru(0001), 1975 Promotion of Methanol Synthesis and the Water- gas Shift Reactions by Adsorbed Oxygen on Supported Copper Catalysts, 2193 Interpretation of Electron Spin-echo Modulation for Copper(I1) Complexes in Crystalline Powders, 3505 Binding of Paramagnetic Ions in Ionomers. CU" and Ti3+ in Nafion Membranes, 3575 Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution, 15 1 Spectromagnetic Evidence for Spatial Correlation of Copper Centres in Phosphate Glasses and its Effect on the Charge-transport Processes, 3587 Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution.Part 2.-Rifamycins, 3675 Nature of the Complexes formed between Copper(n) and Glycylhistidine, 3683 A Vibronic Coupling Approach for the An Electron Spin Resonance Investigation of the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins, 3693 Structure of the Catalytic Site on the Silica- supported Catalyst derived from Copper(r1) Acetate, 1227 of the Reaction between Silica-supported Copper(r1) Oxide Catalysts and Acetic Acid, 2635 Hydrazine Reduction of Transition-metal Oxides, 327 1 Corrosion Extended X-Ray Absorption Fine Structure Study Corrosion Processes in Quantized Semiconductor Colloids studied by Pulse Radiolysis, 1127 Corrosion of Ruthenium Dioxide Hydrate by CeIV Ions and other Oxidants, 23 I7 Thermally Activated Ruthenium Dioxide Hydrate.A Reproducible, Stable Oxygen Catalyst, 233 1 Crown Ethers Sodium Ion Exchange on the 1,4,7,10,13,16- Hexaoxaoctadecanesodium( I) Cation ("a. 18C6]+) in Several Solvents. A Sodium-23 Nuclear Magnetic Resonance Study, 2459 Cyclic Voltammetry Experimental Evaluation of Adsorption Behaviour of Intermediates in Anodic Oxygen Evolution at Oxidized Nickel Surfaces, 1063 Electrogenerated R,N(Hg), Films, 1169 Determination of Stability Constants from Linear- scan or Cyclic-voltammetric Data using a Non- linear Least-squares Method, 17 19 Oxygen Reduction with Hydroxy- 1,4- naphthoquinones immobilized at Carbon Electrodes, 1823 Medium Effect on the Electrochemical Behaviour of the Cd"/Cd (Hg) System in Propane- 1,2- diol-Water Mixtures, 28 13 A Study of Proton Transfer by 2,2'-Bipyridine from Water to Nitrobenzene using Chronopotentiometry with Cyclic Linear Current-scanning and Cyclic Voltammetry, 2993 C yclodextrin The Inclusion of Tropaeolin OOO No.2 by Permethylated P-Cyclodextrin. A Kinetic and Equilibrium Study, 275 1 Cyclodextrins. A "F Nuclear Magnetic Resonance and Spectrophotometric Study, 2697 Cyclodextrin. A Kinetic and Equilibrium Study, 3237 C yclohexanol The Inclusion of Diflunisal by a- and P- The Inclusion of Pyronine Y by P- and y- Non-ideal Behaviour of Benzene Solutions of Tri- n-octylammonium Bromide and Cyclohexanol, 231 1 Cyclohexyl- 1 4 Radical Two-dimensional Transient Electron Spin Resonance Spectroscopy, 29 Cyclopentadienyl Radicals The Electron Spin Resonance Spectra of CpCr(CO), and CpCr(CO),P(C,H,), in Single Crystals of their Mn Analogues, 3535SUBJECT INDEX ix Cysteine Oxovanadium(1v) Complexes of Cysteine characterized by Electron Spin Resonance Spectroscopy, 3627 Dealumination Dealumination of Sodium Y Zeolite with Hydrochloric Acid, 153 1 Decomposition Adsorption, Decomposition and Surface Reactions of Methyl Chloride on Metal Films of Iron, Nickel, Palladium, Lead, Gold and Copper, 239 1 Trichlorofluoromethane on Carbonaceous Surfaces, 3055 Heterogeneous Decomposition of Dehydration Tin Oxide Surfaces.Part 17.-An Infrared and Thermogravimetric Analysis of the Thermal Dehydration of Tin(Iv) Oxide Gel, 3383 Dehydrogenation Investigation of the Mechanism of Photocatalytic Alcohol Dehydrogenation over Pt/TiO, using Poisons and Labelled Ethanol, 697 The Use of Hydride-forming Rare-earthxobalt Intermetallic Compounds in the Dehydrogenation of Propan-2-01, 743 Photocatalytic Dehydrogenation of Liquid Alcohols by Platinized Anatase, I63 1 The Role of Electron Transfer Processes in Determining Desorption Kinetics, 1363 Temperature-programmed Desorption Study of the Interactions of H,, CO and CO, with LaMnO,, 3 149 Desorption Deuteration Hydrogenation of Conjugated Dienes and Isomerization of Butenes on CdO, Co,O, and Cr203, 1213 Mechanism of Deuterium Addition and Exchange with Propene over Ni/SiO, and Pt/SiO, Catalysts at Low Temperatures, 2475 Deuterium Oxide Internal Pressures, Temperatures of Maximum Density and Related Properties of Water and Deuterium Oxide, 1783 Dialkyl Sulphoxides Identification of the Structural Transition Temperature in the Solutions of Dialkyl Sulphoxides, I 189 Diaphragm Cell Diaphragm-cell Studies of Diffusion in the Four- component System Hydrochloric Acid-Sodium Chloride-Sodium Iodide-Water, 829 Dibenzocr yptates Complexation and Transfer Free Energies of Metal-ion Dibenzocryptates, 2663 2,4-Dibromo-6-nitroaniline Oxidation of 2,4-Dibromo-6-nitroaniline in Aqueous Sulphuric Acid Solutions on a Platinum Electrode, 26 19 Dicarboxylic Acids An Electron Spin Resonance Study of Complexes of Oxovanadium(1v) with Simple Dicarboxylic Acids, 3513 1,2-Dichloroethane Binary Systems of 1,2-DichIoroethane with Benzene, Toluene, p-Xylene, Quinoline and Cyclohexane.Part 3.-Dielectric Properties and Refractive Indices at 308.15 K, 3167 Dielectric Behaviour Dielectric Behaviour of Adsorbed Water.Part 1 .-Measurement at Room Temperature on TiO,, 943 2.-Measurement at Low Temperatures on TiO,, 957 Benzene, Toluene, p-Xylene, Quinoline and Cyclohexane. Part 3.-Dielectric Properties and Refractive Indices at 308.15 K, 3 I67 The Dielectric Properties of Ethyl and Methyl Carbamates in Aqueous Solution, 841 Local Polarity of Solvent Mixtures in the Field of Electronically Excited Molecules and Exciplexes, 495 Hexacyanoferrates by Dielectric Relaxometry, Voltammetry and Spectroscopy. Prussian Blue, Congeners and Mixtures, 23 1 Electron-transfer Rates by Dielectric Relaxometry and the Direct-current Conductivities of Solid Homonuclear and Heteronuclear Mixed-valence Metal Cyanometallates and of the Methylene Blue-Iron Dithiolate Adduct, 245 Dielectric Behaviour of Adsorbed Water.Part Binary Systems of 1,2-Dichloroethane with Site-transfer Conductivity in Solid Iron Dienes Hydrogenation of Conjugated Dienes and Isomerization of Butenes on CdO, Co,O, and Crz03, 1213 Differential Thermal Analysis Hydrogen- 1 Nuclear Magnetic Resonance, Differential Thermal Analysis, X-Ray Powder Diffraction and Electrical Conductivity Studies on the Motion of Cations, including Self- diffusion in Crystals of Propylammonium Chloride and Bromide as well as their N- Deuterated Analogues, 3207 Diffusion Absence of Fast H+-ion Motion in Aqueous HCl. A Neutron Scattering Study, 687 Direct Measurement of the Diffusion Coefficients of Hydrogen Atoms in Six Gases, 751 Diaphragm-cell Studies of Diffusion in the Four- component System Hydrochloric Acid-Sodium Chloride-Sodium Iodide-Water, 829 Coefficients in Suspensions of Parallel Cylinders and Spheres, 547 Concentration Dependence of Spin Friction Diflunisal The Inclusion of Diflunisal by a- and p- Cyclodextrins. A 19F Nuclear Magnetic Resonance and Spectrophotometric Study, 2697 Diheptylsulphosuccinate Dihydrate The Crystal Structure of Sodium Diheptylsulphosuccinate Dihydrate and Comparison with Phospholipids, 3093 Formation of Superoxide during the Auto- oxidation of Anthralin (1,8-Dihydroxy-9- anthrone), 85 1 ,&Dihydroxy-9-anthroneX SUBJECT INDEX Dimethyl Sulphoxide Radical Cations of Trialkylphosphine Oxides, Trialkylphosphates, Hexamethylphosphoramide, Dimethyl Sulphoxide and various Sulphones, Sulphites and Sulphates.An Electron Spin Resonance and Radiation Chemical Study, 383 Free Energies, Enthalpies and Entropies of the Monothiocyanate Complex Formation of Trivalent Metals in Dimethyl Sulphoxide Solutions, 1253 2,3-Dimethyloxirane The Mechanism of Hydrogenolysis and Isomerization of Oxacycloalkanes on Metals. Part &-New Results on the Mechanism of Hydrogenolysis of Oxiranes on Platinum and Palladium, 2359 Dimethylpyrrolidinium Cation 1,SDiols Electrogenerated R,N(Hg), Films, 1 169 A Polarimetric, Circular Dichroism and "B Nuclear Magnetic Resonance Study of the Reaction of the Tetrahydroxyborate Ion with Two Chiral 1,3-Diols7 771 1,4-Dioxane Effect of 1,4-Dioxane on the Conductance and Ion-pairing of Hydrogen Chloride in Wet and Dry Methanol Mixtures at 25 "C, 1437 PMMA-Acetonitrile-l,4-Dioxane System, 2289 Thermodynamic Properties of the Diphoshine Disulphides Phosphorus-3 1 Nuclear Magnetic Resonance Studies of Solid Diphosphine Disulphides.Crystallographic Considerations, 1055 Diphosphonates Effect of Diphosphonates on the Precipitation of Calcium Carbonate in Aqueous Solutions, 1477 Disproportionation Chemisorption and Disproportionation of Carbon Monoxide on Palladium/Silica Catalysts of differing Percentage Metal Exposed, 2757 The Ethane- 1,2-diol-2-Methoxyethanol Solvent System. The Dependence of the Dissociation Constant of Picric Acid on the Temperature and Compositon of the Solvent Mixture, 3129 Dissociation Constant DLVO Theory Forces between Mica Surfaces in Aqueous KNO, Solution in the Range 10-4-10-' mol drn-,, showing Long-range Attraction at High Electrolyte Concentration, I703 DNA Application of Electron Spin Resonance Spectroscopy to the Study of the Effects of Ionizing Radiation on DNA and DNA Complexes, 1 Reduced Nitroimidazole Derivatives with DNA Bases, 257 Polarographic Evidence for the Interaction of Doping, Doping Effect of Sodium on y-Irradiated Magnesium Oxide, 3 107 Double Layer Forces between Mica Surfaces in Aqueous KNO, Solution in the Range IO-*-lO-' mol dm-,, showing Long-range Attraction at High Electrolyte Concentration, 1703 Effect of Neutral Polymers on the Ordering of Monodispersed Polystyrene Spheres, 2497 The Interaction between Superoxide Dismutase Doxorubicin and Doxorubicin.An Electron Spin Resonance Approach, 3669 D y e Metachromasy in Clay Minerals. Sorption of Pyronin Y by Montmorillonite and Laponite, 1685 A Dye-sensitized Photocatalyst @-Type CuCNS) for the Generation of Ocygen from Aqueous Persulphate, 2553 Effusion Mass Spectrometry Effusion Mass Spectrometric Determination of Thermodynamic Properties of the Gaseous Mono- and Di-hydroxides of Calcium and KCaO(g), 3229 Electrocatal ysis Electrocatalysis under Temkin Adsorption Conditions, 271 Mechanism of Oxygen Reactions at Porous Oxide Electrodes. Part 1 .--Oxygen Evolution at RuO, and Ru, Sn,-, 0, Electrodes in Alkaline Solution under Vigorous Electrolysis Conditions, 299 Experimental Evaluation of Adsorption Behaviour of Intermediates in Anodic Oxygen Evolution at Oxidized Nickel Surfaces, 1063 Electrochemistry Rotating-disc Electrodes.ECE and DISPl Processes, 126 1 Oxygen Evolution by Water Oxidation with Polynuclear Ruthenium Complexes, 1539 Electrode position The Study of Aluminium Deposition from Tetrahydrofuran Solutions of AlCl,-LiAlH, using Microelectrodes. Part l.-l: 1 AlC1, -LiAlH,, 2787 Tetrahydrofuran Solutions of AlCl,-LiAlH, using Microelectrodes. Part 2.-The Influence of Solution Composition, 2795 The Study of Aluminium Deposition from Electrodiffusion Transport Phenomena in Concentrated Aqueous Solutions of Sodium-Caesium Polystyrene Sulphonates, 3259 Electron Capture Electron Capture by Fe"' and (FeO,) Centres in Haemoglobin, and the Absence of Subsequent Electron Transfer from (Fe0,)- Centres to Fe"'.An Electron Spin Resonance Study, 3653 Electron Diffraction Identification of the Space Group and Detection of Cationic Ordering in Iron Antimonate using Conventional and Convergent-beam Electron Diffraction, 61 5 Electronic Spectroscopy Electron Spin Resonance and Electronic Spectroscopy of Low-spin Manganese(x1) Complexes (C,R,)(CO),(L)Mn with L = Hydrazido( 1 -), Arylamido, Anionic Nitrile and Purine-type Ligands, 3549SUBJECT INDEX xi Electron Spin Resonance Magnetic Resonance of Ultrafast Chemical Reactions. Examples from Photosynthesis, I3 A Single-crystal ENDOR Study of y-Irradiated Pyridoxine Hydrochloride, 37 An Electron Nuclear Double Resonance Study in a Glassy Matrix of Nitroxide Radicals with Delocalized Spin Density, 69 The Role of Solvent Reorganization Dynamics in Homogeneous Electron Self-exchange Reactions, 161 Supported 12-Heteropoly Acids.Part 6.-The Investigation of Reduced H,(SiW,,O,,) * x H,O and Ag,(SiW,,O,,)-x H,O and the Effects of Oxygen Adsorption, 3 1 1 5 Spectroscopy to the Study of the Effects of Ionizing Radiation on DNA and DNA Complexes, 1 Two-dimensional Transient Electron Spin Resonance Spectroscopy, 29 The Use of Electron Spin Resonance and ENDOR and TRIPLE Resonance Methods for Structural Elucidation. Isomeric 10,lO- Diphenylphenanthren-9( 1 OH)-ones, 43 Electron Spin Resonance, ENDOR and TRIPLE Resonance of some 9,lO-Anthraquinone and 9,lO-Anthraquinol Radicals in Solution, 5 1 Electron Nuclear Double Resonance of S = 1/2 Defects in a Single Crystal of the Morpholinium-TCNQ 1 : I Complex, 57 Direct Observation of a 1P-Hydrogen Shift in Vinyl Radicals derived from the Reaction of Alkynes with Thiyl Radicals, 77 Formation of Superoxide during the Auto- oxidation of Anthralin (1,8-Dihydroxy-9- anthrone), 85 Paramagnetic Adducts in the Reaction of 4- Substituted Pyridines and Phosphorus-centred Radicals, 91 Selective Formation and Conformational Analysis of Carbohydrate-derived Radicals, 95 Electron Spin Resonance Spectroscopy as an Analytical Tool, 107 Addition-Elimination Paths in Electron-transfer Reactions between Radicals and Molecules.Oxidation of Organic Molecules by the OH Radical, 113 Radical Production evidenced by Dimer Analysis in y-Irradiated Amides in Aqueous Solutions and in the Solid State, 125 An Electron Spin Resonance Study of the Radicals formed on Ultraviolet Irradiation of the Photoallergens Fentichlor and Bithionol, 135 Generation of Radicals from Antioxidant-type Molecules by Polyunsaturated Lipids, 141 Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution, 15 1 Linewidth Alternation, as a Result of Intramolecular Cation Migration, in the Electron Spin Resonance Spectrum of the 1,4- Naphthoquinone Radical Anion, 167 Electron Spin Resonance Studies of Free and Application of Electron Spin Resonance Oxygen Diffusion-Concentration in Phospholipidic Model Membranes.An Electron Spin Resonance-Saturation Study, 177 in Cells and Tissues, 191 Electron Spin Resonance of Virus and Membrane Systems, 203 Anions, 21 1 Chromatography-Electron Spin Resonance Analysis of Sugars irradiated in the Solid and Liquid Phase, 225 Trialkylphosphates, Hexamethylphosphoramide, Dimethyl Sulphoxide and various Sulphones, Sulphites and Sulphates.An Electron Spin Resonance and Radiation Chemical Study, 383 Radiation Damage in a Phosphated Sugar. An Electron Spin Resonance Study of Phosphorus- centred Radicals Trapped in an X-Irradiated Single Crystal of a Phenoxyphosphoryl Xylofuranose Derivative, 40 1 Optical and Spectromagnetical Properties of Phosphate Glasses containing Ruthenium and Titanium Ions, 705 INDO and CND0/2 Calculations for Substituted Benzene Cations, 759 Cross-relaxation of Hydrogen Atoms adsorbed on a Molybdena-Silica Catalyst, 81 3 An Electron Spin Resonance Study of Single Crystals of X-irradiated L-Ascorbic Acid at Room Temperature.Experimental Results and Semiempirical Calculations, 893 Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids. Part 5.- Elucidation of Structures of Hydrated and of Dehydrated Heteropoly Acids by Quantum Chemical Calculations of Electron Spin Resonance Parameters, 104 1 Nature of Oxide-supported Copper(i1) Ions and Copper derived from Copper(i1) Chloride, 1347 Nature of Radical Reactivity of Organic Plasma- exposed Glass Surface studied by the Electron Spin Resonance Spin-trapping Technique, 1579 Rotational Isomers of the n-Butane Radical Cation with Partially Deuterated Methyl Groups in Some Halogenated Matrices, 18 15 Radical Pairs in Single Crystals of X-Irradiated L-Ascorbic Acid at 77 K, 1869 Electron Spin Resonance Investigations of Ruthenium supported on y-Alumina, 227 1 Electron Spin Resonance Studies of HPt(CN):- and Pt(CN)i- formed by Irradiation of K, Pt(CN), in Solvents, 2803 Multiple Resonances involving Electron Spin Resonance, Nuclear Magnetic Resonance and Optical Transitions: More than Just a Game?, 3469 MAGRES: A General Program for Electron Spin Resonance, ENDOR and ESEEM, 3493 Use of Nitroxides to Measure Redox Metabolism Electron Spin Resonance and Saturation Transfer Reactions of Ozonate and Superoxide Radical High-performance Liquid Radical Cations of Trialkylphosphine Oxides, Electron Spin Resonance Characterization of An Electron Spin Resonance Study of Tripletxii SUBJECT INDEX Electron Spin Resonance (cont.) Interpretation of Electron Spin-echo Modulation for Copper(u) Complexes in Crystalline Powders, 3505 An Electron Spin Resonance Study of Complexes of Oxovanadium(1v) with Simple Dicarboxylic Acids, 3513 Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalcogenides, 3527 The Electron Spin Resonance Spectra of CpCr(CO), and CpCr(CO),P(C,H,), in Single Crystals of their Mn Analogues, 3535 An Electron Spin Resonance Study of Rutile and Anatase Titanium Dioxide Polycrystalline Powders treated with Transition-metal Ions, 354 1 Spectroscopy of Low-spin Manganese(I1) Complexes (C,R,)(CO),(L)Mn with L = Hydrazido( 1 -), Arylamido, Anionic Nitrile and Purine-type Ligands, 3549 An Electron Spin Resonance Study of Isomerism in a Coo Acetylene 7c-Complex, 3565 Binding of Paramagnetic Ions in Ionomers.Cu" and Ti3+ in Nafion Membranes, 3575 Spectromagnetic Evidence for Spatial Correlation of Copper Centres in Phosphate Glasses and its Effect on the Charge-transport Processes, 3587 Ferromagnetic Alternating Spin Chain ( S , = i, S, = $), 3603 The Electron Spin Resonance Powder Spectrum of ReIV in TiO,, 3613 Interaction of Carbon Monoxide with Ru/yAl,O,. An Electron Spin Resonance Investigation, 361 9 Oxovanadium( N) Complexes of Cysteine characterized by Electron Spin Resonance Spectroscopy, 3627 Studies of the Manganese Site of Photosystem 11 by Electron Spin Resonance Spectroscopy, 3635 Electron Capture by Fe"' and (FeO,) Centres in Haemoglobin, and the Absence of Subsequent Electron Transfer from (Fe0,)- Centres to Fe"'.An Electron Spin Resonance Study, 3653 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(I1) ",I-Macrocyclic complexes. A Means of Breaking the Co-C Bond in B12 Co-enzyme, 3663 The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach, 3669 Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution. Part 2.-Rifamycins, 3675 Nature of the Complexes formed between Copper(1r) and Glycylhistidine, 3683 A Vibronic Coupling Approach for the Interpreation of the g-Value Temperature Dependence in Type-I Copper Proteins, 3693 in Hydrocarbon Matrices, 3701 Crvstals. 3709 Electron Spin Resonance and Electronic Electron Spin Resonance Spectra of a An Electron Spin Resonance Investigation of the The Electron Spin Resonance Spectrum of AI[C,H,] N; and (CN); Spin-Lattice Relaxation in KCN Single-crystal Proton ENDOR of the SO; Centre Single-crystal Electron Spin Resonance Studies in in ?-Irradiated Sulphamic Acid, 37 17 Radiation-produced Species in Ice I,.Part 1.-The 0- Radicals, 3725 Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals, 3737 Single-crystal Electron Spin Resonance Studies on Electron Transfer The Role of Solvent Reorganization Dynamics in Homogeneous Electron Self-exchange Reactions, 161 Electron-transfer Rates by Dielectric Relaxometry and the Direct-current Conductivities of Solid Homonuclear and Heteronuclear Mixed-valence Metal Cyanometallates and of the Methylene Blue-Iron Dithiolate Adduct, 245 Corrosion Processes in Quantized Semiconductor Colloids studied by Pulse Radiolysis, 1127 Electron-transfer Reactions on CdSe Colloids as studied by Pulse Radiolysis, 1193 The Role of Electron Transfer Processes in Determining Desorption Kinetics, 1363 Comparison between Heterogeneous and Homogeneous Electron Transfer in p- Phenylenediamine Systems, 2727 Radical Spectra and Product Distribution following Electrophilic Attack by the OH' Radical on 4-Hydroxybenzoic Acid and Subsequent Oxidation, 3177 Electron Capture by FerI1 and (FeO,) Centres in Haemoglobin, and the Absence of Subsequent Electron Transfer from (Fe0,)- Centres to Fe"'.An Electron Spin Resonance Study, 3653 Electron-donor-Electron-acceptor Association Electron-donor-Electron-acceptor Complexes Constants of Pyrene with 2,4,6-Trinitrotoluene in Solution determined by 'H-Nuclear Magnetic Resonance from Non-linear Scatchard Plots, 2641 Electronic Absorption Spectroscopy A Kinetic Study of the Self-reaction of Prop-2- ylperoxyl Radicals in Solution using Ultraviolet Absorption Spectroscopy, 1805 Electron-transfer Reactions Addition-Elimination Paths in Electron-transfer Reactions between Radicals and Molecules.Oxidation of Organic Molecules by the OH Radical, 113 Electrostatic Interactions Electrostatic Interactions and their Role in Coadsorption Phenomena, 1935 Electrostriction The Molar Volume of a Large Polymeric Cation [A~130,0H481", 1725 Kinetics of Particle Growth, 1449 Emulsion Emulsion Polymerization of Butyl Acrylate.ENDOR A Single-crystal ENDOR Study of y-Irradiated Pyridoxine Hydrochloride, 37 The Use of Electron Spin Resonance and ENDOF and TRIPLE Resonance Methods for Structura Elucidation. Isomeric 10,lO- Di~henvl~henanthren-9( 1 OHbones. 43... SUBJECT INDEX Xlll ENDOR (cont.) Electron Spin Resonance, ENDOR and TRIPLE Resonance of some 9,lO-Anthraquinone and 9,lO-Anthraquinol Radicals in Solution, 51 An Electron Nuclear Double Resonance Study in a Glassy Matrix of Nitroxide Radicals with Delocalized Spin Density, 69 Multiple Resonances involving Electron Spin Resonance, Nuclear Magnetic Resonance and Optical Transitions: More than Just a Game?, 3469 MAGRES: A General Program for Electron Spin Resonance, ENDOR and ESEEM, 3493 Electron Nuclear Double Resonance of S = 1/2 Defects in a Single Crystal of the Morpholinium-TCNQ 1 : 1 Complex, 57 in ?-Irradiated Sulphamic Acid, 371 7 Single-crystal Proton ENDOR of the SO, Centre Enthalpy Enthalpies of Transfer of Tetra-alkylammonium Halides from Water to Water-Propan- 1-01 Mixtures at 25 "C, 2585 Compounds, 1553 Thermodynamic Stability of Solid Intermolecular Equilibrium Constants Hydrogen Bonding.Part 2.-Equilibrium Constants and Enthalpies of Complexation for 72 Monomeric Hydrogen-bond Acids with N- Methylpyrrolidinone in 1 , 1 , 1-Trichloroethane, 2867 Erbium Dicarboxylates Estimations of Stability Constants by Potentiometry of some Lanthanum and Erbium Dicarboxylates at Constant Ionic Strength, 425 ESCA Catalysis by Amorphous Metal Alloys. Part 6.-Factors controlling the Activity of Skeletal Nickel Catalysts prepared from Amorphous and Crystalline Ni-Zr Powder Alloys, 2883 Escherichia coli Microcalorimetric Measurement of the Enthalpies of Transfer of a Series of ortho- and para- Alkoxyphenols from Water to Octan- 1-01 and from Isotonic Solution to Escherichia coli Cells, 2705 ESEEM MAGRES: A General Program for Electron Spin Resonance, ENDOR and ESEEM, 3493 Ethane Kinetics and Mechanism of Oxidative Dehydrogenation of Ethane and Small Alkanes with Nitrous Oxide over Cobalt-doped Magnesium Oxide, 3139 Ethane-1,2-dioi The Ethane- 1,2-di01-2-Methoxyethanol Solvent System.The Dependence of the Dissociation Constant of Picric Acid on the Temperature and Compositon of the Solvent Mixture, 3129 Ethanol Ethanol Promotion by the Addition of Cerium to Rhodium-Silica Catalysts, 21 19 Reactive Intermediates for the Ethene Ethene Homologation Reaction on Molybdena-Silica Catalysts, 1859 Alkali Metal, Chlorine and other Promoters in the Silver-catalysed Selective Oxidation of Ethylene, 2035 Ethidium Bromide Fluorescence of Ethidium in Alcohol-Water Solutions, 1609 Ethyl Carbamate The Dielectric Properties of Ethyl and Methyl Carbamates in Aqueous Solution, 841 Ethyl Iodide Theoretical Analysis of Activation Parameters in Mixed Solvents Involving Various Chemical Equilibria.Reaction of Ethyl Iodide with Bromide Ion in N-Methylacetamide-Acetonitrile and N-Methylacetamide-N,N,- Dimethylacetamide Mixtures, 1089 EXAFS Local Structure of Nickel Oxide grown at High Structure of the Catalytic Site on the Silica- Temperatures in Ceramic Electrolyte Cells, 289 supported Catalyst derived from Copper(I1) Acetate, 1227 Excess Gibbs Functions Pairwise Gibbs Function Cospherexosphere Group Interaction Parameters for Alkylammonium Salts in Aqueous Solutions at 298 K; Solubilities of Hydrocarbons in Aqueous Salt Solutions, 3039 Excess Volumes Refractive Index and Excess Volume for Binary Liquid Mixtures.Part 1 .-Analyses of New and Old Data for Binary Mixtures, 2449 Exciplex Local Polarity of Solvent Mixtures in the Field of Electronically Excited Molecules and Exciplexes, 495 Faujasite Non-isothermal Reduction Kinetics and Reducibilities of Nickel and Cobalt Faujasites, 3015 Fentichlor An Electron Spin Resonance Study of the Radicals formed on Ultraviolet Irradiation of the Photoallergens Fentichlor and Bithionol, 135 Ferrierite One-dimensional Rare Gases in the Pores of Ferrierite and their Virial Coefficients, 33 17 Ferrites Iron(i1) Cobalt Ferrites.Preparation and Interfacial Behaviour, 1 159 Ferroelectrics The Ferroelectric and Liquid-crystalline Properties of Some Chiral Alkyl 4-n-Alkanoyloxybiphenyl- 4'-carboxylates, 3429 Ferromagnetic Chain Electron Spin Resonance Spectra of a Ferromagnetic Alternating Spin Chain (S, = Gi, S , = i), 3603 Flash Photolysis Direct Observation of a 1,4-Hydrogen Shift in Vinyl Radicals derived from the Reaction of Alkynes with Thiyl Radicals, 77 Fluorescein Rotating-disc Electrodes. ECE and DISPl Processes, 126 1xiv SUBJECT INDEX Fluorescence Characterisation of Aerosol OT-stabilised Oil-in- water Microemulsions using a Time-resolved Fluorescence Method, 1493 Fluorescence of Ethidium in Alcohol-Water Solutions, 1609 Solvent and Substituent Effects on Intramolecular Charge Transfer of Selected Derivatives of 4- Trifluoromethyl-7-aminocoumarin, 2533 Fluorescence Quenching as a Probe of Size Domains and Critical Fluctuations in Water-in- oil Microemulsions, 1007 Four-component System Diaphragm-cell Studies of Diffusion in the Four- component System Hydrochloric Acid-Sodium Chloride-Sodium Iodide-Water, 829 Fourier-transform Infrared Spectroscopy A Study of the Adsorption Sites on Thoria by Scanning Transmission Electron Microscopyand Fourier-transform Infrared Spectroscopy.Adsorption and Desorption of Water and Methanol, 1417 Fractal Dimension Self-consistency of the Percolation Model as applied to a Macrofluid-like Water-in-Oil Microemulsion, 162 I Free Energies of Transfer Ionic Solvation in Water-Cosolvent Mixtures.Part I4.-Free Energies of Transfer of Single Ions from Water into Water-Ethylene Carbonate and Water-Propylene Carbonate Mixtures, 128 1 Benzonitrile derived from Solubility and Complexing Data, 1569 Single-ion Free Energies for Transfers to Free Heteropoly Acids Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids. Part 6.-The Investigation of Reduced H,(SiW,,O,,).x H,O and Ag,(SiW,,O,,)~x H,O and the Effects of Oxygen Adsorption, 3 1 15 Gadolinium Zironate Electrical and Catalytic Properties of some Oxides with the Fluoriteor Pyrochlore Structure. CO Oxidation on some Compounds derived from Gd,Zr,O,, 1485 Gas Chromatography Conversion, 177 1 Comments on the Mechanism of MTG/HZSM-5 Gas Sensors Tin Dioxide Gas Sensors.Part 1.-Aspects of the Surface Chemistry revealed by Electrical Conductance Variations, 1323 GasSolid Chromatography Adsorption of Thiophene and Model Hydrocarbons on MoOJy-Al,O, Catalysts studied by Gas-Solid Chromatography, 1179 A New Pressure-programmed Volumetric Method GasSolid Interface of Measuring Adsorption at the Gas-Solid Interface, 2693 Gibbs-Duhem Equation A New Analytical Solution of the Quaternary Gibbs-Duhem Equation, 3367 Glasses Optical and Spectromagnetical Properties of Phosphate Glasses containing Ruthenium and Titanium Ions, 705 GI yc ylhistidine An Electron Spin Resonance Investigation of the Nature of the Complexes formed between Copper(I1) and Glycylhistidine, 3683 Gold Photochemical Formation of Colloidal Metals, A Comparison of the Effects of Cu and Au on the 1559 Surface Reactivity of Ru(0001), 1975 y-Radio1 ysis Single-crystal Proton ENDOR of the SO; Centre Wetting of Graphite (0001) by Carbon Monoxide.A Stepwise Adsorption Isotherm Study, 3355 Structure of Second-stage Graphite-Rubidium, C,,Rb, 3447 in y-Irradiated Sulphamic Acid, 37 17 Graphite Haemoglo bin Electron Capture by Fe"' and (FeO,) Centres in Haemoglobin, and the Absence of Subsequent Electron Transfer from (Fe0,)- Centres to Fe"'. An Electron Spin Resonance Study, 3653 Hemimicelle Hemimicelle Formation of Cationic Surfactants at Silica Gel-Water Interface, 2671 Heteropoly Acids Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids. Part 5.- Elucidation of Structures of Hydrated and of Dehydrated Heteropoly Acids by Quantum Chemical Calculations of Electron Spin Resonance Parameters, 104 1 Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids. Part 6.-The Investigation of Reduced H,(SiW,,O,,) ' x H,O and Ag,(SiW,,O,,).x H,O and the Effects of Oxygen Adsorption, 3 1 15 n-Hexadecanoic Acid The Liquid-Vapour Transition in Monolayers of n-Pentadecanoic Acid at the Air/Water Interface, 585 Hexane Thermodynamics of Mixtures with a Hexane Isomer.Excess Volumes of l-Chlorohexane with a Hexane Isomer at 298.15 K, 819 High-Performance Liquid Chromatography High-performance Liquid Chromatography-Electron Spin Resonance Analysis of Sugars irradiated in the Solid and Liquid Phase, 225 Homologation Reactive Intermediates for the Ethene Homologation Reaction on Molybdena-Silica Catalysts, 1859 Hydration The Thermodynamics of Solvation of Ions. Part 2.-The Enthalpy of Hydration at 298.15 K, 339 Micellar Solutions, 2847 The Hydration of Aliphatic Aldehydes in Aqueous Hydrazine Hydrazine Reduction of Transition-metal Oxides, 327 1SUBJECT INDEX xv 4Hydrobenzoic Acid Radical Spectra and Product Distribution following Electrophilic Attack by the OH' Radical on 4-Hydroxybenzoic Acid and Subsequent Oxidation, 3 177 Hydrocarbons Formation of Hydrocarbons from CO + H, using a Cobalt-Manganese Oxide Catalyst. A I3C Isotopic Study, 2963 H ydrodesulphurisation The Role of Co in Sulphidised CwMo Hydrodesulphurisation Catalysts supported on Carbon and Alumina, 2145 Inorganic Cluster Compounds as Models for the Structure of Active Sites in Promoted Hydrodesulphurisation Catalysts, 2 157 Hydrogen Direct Measurement of the Diffusion Coefficients of Hydrogen Atoms in Six Gases, 751 Ultraviolet-Visible Reflectance Studies of Hydrogen Adsorption and CO-H, Interaction at MgO and CaO Surfaces, 1237 Aspects of Temperature-programmed Analysis of some Gas-Solid Reactions.Part 2.-Hydrogen Temperature-programmed Desorption from Silica-supported Platinum, 1369 Photogeneration of Hydrogen from Water over an Alumina-supported ZnS-CdS Catalyst, 1395 An X-Ray Photoelectron Spectroscopy Study of the Influence of Hydrogen on the Oxygen-Silver Interaction, 3161 Mechanism of Oxygen Reactions at Porous Oxide Electrodes.Part 1 .--Oxygen Evolution at RuO, and Ru, Sn,-, 0, Electrodes in Alkaline Solution under Vigorous Electrolysis Conditions, 299 Isothermal Titration of Supported Platinum. Part 1 .--CO-O, Titration, 165 1 Isothermal Titration of Supported Platinum. Part 2.-Alkene Titration using Cyclohexene, 1667 Hydrogen Bonding Basicity of Water in Dipolar Aprotic Solvents using the 1,4,8,1 l-Tetramethyl-1,4,8,1 l-tetra- azacyclotetradecaneNickel(I1) Cation as a Probe of Electron-pair Acceptance, 1641 Infrared Spectroscopic Studies of Hydrogen Bonding in Triethylammonium Salts. Part 4.-Rearrangement of Hydrogen-bonded Ion Pairs of Triethylammonium Salts caused by Interaction with Tetrabutylammonium Salts in Solution, 1879 35Cl Nuclear Quadrupole Resonance and Infrared Spectroscopic Studies of Hydrogen Bonding in Complexes of Trichloroacetic Acid with Various Nitrogen and Oxygen Bases, 2541 Constants and Enthalpies of Complexation for 72 Monomeric Hydrogen-bond Acids with N- Methylpyrrolidinone in 1, 1, 1-Trichloroethane, 2867 Diheptylsulphosuccinate Dihydrate and Comparison with Phospholipids, 3093 The Effect of Hydrogen Sulphide on the Hydrogen Bonding.Part 2.-Equilibrium The Crystal Structure of Sodium Hydrogen Sulphide Adsorption and Thermal Desorption of Carbon Monoxide over Rhodium Catalysts, 1835 Influence of Lithium on Reduction, Dispersion and Hydrogenation Activity of Nickel on Alumina Catalysts, 733 Hydrogenation of Carbon Monoxide and Carbon Dioxide catalysed by Supported Ruthenium Clusters derived from Ru,(CO),, and from H4R~4(C0)12, 905 Hydrogenation of CO, over Co/Cu/K Catalysts, 171 1 Catalysis by Amorphous Metal Alloys.Part 7.-Formation of Fine Fe Particles on the Surface of an Alloy in the Precrystallisation State prepared from an Amorphous Fes,Zrl, Powder Alloy, 2895 Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia, 3069 H ydr ogenol ysis Hydrogenation Chemisorption and Catalysis by Metal Clusters. Effects of the Oxidation State of Cerium on the Reactivity and Sulphur Resistance of Nio/ Zeolite, Nio/Silica and Nio/CeO, Catalysts in Butane Hydrogenolysis, 1137 Isomerization of Oxacycloalkanes on Metals. Part &--New Results on the Mechanism of Hydrogenolysis of Oxiranes on Platinum and Palladium, 2359 Kinetic Modelling of Multiple-site Activity and the Kinetics of Inhibition Reactions in the Hydrogenolysis of C,H, on a Nickel Wire Catalyst, 2825 The Mechanism of Hydrogenolysis and Hydrolysis Kinetics of Hydrolysis of Phenyl Dichloroacetates Micellar Effects upon the Reactions of Complex in Aqueous Salt Solutions, 865 Ions in Solution.Retardation of the Base Hydrolysis of cis- (Azido)(imidazole)bis(ethylenediamine)cobalt( 111) by Sodium Dodecyl Sulphate, 1307 Hydroxide Ion Kinetics of Reaction with Hydroxide Ions and Solubilities of Iron(I1) Complex Cations in Aqueous Urea Solutions. Derivation of Transfer Chemical Potentials for Initial and Transition States, 559 Hydroxy-l,4naphthoquinones Oxygen Reduction with Hydroxy- 1,4- naphthoquinones immobilized at Carbon Electrodes, 1823 Ice Single-crystal Electron Spin Resonance Studies in Radiation-produced Species in Ice I,.Part 1.-The 0- Radicals, 3725 Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals, 3737 Single-crystal Electron Spin Resonance Studies on Inclusion The Inclusion of Diflunisal by a- and p- Cyclodextrins. A "F Nuclear Magnetic Resonance and Spectrophotometric Study, 2697xvi SUBJECT INDEX Inclusion (cont.) The Inclusion of Tropaeolin OOO No. 2 by Permethylated p-Cyclodextrin. A Kinetic and Equilibrium Study, 275 1 Cyclodextrin. A Kinetic and Equilibrium Study, 3237 The Inclusion of Pyronine Y by p- and y- indium Free Energies, Enthalpies and Entropies of the Monothiocyanate Complex Formation of Trivalent Metals in Dimethyl Sulphoxide Solutions, 1253 infrared Spectroscopy Adsorption and Dissociation of Ammonia on the Hydroxylated Surface of Magnesium Oxide Powders, 477 Modified with Fluoride Anions, 535 Structures of Vanadium Oxide on Various Supports, 675 Potassium 5-Hexenoate and Conformational Change on Micellization, 789 A Fourier-transform Infrared and Catalytic Study of the Evolution of the Surface Acidity of Zirconium Phosphate following Heat Treatment, 853 Zeolite Lewis Sites in Methanol Reactions over HZSM-5 Surfaces, 1149 Infrared Spectroscopic Study of Catalytic Activity of Rh/TiO, for the CO + H, Reaction, 1427 Structural Effects on the Adsorption of Alcohols on Titanium Dioxides, 1591 Basicity of Water in Dipolar Aprotic Solvents using the 1,4,8,1 I-Tetramethyl- 1,4,8,1 l-tetra- azacyclotetradecaneNickel(x1) Cation as a Probe of Electron-pair Acceptance, 1641 Origin of Boron Mobility over Boron-impregnated ZSM-5.A Combined High-resolution-Solid- state IIB Nuclear Magnetic Resonance/Infrared Spectral Investigation, 1751 Catalytic Activity and Structure of Mo Oxide Highly Dispersed on ZrO, for Oxidation Reactions, 176 1 Comments on the Mechanism of MTG/HZSM-5 Conversion, 1771 Infrared Spectroscopic Studies of Hydrogen Bonding in Triethylammonium Salts. Part 4.-Rearrangement of Hydrogen-bonded Ion Pairs of Triethylamrnonium Salts caused by Interaction with Tetrabutylammonium Salts in Solution, 1879 35Cl Nuclear Quadrupole Resonance and Infrared Spectroscopic Studies of Hydrogen Bonding in Complexes of Trichloroacetic Acid with Various Nitrogen and Oxygen Bases, 2541 Characterization of CO-Rh species formed on Rh- Y Zeolite by Temperature-programmed Desorption and Infrared Techniques, 2605 Infrared Studies on Dinitrogen and Dihydrogen adsorbed over TiO, at Low Temperatures, 2765 Infrared Study of the Adsorption of Non-ionic Surfactants on Silica, 3283 Catalytic Properties of Synthetic Faujasites Fourier-transform Infrared Investigation of Vibrational Spectra of Potassium 4-Pentenoate and Fourier-transform Infrared Study of the Role of Infrared Study of the Desorption of Polycondensed Aromatic Compounds by Non- ionic Surfactants at the Silica-Carbon Tetrachloride Interface, 3295 Tin Oxide Surfaces. Part 17.-An Infrared and Thermogravimetric Analysis of the Thermal Dehydration of Tin(1v) Oxide Gel, 3383 Intercalation Smectite Molecular Sieves.Part 2.-Expanded Fluorhectorite Sorbents, 779 Synthesis of Montmorillonite-Viologen Intercalation Compounds and their Photochromic Behaviour, 185 1 C,,Rb, 3447 Structure of Second-stage Graphite-Rubidium, Interfaces Hemimicelle Formation of Cationic Surfactants at Silica Gel-Water Interface, 267 1 Interfacial Tension Interfacial Tension Minima in Oil-Water-Surfactant Systems. Effects of Cosurfactant in Systems containing Sodium Dodecyl Sulphate, 2347 Intermetallic Compounds The Use of Hydride-forming Rare-earth-Cobalt Intermetallic Compounds in the Dehydrogenation of Propan-2-01, 743 Intermolecular Compounds Compounds, 1 5 5 3 Thermodynamic Stability of Solid Intermolecular Internal Pressures Internal Pressures, Temperatures of Maximum Density and Related Properties of Water and Deuterium Oxide, 1783 internuclear Potential Ground-state Reduced Potential Curves (RPC) of Non-metallic First- and Second-row Hydrides, 2857 Intersecting-state Model Solvent-exchange Reactions of Metal Ions.Diagnosis of Mechanisms in Terms of the Bond Order of the Activated Complexes, 431 Intradiffusion Coefficients Transport Phenomena in Concentrated Aqueous Solutions of Sodiumxaesium Polystyrene Sulphonates, 3259 Ion Exchange Dealumination of Sodium Y Zeolite with Sodium Ion Exchange on the 1,4,7,10,13,16- Hydrochloric Acid, 153 1 Hexaoxaoctadecanesodium(1) Cation (“a. 18C61 +) in Several Solvents. A Sodium-23 Nuclear Magnetic Resonance Study, 2459 Electrochemical Properties of Cation Exchange Membranes, 284 1 Thermodynamic Properties of Concentrated Heteroionic Polyelectrolyte Solutions, 3249 Investigation of Internal Silanol Groups as Structural Defects in ZSM-5-type Zeolites, 3459 Ionic Solvation Ionic Solvation in Water-Cosolvent Mixtures.Part 13.-Free Energies of Transfer of Single Ions from Water into Water-Tetrahydrofuran Mixtures, 439SUBJECT INDEX xvii Ionic Solvation (cont.) Ionic Solvation in Waterxosolvent Mixtures. Part I4.--Free Energies of Transfer of Single Ions from Water into Water-Ethylene Carbonate and Water-Propylene Carbonate Mixtures, 128 1 Ionization Equilibria in Solutions of Cobalt(n) Ionization Equilibria Thiocyanate in N,N-Dimethylformamide, 226 1 Ion-pair Formation by Tetra-alkylammonium Ions in Methanol.A Nuclear Magnetic Resonance Study, 3419 Ion-pair Formation Ion-selective Electrodes Standard Gibbs Free Energies of Transfer of NaCl and KCl from Water to Mixtures of the Four Isomers of Butyl Alcohol with Water. The Use of Ion-selective Electrodes to Study the Thermodynamics of Solutions, 635 Iridium Reaction of Neopentane with Hydrogen over Pd, Pt, Ir and Rh, 1293 Iron Kinetics of Metal Oxide Dissolution. Oxidative Dissolution of Chromium from Mixed Nickel-Iron-Chromium Oxides by Permanganate, 37 1 sieve Structures. Ferrisilicate Analogues of Zeolite ZSM-5, 487 Iron(r1) Cobalt Ferrites. Preparation and Interfacial Behaviour, 1 159 An In Situ Mossbauer Spectroscopic Investigation of Titania-supported Iron-Ruthenium Catalysts, 2573 An Electron Spin Resonance Study of Rutile and Anatase Titanium Dioxide Polycrystalline Powders treated with Transition-metal Ions, 3541 Identification of the Space Group and Detection of Cationic Ordering in Iron Antimonate using Conventional and Convergent-beam Electron Diffraction, 61 5 Iron Chloride Solution, 1507 Hexacyanoferrates by Dielectric Relaxometry, Voltammetry and Spectroscopy.Prussian Blue, Congeners and Mixtures, 23 1 Kinetics of Reaction with Hydroxide Ions and Solubilities of Iron(n) Complex Cations in Aqueous Urea Solutions. Derivation of Transfer Chemical Potentials for Initial and Transition States, 559 Light-induced Hydrogen Formation and Photo- uptake of Oxygen in Colloidal Suspensions of a- Fe,O,, 1101 Incorporation and Stability of Iron in Molecular- Kinetics of Pyrrole Polymerisation in Aqueous Site-transfer Conductivity in Solid Iron Isomerization Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia, 3069 The Mechanism of Hydrogenolysis and Isomerization of Oxacycloalkanes on Metals.Part 8.-New Results on the Mechanism of Hydrogenolysis of Oxiranes on Platinum and Palladium, 2359 Isotope Exchange Exchange of Oxygen Isotopes between Carbon Dioxide and Ion-exchanged Zeolites A, 41 1 Surface Reactivity and Spectroscopy of Alkaline- earth Oxide Powders. Part 3.-lH/'H and 180/160 Exchange on Specpure CaO, 2973 Cobalt-Manganese Oxide Catalyst. A 13C Isotopic Study, 2963 Formation of Hydrocarbons from CO + H, using a Kinetics Kinetics of Metal Oxide Dissolution. Oxidative Dissolution of Chromium from Mixed Nickel-Ironchromium Oxides by Permanganate, 37 1 Kinetics of Hydrolysis of Phenyl Dichloroacetates in Aqueous Salt Solutions, 865 A Phenomenological Approach to Micellisation Kinetics, 967 The Role of Electron Transfer Processes in Determining Desorption Kinetics, 1363 A Kinetic Study of the Self-reaction of Prop-2- ylperoxyl Radicals in Solution using Ultraviolet Absorption Spectroscopy, I805 Part 1.-A Kinetic Study of Self-reactions of 2- Propylperoxyl Radicals between 135 and 300 K, 242 1 Part 2.-A Kinetic and Product Study of Self- reactions of 2-Propylperoxyl Radicals between 253 and 323 K, 2433 Effect of Solvent on the Reactions of Coordination Complexes.Part 1 .-Kinetics of Solvolysis of the cis- (Bromo)(benzimidazole)bis(ethylenediamine)cobalt( II in Methanol-Water Media, 2505 Kinetics and Mechanism of Oxidative Dehydrogenation of Ethane and Small Alkanes with Nitrous Oxide over Cobalt-doped Magnesium Oxide, 3 139 Reactions of Alkylperoxyl Radicals in Solution.Reactions of Alkylperoxyl Radicals in Solution. Lanthanum Temperature-programmed Desorption Study of the Interactions of H,, CO and CO, with LaMnO,, 3149 Process of Preparation of Rhodium/Lanthana Catalysts, 2279 Potentiometry of some Lanthanum and Erbium Dicarboxylates at Constant Ionic Strength, 425 Study of the Support Evolution through the Estimations of Stability Constants by Laponite Metachromasy in Clay Minerals. Sorption of Pyronin Y by Montmorillonite and Laponite, 1685 Light Scattering Thermodynamic Properties of the PM M A-Acetonitrile- 1,4- Dioxane System, 2289 Temperature in the Solutions of Dialkyl Sulphoxides, 1 189 Self-consistency of the Percolation Model as applied to a Macrofluid-like Water-in-Oil Microemulsion, I62 1 Identification of the Structural Transitionxviii SUBJECT INDEX Lipids Generation of Radicals from Antioxidant-type Molecules by Polyunsaturated Lipids, 141 Liquid Crystals The Ferroelectric and Liquid-crystalline Properties of Some Chiral Alkyl 4-n-Alkanoyloxybiphenyl- 4'-carboxylates, 3429 Lithium Influence of Lithium on Reduction, Dispersion and Hydrogenation Activity of Nickel on Alumina Catalysts, 733 Monovalent Cations in Molten LiAlCl,, 2925 Tetrahydrofuran Solutions of AlC1,-LiAlH, using Microelectrodes.Part 2.-The Influence of Solution Composition, 2795 Lithium Ions, Chloride Ions and Water in Aqueous Lithium Chloride Solutions, I779 Intermolecular Structure around Lithium The Study of Aluminium Deposition from Measurements of Tracer Diffusion Coefficients of Low-dimensional Materials Electron Spin Resonance Spectra of a Ferromagnetic Alternating Spin Chain (S, = i, S, = i), 3603 Magic-angle Spinning Nuclear Magnetic Resonance spectroscopy Investigation of Internal Silanol Groups as Determination of the Distribution of Aluminium Structural Defects in ZSM-5-type Zeolites, 3459 in Zeolitic Frameworks, 268 1 Magnesium Adsorption and Dissociation of Ammonia on the Hydroxylated Surface of Magnesium Oxide Powders, 477 Magnesium Oxide, 72 1 Magnesium Oxide, 3 107 Dynamic Kinetics of CO Oxidation over Doping Effect of Sodium on y-Irradiated Magnetic Relaxation Coupled 13C Longitudinal and Transverse Magnetic Relaxation in Micellar and Non- micellar Sodium Octanoate, 2593 Magnetic Susceptibilities Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalcogenides, 3527 MAGRES MAGRES: A General Program for Electron Spin Resonance, ENDOR and ESEEM, 3493 Manganese The Electron Spin Resonance Spectra of CpCr(CO), and CpCr(CO),P(C,H,), in Single Crystals of their Mn Analogues, 3535 Electron Spin Resonance and Electronic Spectroscopy of Low-spin Manganese(I1) Complexes (C,R,)(CO),(L)Mn with L = Hydrazido( 1 -), Arylamido, Anionic Nitrile and Purine-type Ligands, 3549 Studies of the Manganese Site of Photosystem I1 by Electron Spin Resonance Spectroscopy, 3635 Manometry The Liquid-Vapour Transition in Monolayers of n-Pentadecanoic Acid at the Air/Water Interface, 585 Mass Spectrometry Direct Measurement of the Diffusion Coefficients Heterogeneous Decomposition of of Hydrogen Atoms in Six Gases, 751 Trichlorofluoromethane on Carbonaceous Surfaces, 3055 Conversion, 177 1 Comments on the Mechanism of MTG/HZSM-5 Matrices The Electron Spin Resonance Spectrum of Al[C,H,] in Hydrocarbon Matrices, 3701 An Electron Nuclear Double Resonance Study in a Glassy Matrix of Nitroxide Radicals with Delocalized Spin Density, 69 Electron Spin Resonance Characterization of Rotational Isomers of the n-Butane Radical Cation with Partially Deuterated Methyl Groups in Some Halogenated Matrices, 18 15 Membrane Electron Spin Resonance and Saturation Transfer Electron Spin Resonance of Virus and Membrane Systems, 203 Model Membranes.An Electron Spin Resonance-Saturation Study, I77 Binding of Paramagnetic Ions in Ionomers. Cu2+ and Ti3+ in Nafion Membranes, 3575 Oxygen Diffusion-Concentration in Phospholipidic Mercury Medium Effect on the Electrochemical Behaviour of the Cd"/Cd (Hg) System in Propane-1,2- diol-Water Mixtures, 28 13 Electrogenerated R,N(Hg), Films, 1 169 Metachromasy in Clay Minerals. Sorption of Metachomas y Pyronin Y by Montmorillonite and Laponite, 1685 Metal Clusters Chemisorption and Catalysis by Metal Clusters. Hydrogenation of Carbon Monoxide and Carbon Dioxide catalysed by Supported Ruthenium Clusters derived from Ru,(CO),, and from H,Ru,(CO),,, 905 Metal Cyanometallates Electron-transfer Rates by Dielectric Relaxometry and the Direct-current Conductivities of Solid Homonuclear and Heteronuclear Mixed-valence Metal Cyanometallates and of the Methylene Blue-Iron Dithiolate Adduct, 245 Metal Films Adsorption, Decomposition and Surface Reactions of Methyl Chloride on Metal Films of Iron, Nickel, Palladium, Lead, Gold and Copper, 239 1 Metal Oxides Kinetics of Metal Oxide Dissolution.Oxidative Dissolution of Chromium from Mixed Nickel-Iron-Chromium Oxides by Permanganate, 37 1 Comparison of Radiation-generated and Chemically-generated RuO, . 2H20 and MnO, Colloids, 300 1 Redox Reactions with Colloidal Metal Oxides.YUBJEL 1 Metal-organic Chemical Vapour Deposition Metal-organic Chemical Vapour Deposition (MOCVD) of Compound Semiconductors. Part 2.-Preparation of ZnSe Epitaxial Layers on (100) Oriented GaAs Single-crystalline Substrates, 323 MetalSupport Interactions Influence of Metal-Support Interactions on the Hydrogenolysis of Methylcyclopentane over Supported Rh Catalysts, 9 13 Methane Hydrocarbon Formation from Methylating Agents over the Zeolite Catalyst ZSM-5.Comments on the Mechanism of Carbon-Carbon Bond and Methane Formation, 57 1 ZSM-5 containing Co-adsorbed Benzene, and the Location of the Benzene Molecules, 2301 Photoinduced Reactions of Methane with Molybdena Supported on Silica, 238 1 Oxidative Coupling of Methane over Samarium Oxides Using N,O as the Oxidant, 13 15 Molecular Mobility of Methane adsorbed on Methanol Fourier-transform Infrared Study of the Role of Zeolite Lewis Sites in Methanol Reactions over HZSM-5 Surfaces, 1149 Ion-pairing of Hydrogen Chloride in Wet and Dry Methanol Mixtures at 25 "C, 1437 Nuclear Magnetic Resonance Self-diffusion Studies of Methanol-Water Mixtures in Pentasil-type Zeolites, 1843 Promotion of Platinum-based Catalysts for Methanol Synthesis from Syngas, 21 13 Promotion of Methanol Synthesis and the Water- gas Shift Reactions by Adsorbed Oxygen on Supported Copper Catalysts, 2 193 The Promoting Role of Cr and K in Catalysts from High-pressure and High- temperature Methanol and Higher-alcohol Synthesis, 2213 Ion-pair Formation by Tetra-alkylammonium Ions in Methanol.A Nuclear Magnetic Resonance Study, 3419 Effect of 1,4-Dioxane on the Conductance and 2-Methox yethanol The Ethane- 1,2-di01-2-Methoxyethanol Solvent System.The Dependence of the Dissociation Constant of Picric Acid on the Temperature and Compositon of the Solvent Mixture, 3129 The Dielectric Properties of Ethyl and Methyl Methyl Carbamate Carbamates in Aqueous Solution, 841 Methyl Chloride Adsorption, Decomposition and Surface Reactions of Methyl Chloride on Metal Films of Iron, Nickel, Palladium, Lead, Gold and Copper, 239 1 Methyl Orange Methyl Orange as a Probe of the Semiconductor-Electrolyte Interfaces in CdS Suspensions, 2647 Methyl Viologen The Two-electron Oxidation of Methyl Viologen. Detection and Analysis of Two Fluorescing Products, 2559 Methylcellulose Kinetics of Pyrrole Polymerisation in Aqueous Iron Chloride Solution, 1507 Methylcyclopentane Influence of Metal-Support Interactions on the Hydrogenolysis of Methylcyclopentane over Supported Rh Catalysts, 9 I3 N-Meth ylp yrrolidinone Hydrogen Bonding.Part 2.-Equilibrium Constants and Enthalpies of Complexation for 72 Monomeric Hydrogen-bond Acids with N- Methylpyrrolidinone in 1 , 1,l -Trichloroethane, 2867 Mica Forces between Mica Surfaces in Aqueous KNO, Solution in the Range 10-4-10-' mol dm-3, showing Long-range Attraction at High Electrolyte Concentration, 1703 Micelle A Phenomenological Approach to Micellisation Micellar Effects upon the Reactions of Complex Kinetics, 967 Ions in Solution. Retardation of the Base Hydrolysis of cis- (Azido)(imidazole)bis(ethylenediamine)cobalt( 111) by Sodium Dodecyl Sulphate, 1307 The Hydration of Aliphatic Aldehydes in Aqueous Micellar Solutions, 2847 Micelle Formation of Ionic Amphiphiles.Thermochemical Test of a Thermodynamic Model, 3331 Surface Potential Measurements in Pentanol- Sodium Dodecyl Sulphate Micelles, 59 1 Coupled 13C Longitudinal and Transverse Magnetic Relaxation in Micellar and Non- micellar Sodium Octanoate, 2593 A Small-angle Neutron Scattering Investigation of Rod-like Micelles aligned by Shear Flow, 2773 Cluster Size Distribution in a Monte Carlo Simulation of the Micellar Phase of an Amphiphile and Solvent Mixture, 2905 Potassium 5-Hexenoate and Conformational Change on Micellization, 789 Vibrational Spectra of Potassium 4-Pentenoate and Microelectrodes The Study of Aluminium Deposition from Tetrahydrofuran Solutions of AlC1,-LiAlH, using Microelectrodes. Part 2.-The Influence of Solution Composition, 2795 Microemulsions Rotating Diffusion Cell Studies of Microemulsion The Kinetics of Solubilisate Exchange between Kinetics, 2407 Water Droplets of a Water-in-oil Microemulsion, 985 to a Macrofluid-like Water-in-oil Microemulsion, 162 1 and Critical Fluctuations in Water-in-oil Microemulsions, 1007 Self-consistency of the Percolation Model as applied Fluorescence Quenching as a Probe of Size Domains Microwave Spectroscopy Mechanism of Deuterium Addition and Exchange with Propene over Ni/SiO, and Pt/SiO, Catalysts at Low Temperatures, 2475xx SUBJECT INDEX Mixed Solvent Fluorescence of Ethidium in Alcohol-Water Solutions, 1609 Molar Conductivies Mobilities and Molar Volumes of Multicharged Cations in N,N-Dimethylformamide at 25 "C, 28 1 Molar Volume The Molar Volume of a Large Polymeric Cation W~304,,H4817+, 1725 Mobilities and Molar Volumes of Multicharged Cations in N,N-Dimethylformamide at 25 "C, 28 1 Molecular Crystals Potential-energy Calculations of the Mechanisms of Self-diffusion in Molecular Crystals.Part 2.-Naphthalene, 138 1 Molecular Sieves Smectite Molecular Sieves. Part 2.-Expanded Fluorhectorite Sorbents, 779 Molecular-orbital Calculations CH Bond Activation and Radical-Surface Reactions for Propylene and Methane over a-Bi,O,, 463 Molten Salts Intermolecular Structure around Lithium Monovalent Cations in Molten LiAICl,, 2925 Physicochemical Characterization of ZnO/Al,O, and Zn@MoO,/Al,O, Catalysts, 665 Cross-relaxation of Hydrogen Atoms adsorbed on a Molybdena-Silica Catalyst, 8 13 Adsorption of Thiophene and Model Hydrocarbons on MoO,/y-Al,O, Catalysts studied by Gas-Solid Chromatography, 1 179 The Nature of Supported-molybdena Catalysts. Evidence from a Raman and X-Ray Diffraction Investigation of Pyridine Adsorption, 160 1 Homologation Reaction on Molybdena-Silica Catalysts, 1859 Photoinduced Reactions of Methane with Molybdena Supported on Silica, 238 1 Study of the Influence of the Impregnation Acidity on the Structure and Properties of Molybdena-Silica Catalysts, 2835 Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids.Part 5.- Elucidation of Structures of Hydrated and of Dehydrated Heteropoly Acids by Quantum Chemical Calculations of Electron Spin Resonance Parameters, 1041 Hydrodesulphurisation Catalysts supported on Carbon and Alumina, 2145 Catalytic Activity and Structure of Mo Oxide Highly Dispersed on ZrO, for Oxidation Reactions, 1761 Molybdenum Reactive Intermediates for the Ethene The Role of Co in Sulphidised Co-Mo Monoethylene Aluminium(0) The Electron Spin Resonance Spectrum of Al[C,H,J in Hydrocarbon Matrices, 3701 Monte Carlo Simulation Cluster Size Distribution in a Monte Carlo Simulation of the Micellar Phase of an Amphiphile and Solvent Mixture, 2905 Montmorillonite Metachromasy in Clay Minerals.Sorption of Pyronin Y by Montmorillonite and Laponite, 1685 Synthesis of Montmorillonite-Viologen Intercalation Compounds and their Photochromic Behaviour, 1851 Morphotinium Electron Nuclear Double Resonance of S = 1/2 Defects in a Single Crystal of the Morpholinium-TCNQ 1 : 1 Complex, 57 Mhbauer Spectroscopy An In Situ Mossbauer Spectroscopic Investigation of Titania-supported Iron-Ruthenium Catalysts, 2573 Nafion Binding of Paramagnetic Ions in Ionomers.Cu2+ and Ti3+ in Nafion Membranes, 3575 Naphthalene Potential-energy Calculations of the Mechanisms of Self-diffusion in Molecular Crystals. Part 2.-Naphthalene, 138 1 1,QNaphthoquinone Linewidth Alternation, as a Result of Intramolecular Cation Migration, in the Electron Spin Resonance Spectrum of the 1,4- Naphthoquinone Radical Anion, 167 Neopentane Reaction of Neopentane with Hydrogen over Pd, Pt, Ir and Rh, 1293 Neutron Diffraction Intermolecular Structure around Lithium Monovalent Cations in Molten LiAlCl,, 2925 Neutron Spectroscopic Study of Polycrystalline Benzene and of Benzene adsorbed in Na-Y Zeolite, 3 199 A Neutron Scattering Study, 687 Absence of Fast H'-ion Motion in Aqueous HCl.Nickel Kinetics of Metal Oxide Dissolution. Oxidative Dissolution of Chromium from Mixed Nickel-Iron-Chromium Oxides by Permanganate, 37 1 Influence of Lithium on Reduction, Dispersion and Hydrogenation Activity of Nickel on Alumina Catalysts, 733 Experimental Evaluation of Adsorption Behaviour of Intermediates in Anodic Oxygen Evolution at Oxidized Nickel Surfaces, 1063 Interactions between Carbon Monoxide and Coadsorbed Promoters on Nickel Surfaces, 1945 Mechanism of Deuterium Addition and Exchange with Propene over Ni/SiO, and Pt/SiO, Catalysts at Low Temperatures, 2475 Kinetics of Inhibition Reactions in the Hydrogenolysis of C,H, on a Nickel Wire Catalyst, 2825 Local Structure of Nickel Oxide grown at High Temperatures in Ceramic Electrolyte Cells, 289 Adsorptive Properties of Semiconducting Thin NiO and TiO, Films combined with an Oppositely Polarized Ferroelectric Support, 306 1 Catalytic Implications of Local Electronic Kinetic Modelling of Multiple-site Activity and theSUBJECT INDEX xxi Nickel (cont.) Control of Ni Metal Particle Size in Ni/SiO, Catalysts by Calcination and Reduction Temperatures, 3 189 Nitrogen Infrared Studies on Dinitrogen and Dihydrogen adsorbed over TiO, at Low Temperatures, 2765 Nitroimidazole Polarographic Evidence for the Interaction of Reduced Nitroimidazole Derivatives with DNA Bases, 257 Nitrous Oxide Kinetics of N,O Decomposition on the Surface of Oxidative Coupling of Methane over Samarium Kinetics and Mechanism of Oxidative y-Al,O, doped with Sodium Ions, 627 Oxides Using N,O as the Oxidant, 13 15 Dehydrogenation of Ethane and Small Alkanes with Nitrous Oxide over Cobalt-doped Magnesium Oxide, 3 139 Nitroxide An Electron Nuclear Double Resonance Study in a Glassy Matrix of Nitroxide Radicals with Delocalized Spin Density, 69 Use of Nitroxides to Measure Redox Metabolism in Cells and Tissues, 191 N,N-Dimeth y lformamide Mobilities and Molar Volumes of Multicharged Cations in N,N-Dimethylformamide at 25 "C, 28 1 Nuclear Magnetic Resonance Hydrogen- 1 Nuclear Magnetic Resonance, Differential Thermal Analysis, X-Ray Powder Diffraction and Electrical Conductivity Studies on the Motion of Cations, including Self- diffusion in Crystals of Propylammonium Chloride and Bromide as well as their N- Deuterated Analogues, 3207 in Cells and Tissues, 191 Xenon adsorbed on Zeolite NaY exchanged with Alkali-metal and Alkaline-earth Cations, 45 1 A 'H and 13C Nuclear Magnetic Resonance Study of the Conformation of Aerosol OT in Water and Hydrocarbon Solutions, 5 17 Nuclear Magnetic Resonance Study of the Reaction of the Tetrahydroxyborate Ion with Two Chiral I,3-Diols, 771 Phosphorus-3 1 Nuclear Magnetic Resonance Studies of Solid Diphosphine Disulphides.Crystallographic Considerations, 1055 Identification of the Structural Transition Temperature in the Solutions of Dialkyl Sulphoxides, 1 189 'H and 13C Nuclear Magnetic Relaxation Studies of the Cubic Liquid-crystalline Phase I, in the Sodium Octanoateactane-Water System, 151 5 Selective 'H-I3C and 'H-'H Nuclear Overhauser Enhancement Studies of Adenosine-Thymidine Interaction in Solution, 173 1 Origin of Boron Mobility over Boron-impregnated ZSM-5.A Combined High-resolution-Solid- Use of Nitroxides to Measure Redox Metabolism '*'Xe Nuclear Magnetic Resonance Study of A Polarimetric, Circular Dichroism and "B state "B Nuclear Magnetic Resonance/Infrared Spectral Investigation, 175 I Nuclear Magnetic Resonance Self-diffusion Studies of Methanol-Water Mixtures in Pentasil-type Zeolites, 1843 ZSM-5 containing Co-adsorbed Benzene, and the Location of the Benzene Molecules, 2301 Hexaoxaoctadecanesodium( I) Cation ("a. i K 6 ] +) in Several Solvents. A Sodium-23 Nuclear Magnetic Resonance Study, 2459 Constants of Pyrene with 2,4,6-Trinitrotoluene in Solution determined by 'H-Nuclear Magnetic Resonance from Non-linear Scatchard Plots, 2641 Cyclodextrins.A 19F Nuclear Magnetic Resonance and Spectrophotometric Study, 2697 Ion-pair Formation by Tetra-alkylammonium Ions in Methanol. A Nuclear Magnetic Resonance Study, 3419 Resonance, Nuclear Magnetic Resonance and Optical Transitions: More than Just a Game?, 3469 Molecular Mobility of Methane adsorbed on Sodium Ion Exchange on the 1,4,7,10,13,16- Electron-donor-Electron-acceptor Association The Inclusion of Diflunisal by a- and j3- Multiple Resonances involving Electron Spin Nuclear Overhauser Enhancement Selective 'H-13C and 'H-'H Nuclear Overhauser Enhancement Studies of Adenosine-Thymidine Interaction in Solution, 1731 Magnetic Relaxation in Micellar and Non- micellar Sodium Octanoate, 2593 Coupled 13C Longitudinal and Transverse Nuclear Quadruple Resonance 35Cl Nuclear Quadrupole Resonance and Infrared Spectroscopic Studies of Hydrogen Bonding in Complexes of Trichloroacetic Acid with Various Nitrogen and Oxygen Bases, 2541 Optical Transitions Multiple Resonances involving Electron Spin Resonance, Nuclear Magnetic Resonance and Optical Transitions: More than Just a Game?, 3469 Oscillatory Phenomena Influence of Mixed Cerium(1v) Sulphate and Ferroin Catalysts on the Oscillatory Redox Reaction between Malonic Acid and Bromate, 267 Osmotic Coefficients Non-ideal Behaviour of Benzene Solutions of Tri- n-octylammonium Bromide and Cyclohexanol, 231 1 Oxac ycloalkanes The Mechanism of Hydrogenolysis and Isomerization of Oxacycloalkanes on Metals.Part 8.-New Results on the Mechanism of Hydrogenolysis of Oxiranes on Platinum and Palladium, 2359 Oxidative Dehydrogenation Kinetics and Mechanism of Oxidative Dehydrogenation of Ethane and Small Alkanes with Nitrous Oxide over Cobalt-doped Magnesium Oxide, 3 139xxii SUBJECT INDEX Oxovanadium Oxovanadium(1v) Complexes of Cysteine characterized by Electron Spin Resonance Spectroscopy, 3627 Oxygen Experimental Evaluation of Adsorption Behaviour of Intermediates in Anodic Oxygen Evolution at Oxidized Nickel Surfaces, 1063 naphthoquinones immobilized at Carbon Electrodes, 1823 A Dye-sensitized Photocatalyst @-Type CuCNS) for the Generation of Ocygen from Aqueous Persulphate, 2553 Oxygen Diffusion-Concentration in Phospholipidic Model Membranes.An Electron Spin Resonance-Saturation Study, 177 Mechanism of Oxygen Reactions at Porous Oxide Electrodes. Part 1 .--Oxygen Evolution at RuO, and Ru, Sn,-, 0, Electrodes in Alkaline Solution under Vigorous Electrolysis Conditions, 299 the Influence of Hydrogen on the Oxygen-Silver Interaction, 3 16 1 Oxygen Reduction with Hydroxy- 1,4- An X-Ray Photoelectron Spectroscopy Study of Palladium Reaction of Neopentane with Hydrogen over Pd, Chemisorption and Disproportionation of Carbon Pt, Ir and Rh, 1293 Monoxide on Palladium/Silica Catalysts of differing Percentage Metal Exposed, 2757 Emulsion Polymerization of Butyl Acrylate. Kinetics of Particle Growth, 1449 Control of Ni Metal Particle Size in Ni/SiO, Catalysts by Calcination and Reduction Temperatures, 3 189 Particle Growth Pentanol Surface Potential Measurements in Pentanol-Sodium Dodecyl Sulphate Micelles, 59 1 Percolation Model Self-consistency of the Percolation Model as applied to a Macrofluid-like Water-in-Oil Microemulsion, 1621 Persulphate A Dye-sensitized Photocatalyst @-Type CuCNS) for the Generation of Ocygen from Aqueous Persulphate, 2553 Phase Transition The Liquid-Vapour Transition in Monolayers of n-Pentadecanoic Acid at the Air/Water Interface, 585 Phenol Calorimetric Investigations of Association in Ternary Systems.Part 4.-The Influence of Solvation on Enthalpy of Complex Formation in Phenol-Tetrahydrofuran and 2,6- Dimethylphenol-Tetrahydrofuran Systems, 3083 Kinetics of Hydrolysis of Phenyl Dichloroacetates Phenyl Dichloroacetates in Aqueous Salt Solutions, 865 pPhen y lewdiamine Comparison between Heterogeneous and Homogeneous Electron Transfer in p - Phenylenediamine Systems, 2727 Phenyl-N-t-butylnitrone Nature of Radical Reactivity of Organic Plasma- exposed Glass Surface studied by the Electron Spin Resonance Spin-trapping Technique, 1579 Phosphate Spectromagnetic Evidence for Spatial Correlation of Copper Centres in Phosphate Glasses and its Effect on the Charge-transport Processes, 3587 Part 2.-Phosphates with Amines, 1885 Electrostatic Interactions between Organic Ions.Phospholipids Oxygen Diffusion-Concentration in Phospholipidic Model Membranes. An Electron Spin Resonance-Saturation Study, 177 Diheptylsulphosuccinate Dihydrate and Comparison with Phospholipids, 3093 The Crystal Structure of Sodium Phosphorus Radical Cations of Trialkylphosphine Oxides, Trialkylphosphates, Hexamethylphosphoramide, Dimethyl Sulphoxide and various Sulphones, Sulphites and Sulphates.An Electron Spin Resonance and Radiation Chemical Study, 383 Radiation Damage in a Phosphated Sugar. An Electron Spin Resonance Study of Phosphorus- centred Radicals Trapped in an X-Irradiated Single Crystal of a Phenoxyphosphoryl Xylofuranose Derivative, 40 1 Paramagnetic Adducts in the Reaction of 4- Substituted Pyridines and Phosphorus-centred Radicals, 91 Photoallergens An Electron Spin Resonance Study of the Radicals formed on Ultraviolet Irradiation of the Photoallergens Fentichlor and Bithionol, 135 Investigation of the Mechanism of Photocatalytic Alcohol Dehydrogenation over Pt/TiO, using Poisons and Labelled Ethanol, 697 Photogeneration of Hydrogen from Water over an Alumina-supported ZnS-CdS Catalyst, 1395 Photocatalytic Dehydrogenation of Liquid Alcohols by Platinized Anatase, 1631 A Dye-sensitized Photocatalyst @-Type CuCNS) for the Generation of Ocygen from Aqueous Persulphate, 2553 The Two-electron Oxidation of Methyl Viologen. Detection and Analysis of Two Fluorescing Products, 2559 Light-induced Hydrogen Formation and Photo- uptake of Oxygen in Colloidal Suspensions of a- Fe,O,, 1101 Photochemical Formation of Colloidal Metals, 1559 Synthesis of Montmorillonite-Viologen Intercalation Compounds and their Photochromic Behaviour, 185 1 Methyl Orange as a Probe of the Semiconductor-Electrolyte Interfaces in CdS Suspensions, 2647 Polymerization Photoinitiators based on the Acetophenone Nucleus, 2935 Photochemistry Excited-state Reactivity in a Series ofSUBJECT INDEX xxiii Photochemistry (cont.) Metal-organic Chemical Vapour Deposition (MOCVD) of Compound Semiconductors.Part 2.-Preparation of ZnSe Epitaxial Layers on (1 00) Oriented GaAs Single-crystalline Substrates, 323 Photoelectron Spectroscopy The Promotion of Surface-catalysed Reactions by Gaseous Additives. The Role of a Surface Oxygen Transient, 2047 Photo1 ysis Reactions of Alkylperoxyl Radicals in Solution. Part 2.-A Kinetic and Product Study of Self- reactions of 2-Propylperoxyl Radicals between 253 and 323 K, 2433 Photosynthesis Magnetic Resonance of Ultrafast Chemical Reactions. Examples from Photosynthesis, 13 Studies of the Manganese Site of Photosystem I1 by Electron Spin Resonance Spectroscopy, 3635 Picric Acid The Ethane- 1,2-diol-2-Methoxyethanol Solvent System.The Dependence of the Dissociation Constant of Picric Acid on the Temperature and Compositon of the Solvent Mixture, 3 129 Plasma-exposed Glass Nature of Radical Reactivity of Organic Plasma- exposed Glass Surface studied by the Electron Spin Resonance Spin-trapping Technique, 1579 Reaction of Neopentane with Hydrogen over Pd, Pt, Ir and Rh, 1293 Aspects of Temperature-programmed Analysis of some Gas-Solid Reactions. Part 2.-Hydrogen Temperature-programmed Desorption from Silica-supported Platinum, 1369 Isothermal Titration of Supported Platinum. Part 1 . 4 0 - 0 , Titration, 1651 Isothermal Titration of Supported Platinum.Part 2.-Alkene Titration using Cyclohexene, 1667 Comparison of Hydrogenation and Hydrogenolysis on Unsupported and Silica- supported Rh-V,O, and Pt-V,O,, 209 1 Promotion of Platinum-based Catalysts for Methanol Synthesis from Syngas, 2 1 13 Mechanism of Deuterium Addition and Exchange with Propene over Ni/SiO, and Pt/SiO, Catalysts at Low Temperatures, 2475 of Measuring Adsorption at the Gas-Solid Interface, 2693 Electron Spin Resonance Studies of HPt(CN)t- and Pt(CN)i- formed by Irradiation of K, Pt(CN), in Solvents, 2803 Oxidation of 2,4-Dibromo-6-nitroaniline in Aqueous Sulphuric Acid Solutions on a Platinum Electrode, 2619 Platinum A New Pressure-programmed Volumetric Method Poisoning Investigation of the Mechanism of Photocatalytic Alcohol Dehydrogenation over Pt/TiO, using Poisons and Labelled Ethanol, 697 Polarimetr y A Polarimetric, Circular Dichroism and "B Nuclear Magnetic Resonance Study of the Reaction of the Tetrahydroxyborate Ion with Two Chiral 1,3-Diols, 771 Polarity Local Polarity of Solvent Mixtures in the Field of Electronically Excited Molecules and Exciplexes, 495 Polarogr aph y Polarographic Evidence for the Interaction of Reduced Nitroimidazole Derivatives with DNA Bases, 257 Medium Effect on the Electrochemical Behaviour of the Cd"/Cd (Hg) System in Propane- 1,2- diol-Water Mixtures, 28 13 Polymers Dynamic Properties and Structure of Salt-free Polystyrene Sulphonate Solutions, 801 Thermodynamic Properties of Concentrated Heteroionic Polyelectrolyte Solutions, 3249 Acrylonitrile Polymerization from Aqueous Solution.The Role of Surfactants, 645 Acrylonitrile Polymerization from Aqueous Solution. The Role of Particle Area, 657 Emulsion Polymerization of Butyl Acrylate. Kinetics of Particle Growth, 1449 Excited-state Reactivity in a Series of Polymerization Photoinitiators based on the Acetophenone Nucleus, 2935 Towards a Complete Configurational Theory of Non-equilibrium Polymer Adsorption, 25 15 The Mechanism of Conductivity of Liquid Polymer Electrolytes, 3345 Kinetics of Pyrrole Polymerisation in Aqueous Iron Chloride Solution, 1507 Thermodynamic Properties of the PMMA-Acetoni trile- I ,4- Dioxane System, 2289 Kinetic and Equilibrium Studies associated with the Aggregation of Non-ionic Surfactants in Non-polar Solvents, 2735 Time-resolved Reflection Spectrum of Ordered Structure of Monodispersed Polystyrene Spheres in an Electric Field, 2487 Effect of Neutral Polymers on the Ordering of Monodispersed Polystyrene Spheres, 2497 Transport Phenomena in Concentrated Aqueous Solutions of Sodium-Caesium Polystyrene Sulphonates, 3259 Interactions of Acetic Acid with Some Polyvinylpyridines in Aqueous Solution, 2525 Ultrasonic Relaxation Studies associated with the Pores One-dimensional Rare Gases in the Pores of Ferrierite and their Virial Coefficients, 33 17 Hydrogenation of CO, over Co/Cu/K Catalysts, Chemical and Electrostatic Interactions between Potassium 171 1 Alkali Metals and Carbon Monoxide on Metal Single-crystal Surfaces, 200 1 The Promoting Role of Cr and K in Catalysts from High-pressure and High-temperature Methanol and Higher-alcohol Synthesis, 2213xxiv SUBJECT INDEX Potassium (cont.) Standard Gibbs Free Energies of Transfer of NaCl and KCl from Water to Mixtures of the Four Isomers of Butyl Alcohol with Water.The Use of Ion-selective Electrodes to Study the Thermodynamics of Solutions, 635 Crystals, 3709 Anions, 21 1 Potassium 5-Hexenoate and Conformational Change on Micellization, 789 N; and (CN); Spin-Lattice Relaxation in KCN Reactions of Ozonate and Superoxide Radical Vibrational Spectra of Potassium 4-Pentenoate and Potential-energy Calculations Potential-energy Calculations of the Mechanisms of Self-diffusion in Molecular Crystals. Part 2.-Naphthalene, 138 1 Potentiometr y Estimations of Stability Constants by Potentiometry of some Lanthanum and Erbium Dicarboxylates at Constant Ionic Strength, 425 Effect of Diphosphonates on the Precipitation of Precipitation Calcium Carbonate in Aqueous Solutions, 1477 Promotion Hydrogenation of CO, over Co/Cu/K Catalysts, 171 1 Catalytic Activity and Structure of Mo Oxide Highly Dispersed on ZrO, for Oxidation Reactions, 176 1 and Prospect, 1893 metal Surfaces, 19 15 Coadsorption Phenomena, 1935 Interactions between Carbon Monoxide and Coadsorbed Promoters on Nickel Surfaces, 1945 Overlayers. Cu/Ru(0001), 1967 Surface Reactivity of Ru(0001), 1975 Alkali Metals and Carbon Monoxide on Metal Single-crystal Surfaces, 200 1 Adsorption and Dissociation of CO, on a Potassium-promoted Rh( 1 1 1) Surface, 20 15 Alkali Metal, Chlorine and other Promoters in the Silver-catalysed Selective Oxidation of Ethylene, 2035 The Promotion of Surface-catalysed Reactions by Gaseous Additives. The Role of a Surface Oxygen Transient, 2047 The Effects of Titania and Alumina Overlayers on the Hydrogenation of CO over Rhodium, 2061 Comparison of Hydrogenation and Hydrogenolysis on Unsupported and Silica- supported Rh-V,O, and R-V,O,, 209 1 Manipulation of the Selectivity of Rhodium by the Use of Supports and Promoters, 2103 Promotion of Platinum-based Catalysts for Methanol Synthesis from Syngas, 21 13 Promotion in Heterogeneous Catalysis: Retrospect Coordination of Carbon Monoxide to Transition- Electrostatic Interactions and their Role in Catalytic Implications of Local Electronic Adsorption and Reaction on Strained-metal A Comparison of the Effects of Cu and Au on the Chemical and Electrostatic Interactions between Ethanol Promotion by the Addition of Cerium to The Role of Co in Sulphidised Co-Mo Rhodium-Silica Catalysts, 2 1 19 Hydrodesulphurisation Catalysts supported on Carbon and Alumina, 2145 Inorganic Cluster Compounds as Models for the Structure of Active Sites in Promoted Hydrodesulphurisation Catalysts, 2 157 Chemisorption and Ammonia Synthesis on Alumina-supported Hexagonal Tungsten Bronze, K, WO,, 2175 Promotion of Methanol Synthesis and the Water- gas Shift Reactions by Adsorbed Oxygen on Supported Copper Catalysts, 2193 The Promoting Role of Cr and K in Catalysts from High-pressure and High-temperature Methanol and Higher-alcohol Synthesis, 2213 Propan-2-01 Adsorption and Decomposition on Zinc Oxide promoted by Alkali Metal, 2227 A Kinetic Study of the Self-reaction of Prop-2- Promotion of Nitrogen and Hydrogen Prop-2-ylperoxyl Radicals ylperoxyl Radicals in Solution using Ultraviolet Absorption Spectroscopy, 1805 Propan-2-01 The Use of Hydride-forming Rare-earth-Cobalt Intermetallic Compounds in the Dehydrogenation of Propan-2-01, 743 Propan-2-01 Adsorption and Decomposition on Zinc Oxide promoted by Alkali Metal, 2227 Medium Effect on the Electrochemical Behaviour of the Cd"/Cd (Hg) System in Propane- 1,2- diol-Water Mixtures, 28 13 Propane-l,2diol Propylammonium Bromide Hydrogen- 1 Nuclear Magnetic Resonance, Differential Thermal Analysis, X-Ray Powder Diffraction and Electrical Conductivity Studies on the Motion of Cations, including Self- diffusion in Crystals of Propylammonium Chloride and Bromide as well as their N- Deuterated Analogues, 3207 Propylammonium Chloride Hydrogen- 1 Nuclear Magnetic Resonance, Differential Thermal Analysis, X-Ray Powder Diffraction and Electrical Conductivity Studies on the Motion of Cations, including Self- diffusion in Crystals of Propylammonium Chloride and Bromide as well as their N- Deuterated Analogues, 3207 Proteins A Vibronic Coupling Approach for the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins, 3693 Ultrasonic Relaxation Studies associated with the Proton Transfer Interactions of Acetic Acid with Some Polyvinylpyridines in Aqueous Solution, 2525 A Study of Proton Transfer by 2,2'-Bipyridine from Water to Nitrobenzene using Chronopotentiometry with Cyclic Linear Current-scanning and Cyclic Voltammetry, 2993SUBJECT INDEX xxv Russian Blue Site-transfer Conductivity in Solid Iron Hexacyanoferrates by Dielectric Relaxometry, Voltammetry and Spectroscopy.Prussian Blue, Congeners and Mixtures, 23 I Pulse Radiolysis One-electron Reduction of 2,2’-Bipyrimidine in Aqueous Solution, 341 5 Addition-Elimination Paths in Electron-transfer Reactions between Radicals and Molecules. Oxidation of Organic Molecules by the OH Radical, 113 Corrosion Processes in Quantized Semiconductor Colloids studied by Pulse Radiolysis, 1127 Electron-transfer Reactions on CdSe Colloids as studied by Pulse Radiolysis, 1193 Pulse Radiolysis Study of Salt Effects on Reactions of Aromatic Radical Cations with C1- .Rate Constants in the Absence and Presence of Quaternary Ammonium Salts, 1795 Primary Processes of Stabilizer Action in Radiation-induced Alkane Oxidation, 2365 Radical Spectra and Product Distribution following Electrophilic Attack by the OH’ Radical on 4-Hydroxybenzoic Acid and Subsequent Oxidation, 3177 Pyrene Electron-donor-Electron-acceptor Association Constants of Pyrene with 2,4,6-Trinitrotoluene in Solution determined by ’H-Nuclear Magnetic Resonance from Non-linear Scatchard Plots, 264 I Pyridine The Nature of Supported-molybdena Catalysts. Evidence from a Raman and X-Ray Diffraction Investigation of Pyridine Adsorption, 1601 Paramagnetic Adducts in the Reaction of 4- Substituted Pyridines and Phosphorus-centred Radicals, 91 Pyridoxine Hydrochloride A Single-crystal ENDOR Study of y-Irradiated Pyridoxine Hydrochloride, 37 Pyrimidines 35Cl Nuclear Quadrupole Resonance and Infrared Spectroscopic Studies of Hydrogen Bonding in Complexes of Trichloroacetic Acid with Various Nitrogen and Oxygen Bases, 2541 Pyronine The Inclusion of Pyronine Y by p- and y- Cyclodextrin. A Kinetic and Equilibrium Study, 3237 Pyrrole Kinetics of Pyrrole Polymerisation in Aqueous Iron Chloride Solution, 1507 Quantum Chemistry Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids.Part 5.- Elucidation of Structures of Hydrated and of Dehydrated Heteropoly Acids by Quantum Chemical Calculations of Electron Spin Resonance Parameters, 104 1 Quaternary Systems A New Analytical Solution of the Quaternary Gibbs-Duhem Equation, 3367 QuillOIU? Radical Spectra and Product Distribution following Electrophilic Attack by the OH’ Radical on 4-Hydroxybenzoic Acid and Subsequent Oxidation, 3 177 Radiation Chemistry Application of Electron Spin Resonance Spectroscopy to the Study of the Effects of ionizing Radiation on DNA and DNA Complexes, 1 Electron Spin Resonance Studies of HPt(CN)i- and Pt(CN)i- formed by irradiation of K, Pt(CN), in Solvents, 2803 Radical Cations of Trialkylphosphine Oxides, Trialkylphosphates, Hexamethylphosphoramide, Dimethyl Sulphoxide and various Sulphona, Sulphites and Sulphates.An Eiectron Spin Resonance and Radiation Chemical Study, 383 Radiation Damage in a Phosphated Sugar. An Electron Spin Resonance Study of Phosphorus- centred Radicals Trapped in an X-Irradiated Single Crystal of a Phenoxyphosphoryl Xylofuranose Derivative, 401 An Electron Spin Resonance Study of Triplet Radical Pairs in Single Crystals of X-Irradiated L-Ascorbic Acid at 77 K, 1869 Magnesium Oxide, 3 107 ‘ Doping Effect of Sodium on y-Irradiated Radiographic Films Kinetic Models for the Development of Density in Radiographic Film.Visible-light Exposure, 2953 Radio1 ysis Application of Electron Spin Resonance Spectroscopy to the Study of the Effects of Ionizing Radiation on DNA and DNA Complexes, 1 A Single-crystal ENDOR Study of y-Irradiated Pyridoxine Hydrochloride, 37 Radical Production evidenced by Dimer Analysis in y-Irradiated Amides in Aqueous Solutions and in the Solid State, 125 Spin-trapping Study of the Radiolysis of CCI,, 219 High-performance Liquid Chromatography-Electron Spin Resonance Analysis of Sugars irradiated in the Solid and Liquid Phase, 225 The Two-electron Oxidation of Methyl Viologen.Detection and Analysis of Two Fluorescing Products, 2559 Single-crystal Electron Spin Resonance Studies in Radiation-produced Species in Ice I,. Part 1.-The 0- Radicals, 3725 Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals, 3737 Single-crystal Electron Spin Resonance Studies on Radiotracer Study Radiotracer Studies of Chemisorption on Copper- based Catalysts. Part 1 .-The Adsorption of Carbon Monoxide and Carbon Dioxide on Copper/Zinc Oxide/Alumina and Related Catalysts, 3399 Raman Spectroscopy Vibrational Spectra of Potassium CPentenoate and Potassium 5-Hexenoate and Conformational Change on Micellization, 789xxvi SUBJECT INDEX Raman Spectroscopy (cont.) The Nature of Supported-molybdena Catalysts.Evidence from a Raman and X-Ray Diffraction Investigation of Pyridine Adsorption, 1601 The Use of Hydride-forming Rare-earth-Cobalt Rare Earth Metal Intermetallic Compounds in the Dehydrogenation of Propan-2-01, 743 Rare Gas One-dimensional Rare Gases in the Pores of Ferrierite and their Virial Coefficients, 33 17 Use of Nitroxides to Measure Redox Metabolism in Cells and Tissues, 191 Redox Reactions with Colloidal Metal Oxides. Comparison of Radiation-generated and Chemically-generated RuO, .2H,O and MnO, Colloids, 3001 Redox Reaction Reduced Potential Curves Ground-state Reduced Potential Curves (RPC) of Non-metallic First- and Second-row Hydrides, 2857 Reduction Non-isothermal Reduction Kinetics and Reducibilities of Nickel and Cobalt Faujasites, 3015 Control of Ni Metal Particle Size in Ni/SiO, Catalysts by Calcination and Reduction Temperatures, 3 189 Aqueous Solution, 34 15 One-electron Reduction of 2,Y-Bipyrimidine in Refractive Index Refractive Index and Excess Volume for Binary Liquid Mixtures.Part 1 .-Analyses of New and Old Data for Binary Mixtures, 2449 Benzene, Toluene, p-Xylene, Quinoline and Cyclohexane. Part 3.-Dielectric Properties and Refractive Indices at 308.15 K, 3167 Binary Systems of 1 ,ZDichloroethane with Rhenium Influence of Metal-Support Interactions on the Hydrogenolysis of Methylcyclopentane over Supported Rh Catalysts, 9 13 ReIV in TiO,, 3613 The Electron Spin Resonance Powder Spectrum of Rhodium Reaction of Neopentane with Hydrogen over Pd, The Effect of Hydrogen Sulphide on the Pt, Ir and Rh, 1293 Adsorption and Thermal Desorption of Carbon Monoxide over Rhodium Catalysts, 1835 Adsorption and Dissociation of CO, on a Potassium-promoted Rh( 1 11) Surface, 201 5 The Effects of Titania and Alumina Overlayers on the Hydrogenation of CO over Rhodium, 2061 Comparison of Hydrogenation and Hydrogenolysis on Unsupported and Silica- supported Rh-V,O, and F't-V,O,, 209 1 Use of Supports and Promoters, 2103 Process of Preparation of Rhodium/Lanthana Catalysts, 2279 Characterization of CO-Rh species formed on Rh- Y Zeolite by Temperature-programmed Desorption and Infrared Techniques, 2605 Manipulation of the Selectivity of Rhodium by the Study of the Support Evolution through the Ethanol Promotion by the Addition of Cerium to Rhodium-Silica Catalysts, 21 19 Ri fam ycins Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution.Part 2.-Rifamycins, 3675 Rotating Diffusion Cell Kinetics, 2407 Rotating-disc Electrode Rotating Diffusion Cell Studies of Microemulsion Oxidation of 2,4-Dibromo-6-nitroaniline in Aqueous Sulphuric Acid Solutions on a Platinum Electrode, 2619 Rotating-disc Electrodes. ECE and DISPl Processes, 1261 Rubidium Structure of Second-stage Graphite-Rubidium, C,,Rb, 3447 Ruthenium Optical and Spectromagnetical Properties of Phosphate Glasses containing Ruthenium and Titanium Ions, 705 Chemisorption and Catalysis by Metal Clusters.Hydrogenation of Carbon Monoxide and Carbon Dioxide catalysed by Supported Ruthenium Clusters derived from Ru,(CO),, and from H,Ru,(CO),,, 905 Infrared Spectroscopic Study of Catalytic Activity of Rh/TiO, for the CO+H, Reaction, 1427 Oxygen Evolution by Water Oxidation with Polynuclear Ruthenium Complexes, 1539 Adsorption and Reaction on Strained-metal Overlayers. Cu/Ru(0001), 1967 A Comparison of the Effects of Cu and Au on the Surface Reactivity of Ru(0001), 1975 Electron Spin Resonance Investigations of Ruthenium supported on y-Alumina, 2271 An In Situ Mossbauer Spectroscopic Investigation of Titania-supported Iron-Ruthenium Catalysts, 2573 Interaction of Carbon Monoxide with Ru/yAl,O,. An Electron Spin Resonance Investigation, 3619 Mechanism of Oxygen Reactions at Porous Oxide Electrodes.Part 1 .--Oxygen Evolution at RuO, and Ru, Sn,-, 0, Electrodes in Alkaline Solution under Vigorous Electrolysis Conditions, 299 Thermally Activated Ruthenium Dioxide Hydrate. A Reproducible, Stable Oxygen Catalyst, 233 1 Corrosion of Ruthenium Dioxide Hydrate by Ce'" Ions and other Oxidants, 2317 Samarium Oxidative Coupling of Methane over Samarium Oxides Using N,O as the Oxidant, 13 15 Saturation Transfer Electron Spin Resonance Electron Spin Resonance and Saturation Transfer Electron Spin Resonance of Virus and Membrane Systems, 203 Scanning Transmission Electron Microscopy A Study of the Adsorption Sites on Thoria by Scanning Transmission Electron Microscopyand Fourier-transform Infrared Spectroscopy. Adsorption and Desorption of Water and Methanol, 1417SUBJECT INDEX xxvii Scatchard Plots Electron-donor-Electron-acceptor Association Constants of Pyrene with 2,4,6-Trinitrotoluene in Solution determined by 'H-Nuclear Magnetic Resonance from Non-linear Scatchard Plots, 2641 Sedimentation The Consolidation of Concentrated Suspensions.Part 1 .-The Theory of Sedimentation, 873 Selectivity Manipulation of the Selectivity of Rhodium by the Use of Supports and Promoters, 2103 Self-diffusion Potential-energy Calculations of the Mechanisms of Self-diffusion in Molecular Crystals. Part 2.-Naphthalene, 138 1 Nuclear Magnetic Resonance Self-diffusion Studies of Methanol-Water Mixtures in Pentad-type Zeolites, 1843 Self-exchange Reactions The Role of Solvent Reorganization Dynamics in Homogeneous Electron Self-exchange Reactions, 161 Self-reaction A Kinetic Study of the Self-reaction of Prop-2- ylperoxyl Radicals in Solution using Ultraviolet Absorption Spectroscopy, 1805 Semiconductor Corrosion Processes in Quantized Semiconductor Colloids studied by Pulse Radiolysis, 1127 Photogeneration of Hydrogen from Water over an Alumina-supported ZnS-CdS Catalyst, 1395 Metal-organic Chemical Vapour Deposition (MOCVD) of Compound Semiconductors.Part 2.-Preparation of ZnSe Epitaxial Layers on (100) Oriented GaAs Single-crystalline Substrates, 323 Semiconductor-Electrolyte Interfaces in CdS Suspensions, 2647 Adsorptive Properties of Semiconducting Thin NiO and TiO, Films combined with an Oppositely Polarized Ferroelectric Support, 306 1 Setschenow Coefficients for Caffeine, Theophylline Methyl Orange as a Probe of the Setschenow Coefficients and Theobromine in Aqueous Electrolyte Solutions, 1029 Silica Cross-relaxation of Hydrogen Atoms adsorbed on Structure of the Catalytic Site on the Silica- a Molybdena-Silica Catalyst, 8 13 supported Catalyst derived from Copper(r1) Acetate, 1227 Homologation Reaction on Molybdena-Silica Catalysts, 1859 Photoinduced Reactions of Methane with Molybdena Supported on Silica, 238 1 Extended X-Ray Absorption Fine Structure Study of the Reaction between Silica-supported Copper(I1) Oxide Catalysts and Acetic Acid, 2635 Monoxide on Palladium/Silica Catalysts of differing Percentage Metal Exposed, 2757 Reactive Intermediates for the Ethene Chemisorption and Disproportionation of Carbon Infrared Study of the Adsorption of Non-ionic Infrared Study of the Desorption of Surfactants on Silica, 3283 Polycondensed Aromatic Compounds by Non- ionic Surfactants at the Silica-Carbon Tetrachloride Interface, 3295 Properties of Capillary-condensed Benzene, 1203 Hemimicelle Formation of Cationic Surfactants at Silica Gel-Water Interface, 267 1 Silver Photochemical Formation of Colloidal Metals, 1559 Alkali Metal, Chlorine and other Promoters in the Silver-catalysed Selective Oxidation of Ethylene, 2035 Supported 12-Heteropoly Acids.Part 6.-The Investigation of Reduced H,(SiW,,O,,)~ x H,O and Ag,(SiW,,O,,)~x H,O and the Effects of Oxygen Adsorption, 3 1 15 Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalcogenides, 3527 Fluorescence Quenching as a Probe of Size Electron Spin Resonance Studies of Free and Size Domain Domains and Critical Fluctuations in Water-in- oil Microemulsions, 1007 Small-angle Neutron Scattering A Small-angle Neutron Scattering Investigation of Rod-like Micelles aligned by Shear Flow, 2773 Smectite Smectite Molecular Sieves.Part 2.-Expanded Fluorhectorite Sorbents, 779 Sodium Chloride Standard Gibbs Free Energies of Transfer of NaCl and KC1 from Water to Mixtures of the Four Isomers of Butyl Alcohol with Water. The Use of Ion-selective Electrodes to Study the Thermodynamics of Solutions, 635 Sodium Dodecyl Sulphate Surface Potential Measurements in Pentanol-Sodium Dodecyl Sulphate Micelles, 59 1 Micellar Effects upon the Reactions of Complex Ions in Solution.Retardation of the Base Hydrolysis of cis- (Azido)(imidazole)bis(ethylenediamine)cobalt( 111) by Sodium Dodecyl Sulphate, 1307 Oil-Water-Surfactant Systems. Effects of Cosurfactant in Systems containing Sodium Dodecyl Sulphate, 2347 Interfacial Tension Minima in Sodium Octanoate *H and 13C Nuclear Magnetic Relaxation Studies of the Cubic Liquid-crystalline Phase I, in the Sodium Octanoate4ctane-Water System, 1515 Magnetic Relaxation in Micellar and Non- micellar Sodium Octanoate, 2593 Coupled 13C Longitudinal and Transverse Solubilities Kinetics of Reaction with Hydroxide Ions and Solubilities of Iron(n) Complex Cations in Aqueous Urea Solutions. Derivation of Transfer Chemical Potentials for Initial and Transition States, 559xxviii SUBJECT INDEX Solubilities (cont.) Pairwise Gibbs Function Cosphere-Cosphere Group Interaction Parameters for Alkylammonium Salts in Aqueous Solutions at 298 K; Solubilities of Hydrocarbons in Aqueous Salt Solutions, 3039 Benzonitrile derived from Solubility and Complexing Data, 1569 Single-ion Free Energies for Transfers to Solution Chemistry The Molar Volume of a Large Polymeric Cation Setschenow Coefficients for Caffeine, Theophylline ~A1,,O4,H,,l7+, 1725 and Theobromine in Aqueous Electrolyte Solutions, 1029 inducing Solid Particle Motion, Orientation and Related Effects in a Solute Concentration Gradient, 1269 Internal Pressures, Temperatures of Maximum Density and Related Properties of Water and Deuterium Oxide, 1783 Reactions of Alkylperoxyl Radicals in Solution. Part 1.-A Kinetic Study of Self-reactions of 2- Propylperoxyl Radicals between 135 and 300 K, 242 1 Solvation Origin of Idealized Static Thermodynamic Forces The Thermodynamics of Solvation of Ions.Part 2.-The Enthalpy of Hydration at 298.15 K, 339 Ionic Solvation in Water-Cosolvent Mixtures. Part 13.-Free Energies of Transfer of Single Ions from Water into Water-Tetrahydrofuran Mixtures, 439 Local Polarity of Solvent Mixtures in the Field of Electronically Excited Molecules and Exciplexes, 495 Cluster Size Distribution in a Monte Carlo Simulation of the Micellar Phase of an Amphiphile and Solvent Mixture, 2905 The Thermodynamics of Solvation of Ions. Part 4.-Application of the Tetraphenylarsonium Tetraphenylborate (TATB) Extrathermodynamic Assumption to the Hydration of Ions and to Properties of Hydrated Ions, 2985 Solvent-exchange Reactions of Metal Ions.Diagnosis of Mechanisms in Terms of the Bond Order of the Activated Complexes, 431 Dichlorobis( I ,2-diaminoethane)cobalt(111) Ion in Water and in Water-t-Butyl Alcohol Mixtures, I119 Effect of Solvent on the Reactions of Coordination Complexes. Part 1 .-Kinetics of Solvolysis of the cis- (Bromo)(benzimidazole)bis(ethylenediamine)cobalt( I in Methanol-Water Media, 2505 Kinetics of the Solvolysis of the cis- sorpdor, Smectite Molecular Sieves. Part 2.-Expanded Fluorhectorite Sorbents, 779 SoraJ..veh&y Measurements Volume and Compressibility Changes in Mixed- salt Solutions at 25 "C, 2467 --try Influence of Mixed Cerium(1v) Sulphate and Ferroin Catalysts on the Oscillatory Redox Reaction between Malonic Acid and Bromate, 267 Free Energies, Enthalpies and Entropies of the Monothiocyanate Complex Formation of Trivalent Metals in Dimethyl Sulphoxide Solutions, 1253 Ionic Solvation in Water-Cosolvent Mixtures. Part I4.-Free Energies of Transfer of Single Ions from Water into Water-Ethylene Carbonate and Water-Propylene Carbonate Mixtures, 128 I Cyclodextrins.A '@F Nuclear Magnetic Resonance and Spectrophotometric Study, 2697 The Inclusion of Tropaeolin O00 No. 2 by Permethylated P-Cyclodextrin. A Kinetic and Equilibrium Study, 275 I Cyclodextrin. A Kinetic and Equilibrium Study, 3237 The Inclusion of Diflunisal by a- and P- The Inclusion of Pyronine Y by P- and y- Spin Friction Coefficients Concentration Dependence of Spin Friction Coefficients in Suspensions of Parallel Cylinders and Spheres, 547 Spin Trapping 219 Spin-trapping Study of the Radiolysis of CCl,, High-performance Liquid Chromatography-Electron Spin Resonance Analysis of Sugars irradiated in the Solid and Liquid Phase, 225 Spin-Lattice Relaxation Crystals, 3709 Stability Constants N; and (CN); Spin-Lattice Relaxation in KCN Estimations of Stability Constants by Potentiometry of some Lanthanum and Erbium Dicarboxylates at Constant Ionic Strength, 425 Determination of Stability Constants from Linear- scan or Cyclic-voltammetric Data using a Non- linear Least-squares Method, 1719 Thiocyanate in N,N-Dimethylformamide, 226 1 Metal-ion Dibenzocryptates, 2663 Ionization Equilibria in Solutions of Cobalt(I1) Complexation and Transfer Free Energies of Statistical Mechanics Monolayer Adsorption of Non-spherical Molecules on Solid Surfaces. Part 1 .-Adsorption of Hard Dumb-bells on Flat Surfaces, 1405 Structural Defects Investigation of Internal Silanol Groups as Structural Defects in ZSM-5-type Zeolites, 3459 Sugars High-performance Liquid 11) Chromatography-Electron Spin Resonance Analysis of Sugars irradiated in the Solid and Liquid Phase, 225 Radiation Damage in a Phosphated Sugar.An Electron Spin Resonance Study of Phosphorus- centred Radicals Trapped in an X-Irradiated Single Crystal of a Phenoxyphosphoryi Xylofuranose Derivative, 401 Sulpbamic Acid Single-crystal Proton ENDOR of the SO; Centre in y-Irradiated Sulphamic Acid, 3717SUBJECT INDEX xxix Sulphur Radical Cations of Trialkylphosphine Oxides, Trialkylphosphates, Hexamethylphosphoramide, Dimethyl Sulphoxide and various Sulphones, Sulphites and Sulphates.An Electron Spin Resonance and Radiation Chemical Study, 383 Effects of the Oxidation State of Cerium on the Reactivity and Sulphur Resistance of Nio/ Zeolite, Nio/Silica and Nio/CeO, Catalysts in Butane Hydrogenolysis, 1 137 Sulphuric Acid Oxidation of 2,4-Dibromo-6-nitroaniline in Aqueous Sulphuric Acid Solutions on a Platinum Electrode, 2619 Superoxide Dismutase The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach, 3669 Supported Heteropoly Acids Electron Spin Resonance Studies of Free and Supported 12-Heteropoly Acids. Part 6.-The Investigation of Reduced H4(SiW,,04,) - x H,O and Ag,(SiW,,O,,)-x H,O and the Effects of Oxygen Adsorption, 3 1 15 Surface Chemistry A Fourier-transform Infrared and Catalytic Study of the Evolution of the Surface Acidity of Zirconium Phosphate following Heat Treatment, 853 Temperatures in Ceramic Electrolyte Cells, 289 Reactions for Propylene and Methane over a-Bi,O,, 463 Surface Chemistry revealed by Electrical Conductance Variations, 1323 Temperature-programmed Desorption Study of the Interactions of H,, CO and CO, with LaMnO,, 3149 Pentanol -Sodium Dodecyl Sulphate Micelles, 59 1 Local Structure of Nickel Oxide grown at High CH Bond Activation and Radical-Surface Tin Dioxide Gas Sensors.Part 1.-Aspects of the Surface Potential Measurements in Surfactan t Acrylonitrile Polymerization from Aqueous Solution. The Role of Surfactants, 645 Hemimicelle Formation of Cationic Surfactants at Silica Gel-Water Interface, 267 1 Kinetic and Equilibrium Studies associated with the Aggregation of Non-ionic Surfactants in Non-polar Solvents, 2735 A 'H and 13C Nuclear Magnetic Resonance Study of the Conformation of Aerosol OT in Water and Hydrocarbon Solutions, 5 17 Characterisation of Aerosol OT-stabilised Oil-in- water Microemulsions using a Time-resolved Fluorescence Method, 1493 'H and 13C Nuclear Magnetic Relaxation Studies of the Cubic Liquid-crystalline Phase I, in the Sodium Octanoate-Octane-Water System, 15 15 Oil-Water-Surfactant Systems.Effects of Cosurfactant in Systems containing Sodium Dodecyl Sulphate, 2347 Infrared Study of the Adsorption of Non-ionic Surfactants on Silica, 3283 Interfacial Tension Minima in Infrared Study of the Desorption of Polycondensed Aromatic Compounds by Non- ionic Surfactants at the Silica-Carbon Tetrachloride Interface, 3295 Syngas Promotion of Platinum-based Catalysts for Methanol Synthesis from Syngas, 2 1 13 TCNQ Electron Nuclear Double Resonance of S = 1/2 Defects in a Single Crystal of the Morpholinium-TCNQ 1 : 1 Complex, 57 Temperature-programmed Desorption Aspects of Temperature-programmed Analysis of some Gas-Solid Reactions.Part 2.-Hydrogen Temperature-programmed Desorption from Silica-supported Platinum, 1369 Y Zeolite by Temperature-programmed Desorption and Infrared Techniques, 2605 Study of the Support Evolution through the Characterization of C@Rh species formed on Rh- Temperature-programmed Reduction Process of Preparation of Rhodium/Lanthana Catalysts, 2279 Reducibilities of Nickel and Cobalt Faujasites, 3015 Non-isothermal Reduction Kinetics and Ternary Systems Calorimetric Investigations of Association in Ternary Systems.Part 4.-The Influence of Solvation on Enthalpy of Complex Formation in Phenol-Tetrahydrofuran and 2,6- Dimethylphenol-Tetrahydrofuran Systems, 3083 Tetra-akylammonium Salts Volume and Compressibility Changes in Mixed- salt Solutions at 25 "C, 2467 Enthalpies of Transfer of Tetra-alkylammonium Halides from Water to Water-Propan- 1-01 Mixtures at 25 "C, 2585 Ion-pair Formation by Tetra-alkylammonium Ions in Methanol. A Nuclear Magnetic Resonance Study, 3419 Tetrahydro fur an The Study of Aluminium Deposition from Tetrahydrofuran Solutions of AlCl,-LiAlH, using Microelectrodes.Part 1.-1: I AICI, -LiAIH,, 2787 Tetrahydrofuran Solutions of AlCl,-LiAlH, using Microelectrodes. Part 2.-The Influence of Solution Composition, 2795 Ternary Systems. Part 4.-The Influence of Solvation on Enthalpy of Complex Formation in Phenol-Tetrahydrofuran and 2,6- Dimethylphenol-Tetrahydrofuran Systems, 3083 Tetraphenylarsonium Tetrapbenylborate Assumption The Thermodynamics of Solvation of Ions. Part 4.-Application of the Tetraphenylarsonium Tetraphenylborate (TATB) Extrathermodynamic Assumption to the Hydration of Ions and to Properties of Hydrated Ions, 2985 The Study of Aluminium Deposition from Calorimetric Investigations of Association in Thermal Analysis Catalytic Properties of Synthetic Faujasites Modified with Fluoride Anions, 535xxx SUBJECT INDEX Thermal Desorption The Effect of Hydrogen Sulphide on the Adsorption and Thermal Desorption of Carbon Monoxide over Rhodium Catalysts, 1835 Thermodynamics The Thermodynamics of Solvation of Ions.Part 2.-The Enthalpy of Hydration at 298.15 K, 339 Ionic Solvation in Water-Cosolvent Mixtures. Part 13.-Free Energies of Transfer of Single Ions from Water into Water-Tetrahydrofuran Mixtures, 439 Thermodynamics of Mixtures with a Hexane Isomer. Excess Volumes of 1 -Chlorohexane with a Hexane Isomer at 298.15 K, 819 A Phenomenological Approach to Micellisation Kinetics, 967 Theoretical Analysis of Activation Parameters in Mixed Solvents Involving Various Chemical Equilibria. Reaction of Ethyl Iodide with Bromide Ion in N-Methylacetamide-Acetonitrile and N-Methylacetamide-N,N,- Dimethylacetamide Mixtures, 1089 inducing Solid Particle Motion, Orientation and Related Effects in a Solute Concentration Gradient, 1269 Compounds, 1553 Benzonitrile derived from Solubility and Complexing Data, 1569 Internal Pressures, Temperatures of Maximum Density and Related Properties of Water and Deuterium Oxide, 1783 Constants and Enthalpies of Complexation for 72 Monomeric Hydrogen-bond Acids with N- Methylpyrrolidinone in l,l, 1-Trichloroethane, 2867 Chemical Equilibria and Kinetics at Constant Pressure and at Constant Volume, 2901 Effusion Mass Spectrometric Determination of Thermodynamic Properties of the Gaseous Mono- and Di-hydroxides of Calcium and KCaO(g), 3229 Origin of Idealized Static Thermodynamic Forces Thermodynamic Stability of Solid Intermolecular Single-ion Free Energies for Transfers to Hydrogen Bonding.Part 2.-Equilibrium Tbermogr avimetry Tin Oxide Surfaces. Part 17.-An Infrared and Thermogravimetric Analysis of the Thermal Dehydration of Tin(1v) Oxide Gel, 3383 Thin Films Adsorptive Properties of Semiconducting Thin NiO and TiO, Films combined with an Oppositely Polarized Ferroelectric Support, 306 1 Thiopheoe Adsorption of Thiophene and Model Hydrocarbons on Mo03/y-Al,03 Catalysts studied by Gas-Solid Chromatography, 1 179 Thiyl Radicals Direct Observation of a 1,4-Hydrogen Shift in Vinyl Radicals derived from the Reaction of Alkynes with Thiyl Radicals, 77 Thorium A Study of the Adsorption Sites on Thoria by Scanning Transmission Electron Microscopyand Adsorption and Desorption of Water and Methanol, 1417 Thymidine Selective 'H-13C and 'H-'H Nuclear Overhauser Enhancement Studies of Adenosine-Thymidine Interaction in Solution, 1731 Time-resolved Reflection Spectroscopy Time-resolved Reflection Spectrum of Ordered Structure of Monodispersed Polystyrene Spheres in an Electric Field, 2487 Effect of Neutral Polymers on the Ordering of Monodispersed Polystyrene Spheres, 2497 Tin Dioxide Gas Sensors. Part 1.-Aspects of the Tin Surface Chemistry revealed by Electrical Conductance Variations, 1323 Tin Oxide Surfaces.Part 17.-An Infrared and Thermogravimetric Analysis of the Thermal Dehydration of Tin(Iv) Oxide Gel, 3383 Titanium The Effects of Titania and Alumina Overlayers on the Hydrogenation of CO over Rhodium, 2061 An In Situ Mossbauer Spectroscopic Investigation of Titania-supported Iron-Ruthenium Catalysts, 2573 The Identification and Characterisation of Mixed Oxidation States at Oxidised Titanium Surfaces by Analysis of X-Ray Photoelectron Spectra, 351 Phosphate Glasses containing Ruthenium and Titanium Ions, 705 Binding of Paramagnetic Ions in Ionomers.Cu2+ and Ti3+ in Nafion Membranes, 3575 Dielectric Behaviour of Adsorbed Water. Part 1 .-Measurement at Room Temperature on TiO,, 943 2.-Measurement at Low Temperatures on TiO,, 957 Structural Effects on the Adsorption of Alcohols on Titanium Dioxides, 1591 Adsorption of Organic Molecules on a Titanium Dioxide (Rutile) Surface, 1739 Infrared Studies on Dinitrogen and Dihydrogen adsorbed over TiO, at Low Temperatures, 2765 Adsorptive Properties of Semiconducting Thin NiO and TiO, Films combined with an Oppositely Polarized Ferroelectric Support, 306 1 An Electron Spin Resonance Study of Rutile and Anatase Titanium Dioxide Polycrystalline Powders treated with Transition-metal Ions, 3541 ReIV in TiO,, 3613 Optical and Spectromagnetical Properties of Dielectric Behaviour of Adsorbed Water.Part The Electron Spin Resonance Powder Spectrum of Toluene Activity and Selectivity in Toluene Oxidation on Well Characterized Vanadium Oxide Catalysts, 3303 Tracer Diffusion Coefficients Measurements of Tracer Diffusion Coefficients of Lithium Ions, Chloride Ions and Water in Fourier-transform Infrared Spectroscopy. Aqueous Lithium Chloride Solutions, 1779SUBJECT INDEX xxxi Transfer Energies Standard Gibbs Free Energies of Transfer of NaCl and KC1 from Water to Mixtures of the Four Isomers of Butyl Alcohol with Water.The Use of Ion-selective Electrodes to Study the Thermodynamics of Solutions, 635 Complexation and Transfer Free Energies of Metal-ion Dibenzocryptates, 2663 Transfer Enthalpies Microcalorimetric Measurement of the Enthalpies of Transfer of a Series of ortho- and para- Alkoxyphenols from Water to Octan-1-01 and from Isotonic Solution to Escherichia coli Cells, 2705 Transition Metals Coordination of Carbon Monoxide to Transition- metal Surfaces, 19 1 5 Electron Spin Resonance Studies of HPt(CN)2,- and Pt(CN):- formed by Irradiation of K, Pt(CN), in Solvents, 2803 Transmission Electron Microscopy Thermally Activated Ruthenium Dioxide Hydrate. A Reproducible, Stable Oxygen Catalyst, 233 1 Transport Phenomena in Concentrated Aqueous Solutions of Sodium-Caesium Polystyrene Sulphonates, 3259 Transport Phenomena Trichloroacetic Acid 35Cl Nuclear Quadrupole Resonance and Infrared Spectroscopic Studies of Hydrogen Bonding in Complexes of Trichloroacetic Acid with Various Nitrogen and Oxygen Bases, 2541 Trichlorofluoromethane Heterogeneous Decomposition of Trichlorofluorornethane on Carbonaceous Surfaces, 3055 Triethylammonium Salts Infrared Spectroscopic Studies of Hydrogen Bonding in Triethylammonium Salts.Part 4.-Rearrangement of Hydrogen-bonded Ion Pairs of Triethylammonium Salts caused by Interaction with Tetrabutylammonium Salts in Solution, 1879 Trinitrotoluene Electron-donor-Electron-acceptor Association Constants of Pyrene with 2,4,6-Trinitrotoluene in Solution determined by 'H-Nuclear Magnetic Resonance from Non-linear Scatchard Plots, 2641 Tri-n-octylammonium Bromide Non-ideal Behaviour of Benzene Solutions of Tri- n-octylammonium Bromide and Cyclohexanol, 231 1 TRIPLE The Use of Electron Spin Resonance and ENDOR and TRIPLE Resonance Methods for Structural Elucidation.Isomeric 10,lO- Diphenylphenanthren-9( IOH)-ones, 43 Electron Spin Resonance, ENDOR and TRIPLE Resonance of some 9,lO-Anthraquinone and 9,10-Anthraquinol Radicals in Solution, 5 1 Multiple Resonances involving Electron Spin Resonance, Nuclear Magnetic Resonance and Optical Transitions: More than Just a Game?, 3469 Tropaeolin The Inclusion of Tropaeolin 000 No.2 by Permethylated P-Cyclodextrin. A Kinetic and Equilibrium Study, 275 1 Tungsten Promotion of Nitrogen and Hydrogen Chemisorption and Ammonia Synthesis on Alumina-supported Hexagonal Tungsten Bronze, K, WO,, 2175 Ultrasonic Relaxation Ultrasonic Relaxation Studies associated with the Interactions of Acetic Acid with Some Polyvinylpyridines in Aqueous Solution, 2525 Rotational Isomers using Ultrasonic Spectroscopy. Part 1 .-1 -Chloro-2- met h y lpro pane and 1 - B romo- 2- met h y lpr o pane, 527 Study of the Conformational Equilibria between Ultraviolet-Visible Spectroscopy Ultraviolet-Visible Reflectance Studies of Hydrogen Adsorption and CO-H, Interaction at MgO and CaO Surfaces, 1237 Phosphate Glasses containing Ruthenium and Titanium Ions, 705 1469 Uranium Optical and Spectromagnetical Properties of Adsorption of Benzene on Acidified Alumina, Study of the Electronic Structure of UBr, using X- Oxidation of Crystalline UO, studied using X-Ray Ray Photoelectron Spectroscopy, 1355 Photoelectron Spectroscopy and X-Ray Diffraction, 925 Vanadium Comparison of Hydrogenation and H ydrogenolysis on Unsupported and Silica- supported Rh-V,O, and Pt-V,O,, 209 1 Electron Spin Kesonance Studies of Free and Supported 12-Heteropoly Acids.Part 5.- Elucidation of Structures of Hydrated and of Dehydrated Heteropoly Acids by Quantum Chemical Calculations of Electron Spin Resonance Parameters, 104 1 An Electron Spin Resonance Study of Complexes of Oxovanadium(1v) with Simple Dicarboxylic Acids, 3513 Structures of Vanadium Oxide on Various Supports, 675 Activity and Selectivity in Toluene Oxidation on Well Characterized Vanadium Oxide Catalysts, 3303 Fourier-transform Infrared Investigation of Vapour Pressure The Vapour Pressure of Benzene.Part 1.-An Assessment of Some Vapour-pressure Equations, 2709 2.-Saturated Vapour Pressures from 279 to 300 K, 2719 The Vapour Pressure of Benzene. Part Vinyl Radicals Direct Observation of a IP-Hydrogen Shift in Vinyl Radicals derived from the Reaction of Alkynes with Thiyl Radicals, 77xxxii SUBJECT INDEX Viologen Synthesis of Montmorillonite-Viologen Intercalation Compounds and their Photochromic Behaviour, 185 1 Radical Spectra and Product Distribution following Electrophilic Attack by the OH’ Radical on 4-Hydroxybenzoic Acid and Subsequent Oxidation, 3 177 Virial Coefficient One-dimensional Rare Gases in the Pores of Ferrierite and their Virial Coefficients, 33 17 Virus Electron Spin Resonance and Saturation Transfer Electron Spin Resonance of Virus and Membrane Systems, 203 Viscosity Thermodynamic Properties of the PMMA-Acetonitrile-l,4-Dioxane System, 2289 Dynamic Properties and Structure of Salt-free Polystyrene Sulphonate Solutions, 801 Self-consistency of the Percolation Model as applied to a Macrofluid-like Water-in-Oil Microemulsion, 162 1 The Mechanism of Conductivity of Liquid Polymer Electrolytes, 3345 Vitamin B12 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(I1) “,I-Macrocyclic Complexes. A Means of Breaking the Co-C Bond in B12 Co-enzyme, 3663 Volt ammetry Oxidation of 2,4-Dibromo-6-nitroaniline in Aqueous Sulphuric Acid Solutions on a Platinum Electrode, 2619 Water Dielectric Behaviour of Adsorbed Water.Part 2.-Measurement at Low Temperatures on TiO,, 957 Density and Related Properties of Water and Deuterium Oxide, 1783 Internal Pressures, Temperatures of Maximum Water Gas Promotion of Methanol Synthesis and the Water- gas Shift Reactions by Adsorbed Oxygen on Supported Copper Catalysts, 2 193 Water-Cosolvent Mixtures Ionic Solvation in Water-Cosolvent Mixtures. Part 13.-Free Energies of Transfer of Single Ions from Water into Water-Tetrahydrofuran Mixtures, 439 XANES Local Structure of Nickel Oxide grown at High Structure of the Catalytic Site on the Silica- Temperatures in Ceramic Electrolyte Cells, 289 supported Catalyst derived from Copper(ii) Acetate, 1227 Xanthiws Setschenow Coefficients for Caffeine, Theophylline and Theobromine in Aqueous Electrolyte Solutions, 1029 Xenon 12’Xe Nuclear Magnetic Resonance Study of Xenon adsorbed on Zeolite NaY exchanged with Alkali-metal and Alkaline-earth Cations, 45 1 X-Ray Absorption Fine Structure Extended X-Ray Absorption Fine Structure Study of the Reaction between Silica-supported Copper(i1) Oxide Catalysts and Acetic Acid.2635 X-Ray Diffraction The Crystal Structure of Sodium Diheptylsulphosuccinate Dihydrate and Comparison with Phospholipids, 3093 Photoelectron Spectroscopy and X-Ray Diffraction, 925 The Nature of Supported-molybdena Catalysts. Evidence from a Raman and X-Ray Diffraction Investigation of Pyridine Adsorption, 1601 Catalytic Activity and Structure of Mo Oxide Highly Dispersed on ZrO, for Oxidation Reactions, 176 1 Rb, 3447 Differential Thermal Analysis, X-Ray Powder Diffraction and Electrical Conductivity Studies on the Motion of Cations, including Self- diffusion in Crystals of Propylammonium Chloride and Bromide as well as their N- Deuterated Analogues, 3207 Oxidation of Crystalline UO, studied using X-Ray Structure of Second-stage Graphite-Rubidium, C,, Hydrogen- 1 Nuclear Magnetic Resonance, X-Ray Photoelectron Spectroscopy The Identification and Characterisation of Mixed Oxidation States at Oxidised Titanium Surfaces by Analysis of X-Ray Photoelectron Spectra, 351 Surface of Y Zeolites Dealuminated with SiCl, Vapour.Influence of Conditions of Dealumination, 5 1 I y-Al,O, doped with Sodium Ions, 627 Photoelectron Spectroscopy and X-Ray Diffraction, 925 Nature of Oxide-supported Copper(ii) Ions and Copper derived from Copper(ii) Chloride, 1347 Study of the Electronic Structure of UBr, using X- Ray Photoelectron Spectroscopy, 1355 An X-Ray Photoelectron Spectroscopy Study of the Influence of Hydrogen on the Oxygen-Silver Interaction, 3161 327 1 Aluminium Distribution in the Bulk and on the Kinetics of N,O Decomposition on the Surface of Oxidation of Crystalline UO, studied using X-Ray Hydrazine Reduction of Transition-metal Oxides, X-Rays An Electron Spin Resonance Study of Single Crystals of X-irradiated L-Ascorbic Acid at Room Temperature.Experimental Results and Semiempirical Calculations, 893 Zeolite Dealumination of Sodium Y Zeolite with Characterization of C S R h species formed on Rh- Hydrochloric Acid, 153 1 Y Zeolite by Temperature-programmed Desorption and Infrared Techniques, 2605 Determination of the Distribution of Aluminium in Zeolitic Frameworks, 268 1 Neutron Spectroscopic Study of Polycrystalline Benzene and of Benzene adsorbed in Na-Y Zeolite, 3199INDEX xxxiii "T 7- I,-_- 3ULSJCL 1 Zeolite (cont.) Investigation of Internal Silanol Groups as Structural Defects in ZSM-5-type Zeolites, 3459 Exchange of Oxygen Isotopes between Carbon Dioxide and Ion-exchanged Zeolites A, 41 1 lz9Xe Nuclear Magnetic Resonance Study of Xenon adsorbed on Zeolite NaY exchanged with Alkali-metal and Alkaline-earth Cations, 45 1 Incorporation and Stability of Iron in Molecular- sieve Structures.Ferrisilicate Analogues of Zeolite ZSM-5, 487 Aluminium Distribution in the Bulk and on the Surface of Y Zeolites Dealuminated with SiCl, Vapour.Influence of Conditions of Dealumination, 51 1 Catalytic Properties of Synthetic Faujasites Modified with Fluoride Anions, 535 Hydrocarbon Formation from Methylating Agents over the Zeolite Catalyst ZSM-5. Comments on the Mechanism of Carbonxarbon Bond and Methane Formation, 571 Formation of Carbocations from C, Compounds in Zeolites of Different Acidities, 1109 Fourier-transform Infrared Study of the Role of Zeolite Lewis Sites in Methanol Reactions over HZSM-5 Surfaces, 1149 Origin of Boron Mobility over Boron-impregnated ZSM-5. A Combined High-resolution-Solid- state llB Nuclear Magnetic Resonancejhfrared Spectral Investigation, 175 1 Comments on the Mechanism of MTG/HZSM-5 Conversion, 177 1 Nuclear Magnetic Resonance Self-diffusion Studies of Methanol-Water Mixtures in Pentad-type Zeolites, 1843 ZSM-5 containing Co-adsorbed Benzene, and the Location of the Benzene Molecules, 2301 Transformation of But- I-ene into Aromatic Hydrocarbons over ZSM-5 Zeolites, 2913 Molecular Mobility of Methane adsorbed on Zinc Physicochemical Characterization of ZnO/Al,O, and Zn0-MoO3/A1,O3 Catalysts, 665 Propan-2-01 Adsorption and Decomposition on Zinc Oxide promoted by Alkali Metal, 2227 Reactions of Alkenes and the Equilibration of Hydrogen and Deuterium on Zirconia, 3069 A Fourier-transform Infrared and Catalytic Study of the Evolution of the Surface Acidity of Zirconium Phosphate following Heat Treatment, 853 ZirconiumCumulative Author Index 1987 Abraham, M.H., 2867 Agnel, J-P. L., 225 Aika, K., 3139 Akalay, I., 1137 Akasheh, T., 2525, 3415 Akitt, J. W., 1725 Albano, K., 2113 Alberti, A., 91 Albery, W. J., 2407 Alexandrova, I., 2841 Ali, A.-K. M., 2391 Allen, G. C., 925, 1355 Alonso-Amigo, M. G., 3575 Amorebieta, V. T., 3055 Amorelli, A., 3541 Andersen, A., 2140 Anderson, A. B., 463 Anderson, J. B. F., 913 Anderson, M. W., 3505 Anderson, R. F., 3177 Angerand, F., 3355 Antholine, W. E., 151, 3675 Ardizzone, S., 1159 Arias, S., 2619 Arriaga, P., 2705 Atay, N. Z., 2407 Atherton, N. M., 37, 941, 3227, 3717 Au, C-T., 2047 Aun Tan, S . , 2035 Aveyard, R., 2347 Avnir, D., 1685 Axelsen, V., 107 Bacci, M., 3693 Bahneman, D. W., 2559 Baird, M. C., 3535 Baker, B.G., 2136 Baldini, G., 1609 Ball, R. C., 2515 Baion, M., 1029 Barford, W., 2515 Barqawi, K., 3415 Barratt, M. D., 135 Barrer, R. M., 779 Barthel, J., 3419 Bartok, M., 2359 Basosi, R., 151, 3675 Bastein, A. G. T. M., 2103, 2129 ’ Bastl, Z., 51 1 Bateman, J. B., 841 Battesti, C. M., 225 Baussart, H., 1711 Beaumont, P. C., 3415 Beck, W. F., 3635 Becker, K. A., 535 Bednarek, J., 3725, 3737 Beezer, A. E., 2705 Bell, A. T., 2061, 2086, 2087, Benfield, R. E., 3527 Bennett, J. E., 1805, 2421, 2433 Berclaz, T., 401 Berleur, F., 177 Bernal, S., 2279 Berroa de Ponce, H., 1569 Berry, F. J., 615, 2573 Bertagnolli, H., 687 Berthelot, J., 231 Beyer, H. K., 511 Bianchi, H., 3027 Bianconi, A., 289 Binks, B. P., 2347 Bird, R., 3069 Bjorklund, R. B., 1507 Blandamer, M.J., 559, 865, 1783, 3039 Blyth, G., 751 Boerio-Goates, J., 1553 Bogge, H., 2157 Bond, G. C., 1963, 2071, 2088, 2129, 2130, 2133, 2138, 2140 Borbely, G., 51 1 Botana, F. J., 2279 Boucher, E. A., 1269 Bowers, D. H., 3271 Brandreth, B. J., 1835 Brandt, B. A., 2857 Braquet, P., 177 Brazdil, J. F., 463 Breault, R., 2119 Brede, O., 2365 Brillas, E., 2619, 2813 Briscoe, B. J., 938 Bruce, J. M., 85 Brudvig, G. W., 3635 Brunton, G., 2421, 2433 Brustolon, M., 69 Brycki, B., 2541 Budil, D. E., 13 Bugyi, L., 2015 Biilow, M., 1843, 3459 Burch, R., 913, 2087, 2130, 2134, 2135, 2141, 2250 Burgess, J., 559, 865, 1783, 3039 Burggraaf, A. J., 1485 Burke, L. D., 299 Busca, G., 853, 1591, 2213 Buscall, R., 873 Butt, J. B., 2757 Cairns, J. A., 913 Calves, J-Y., 3283, 3295 Cameron, G.G., 3345 2088, 3149 Caneschi, A., 3603 Cannistraro, S., 3693 Care, C. M., 2905 Carley, A. F., 351 Caro, J., 1843, 2301, 3459 Carthy, G., 2585 Cassidy, J. F., 231 Cattania, M. G., 3619 Celalyan-Berthier, A., 401 Chadwick, D., 2227 Chalker, P. R., 351 Chandra, H., 759 Chengyu, W., 2573 Chieux, P., 687 Chin, E., 3429 Chinchen, G. C., 2193, 3399 Chittofrati, A., 1 159 Choudhery, R. A., 2407 Christensen, P. A., 3001 Christmann, K., 1975 Chu, G., 2533 Chudek, J. A., 2641 Clark, B., 865 Clausen, B. S., 2157 Clifford, A. A., 751 Coates, J. H., 2697, 2751, 3237 Colin, A. C., 819 Coller, B. A. W., 645, 657 Coluccia, S., 477 Colussi, A. J., 3055 Compostizo, A., 819 Compton, R. G., 1261 Conway, B. E., 1063 Cooley, N. A., 3535 Copperthwaite, R. G., 2963 Cordischi, D., 3613 Corti, H.R., 3027, 3249, 3259 Corvaja, C., 57 Costa, J. M., 2619 Cottrell, M. R., 3039 Couillard, C., 125 Courbon, H., 697 Craven, J. B., 779 Crossland, W. A., 37 Cullis, C. F., 3227 Cummins, P. G., 2773 Cunningham, J., 2973 Czarnetzki, L., 3015 D’Alba, F., 267 Daniels, J., 3663 Danil de Namor, A. F., 1569, Darvell, B. W., 2953 Dash, A. C., 1307, 2505 Dash, N., 2505 Daverio, D., 705 Chu, D-Y., 635 2663 xxxivAUTHOR INDEX xxxv Davies, M. J., 1347 Davoli, I., 289 Dawber, J. G., 771 Day, P., 3225 de Beer, V. H. J., 2145 De Doncker, J., 125 De Laet, M., 125 de Paula, J. C., 3635 De Ranter, C . J., 257 Declerck, P. J., 257 Dega-Szafran, Z . , 2541 DeGray, J. A., 3565 Delafosse, D., 1137 Delahanty, J. N., 135 Delobel, R., 1711 Despeyroux, B. M., 2081, 2139, 2171, 2243, 2255 Di Lorenzo, S ., 267 Diaz Peiia, M., 819 Dimitrijevid, N. M., 1193 Dimov, A. D., 2841 do Carmo, L. C. S., 3709 Dodd, N. J. F., 85 Doddridge, B. G., 2697 Domen, K., 2765 Dongbai, L., 2573 Drew, M. G. B., 3093 Du, J., 2671 Duarte, M. A., 2133 Duce, P. P., 2867 Ducret, F., 141 Dudikova, L., 511 Dumont, M. F., 3493 Dusaucy, A-C., 125 Dutkiewicz, E., 2847 Edwards, P. P., 3527 Egerton, T. A., 3541 Eicke, H.-F., 1621 Elbing, E., 645, 657 Elders, J. M., 1725 Empis, J. M. A., 43 Endoh, A., 411 Engberts, J. B. F. N., 865 Engelhardt, L. M., 3663 Evans, J. C., 43, 135, 3541 Fahim, R. B., 1601 Fan, G., 323 Farber, M., 3229 Fatome, M., 177 Feakins, D., 2585 Fejes, P., 1109 Fernandez-Prini, R., 3027 Fierro, J. L. G., 3149 Finn, P. L., 3429 Fischer, C-H., 2559 Fitch, A.N., 3199 Fletcher, P.D. I., 985, 1493 Flint, N. J., 167 Formaro, L., 1159 Formosinho, S. J., 431 Forrester, A. R., 211 Forste, C., 2301 Forster, H., 1109 Foster, R., 2641 Fouassier, J. P., 2935 Fox, G. G., 2705 Fraissard, J., 451 Franchini, G. C., 3129 Freude, D., 1843 Freund, E., 1417 Fricke, R., 1041, 3115 Fujii, K., 675 Fujitsu, H., 1427 Fukada, S., 3207 Funabiki, T., 2883, 2895 Galli, P., 853 Gampp, H., 1719 Gao, Y., 2671 Garbowski, E., 1469 Garcia, R., 2279 Garrido, J., 1081 Garrido, J. A., 2813 Garrone, E., 1237 Gatteschi, D., 3603 Geary, J. M., 3429 Gellings, P. J., 1485 Geoffroy, M., 401 Germanus, A., 2301 Gervasini, A., 705, 2271, 3619 Giddings, S., 2317, 2331 Gilbert, B. C., 77 Gilbert, R. G., 1449 Goates, J. R., 1553 Goates, S. R., 1553 Goffredi, M., 1437 Golding, P.D., 1203, 2709, 2719 Goodby, J. W., 3429 Goodman, B. A., 3513, 3627, Goodman, D. W., 1963, 1967, 3683 2071, 2072, 2073, 2075, 2082, 2086, 2251 Goralski, P., 3083 Gottschalk, F., 571 Gozzi, D., 289 Grampp, G., 161 Grant, R. B., 2035 Gratzel, M., 1101 Grauer, G. L., 1685 Grauer, Z., 1685 Gray, P., 751 Greci, L., 69 Green, M., 3663 Greenwood, P., 2663 Gribnau, M. C. M., 3493 Grieser, F., 591 Griffiths, J. F., 3226 Grigorian, K. R., 1189 Grimblot, J., 2170 Gross, R., 3549 Gross], L., 77 Groves, G. S., 11 19, 1281 Grzybkowski, W., 281, 1253, Gu, T., 2671 Guardado, P., 559 Guest, A., 3383 Guilleux, M.-F., 1137 Gunasekara, M. U., 2553 Hada, H., 1559 226 1 Hagele, G., 1055 Hakin, A. W., 559, 865, 1783, Halawani, K. H., 1281 Hall, D. G., 967 Hall, D.I., 2693 Hall, M. V. M., 571 Haller, G. L., 1965, 2072, 2080, 2089, 2091, 2129, 2131, 2132, 2133, 2135, 2136, 2137, 2138, 2243 3039 Halpern, A., 219 Hamada, K., 527 Hanke, V.-R., 2847 Harbach, C. A. J., 2035 Harendt, C., 1975 Harland, R. G., 1261 Harrer, W., 161 Harriman, A., 3001 Harris, R. K., 1055 Harrison, P. G., 3383 Hartland, G. V., 591 Hasegawa, A., 759, 2803 Hatayama, F., 675 Haul, R., 2083 Hayashi, K., 1795 Hayashi, O., 3061 Hayter, J. B., 2773 Healy, C. P., 2973 Heatley, F., 517, 2593 Hemminga, M. A,, 203 Henglein, A., 2559 Henriksson, U., 15 15 Hermann, R., 2365 Herold, B. J., 43 Hertz, H. G., 687 Hidalgo, J., 1029 Higgins, J. S., 939 Hikmat, N. A., 2391 Hilfiker, R., 1621 Hill, W., 2381 Hinderman, J. P., 21 19, 2142, Holden, J. G., 615 Holloway, S., 1935 Hongzhang, D., 2573 Hounslow, A.M., 2459, 2697 Howard, J. A., 3701 Howarth, J. N., 2787, 2795 Howe, A. M., 985, 1007 Howe, R. F., 813 Hudson, A., 91 Hunger, M., 1843, 3459 Hunter, R., 571 Hunter. W. H.. 2705 Hussein, F. H., 1631 Hutchings, G. J., 571. 2963 Ichikawa, K., 2925 Ikeda, R., 3207 Ikeyama, N., 1427 Imamura, H., 743 Imanaka, T., 665 Ingram, M. D.. 3345 Inoue, Y . , 3061 Ishikawa, T., 2605 2143XXXVl AUTHOR INDEX Ismail, H. M., 1601, 2835 Isobe, M., 3139 Isozumi,Y., , 2895 Ito, T., 451 Iwaki, T., 943, 957 Iwamoto, E., 1641 Jackson, S. D., 905, 1835 Jaenicke, W., 161, 2727 Janata, E., 2559 Janes, R., 383 JenE, F., 2857 Jerschkewitz, H-G., 31 15 Jobic, H., 3199 Johnson, I., 3331 Jones, P., 2735 Jonsson, B., 3331 Joyal, C. L. M., 2757 Joyner, R. W., 1945, 1965, 2074, 2085, 2138, 2249 Juszczyk, W., 1293 Kaim, W., 3549 Kakuta, N., 1227, 2635 Kaiinowski, H. J., 3709 Kameda, Y., 2925 Kaneko, M., 1539 Kanno, T., 721 Kapturkiewicz, A., 2727 Karger, J., 1843, 2301, 3459 Kariv-Miller, E., 1169 Karpinski, Z., 1293 Katime, I., 2289 Kato, C., 1851 Kawaguchi, T., 1579 Kazansky, V.B., 2381 Kazusaka, A., 1227, 2635 Keijzers, C. P., 3493, 3613 Kemball, C., 3069 Kerr, C W., 85 Kevan, L., 3505 Kido, K., 3139 Kiennemann, A., 21 19 King, D. A., 1966, 2001, 2079, Kinnaird, S., 3399 Kinoshita, N., 2765 Kira, A., 1539 Kiricsi, I., 1109 Kitagawa, H., 2913 Kitaguchi, K., 1395 Kiwi, J., 1101 Klein, J., 1703 Klinszporn, L., 226 1 Klofutar, C., 231 1 Knoche, W., 2847 Knozinger, H., 2088, 2171 Kobayashi, J., 1395 Kobayashi, M., 721 Koda, S., 527 Kondo, Y., 1089 Konishi, Y., 721 Koopmans, H.J. A., 1485 Kordulis, C . , 627 Korf, S. J., 1485 Korth, H-G., 95 Koutsoukos, P. G., 1477 2080, 2081 Kowalak, S., 535 Krell, M., 3419 Kristyan, S., 2825 Krusic, P. J., 3535 Kubelkova, L., 511 Kubokawa, Y., 675, 1761 Kumamaru, T., 1641 Kuroda, K., 1851 Kusabayashi, S., 1089 Kuzuya, M., 1579 La Ginestra, A., 853 Lackey, D., 2001 tajtar, L., 1405 Lambelet, P., 141 Lambert, R. M., 1963, 1964, 2035, 2082, 2083, 2084 Lamotte, J., 1417 Lang, N. D., 1935 Larher, Y., 3355 Laschi, F., 1731 Laurin, M., 2119 Lauter, H. J., 3199 Lavagnino, S., 477 Lavalley, J-C., 1417 Lawin, P. B., 1169 Lawrence, C., 2331 Lawrence, S., 1347 Le Bras, M., 1711 Leach, H. F., 3069 Leaist, D. G., 829 Lecomte, C., 177 Lee, E. F. T., 1531 Leeper, J.D., 3229 Lefferts, L., 3161 Lengeler, B., 2157 Lercher, J. A., 2080, 2255 Leroy, J-M., 1711 Letellier, P., 1725 Levin, M. E., 2061 Lijour, Y., 3283, 3295 Lima, M. C. P., 2705 Lin, C. P., 13 Lin, Y-J., 2091 Linares-Solano, A., 1081 Lincoln, S. F., 2459, 2697, 2751, Lindgren, M., 893, 1815 Lippens, B. C., 1485 Littrell, D. M., 3271 Liu, R-L., 635 Liu, T., 1063 Liu, Y., 2993 Liwu, L., 2573 Loliger, J., 141 Lorenzelli, V., 853, 1591 Loretto, M. H., 615 Lougnot, D. J., 2935 Lucassen, J., 3093 Luckham, P. F., 1703 Lund, A., 893, 1815, 1869 Luo, H., 2103 Lycourghiotis, A., 627, 1179 Lynch, J., 1417 Lyons, C. J., 645 Lyons, M. E. G., 299 3237 Machin, W. D., 1203, 2709, Maikowiak, M., 2541 MacLaren, J. M., 1945, 1965 Maestre, A., 1029 Maezawa, A., 665 Makela, R., 51 Malatesta, V., 3669 Manfredi, M., 1609 Maniero, A.L., 57, 69 Manzatti, W., 2213 Marchese, L., 477 Marcus, Y., 339, 2985 Mari, C. M., 705, 3587 Markarian, S. A., 1189 Martin Luengo, M. A., 1347, Martin-Martinez, J. M., 1081 Mashkovsky, A. A., 1879 Masiakowski, J. T., 893, 1869 Masliyah, J. H., 547 Matralis, H., 1179 Matsuda, T., 3107 Matsuura, H., 789 Maurice, Y., 3355 Maxwell, I. A., 1449 McAleer, J. F., 1323 McCarthy, S. J., 657 McDonald, J. A., 1007 McLain, S. J., 3535 McLauchlan, K. A., 29 McPhail, D. B., 3513, 3627, Mead, J., 2347 Mehandru, S. P., 463 Mehnert, R., 2365 Mehta, G., 2467 Meng, Q., 3565 Meriadeau, P., 2140 Meriaudeau, P., 21 13 Merwin, L. H., 1055 Micic, 0. I., 1127 Mijin, A., 2605 Mile, B., 3701 Miller, A-F., 3635 Mills, A., 2317, 2331, 2647 Mintchev, L., 2213 Miura, H., 3107 Miyahara, K., 1227 Miyamoto, A., 3303 Miyata, H., 675, 1761, 1851 Mobius, K., 3469 Mochida, I., 1427 Molina-Sabio, M., 1081 Monk, C.B., 425 Montagne, X., 1417 Morazzoni, F., 705, 2271, 3587, 3619, 3669 Mori, K., 3303 Morimoto, T., 943, 957 Moriyama, T., 3139 Morris, H., 3701 Morris, J. J., 2867 Morton, J. R., 3535 Moscinsky, L. C., 3675 2719 1651 3683AUTHOR INDEX xxxvii Moseley, P. T., 1323 Mosseri, S., 3001 Mostowicz, R., 3459 Moyer, J. W., 3229 Moyes, R. B., 905 Mozzanega, M-N., 697 Muller, A., 2157 Muiioz, M. A., 1029 Murakami, Y., 3303 Nabiullin, A. A.. 1879 Naccache, C., 21 13 Nagao, M., 1739 Nagaoka, T., 1823 Nair, V., 487 Naito, S., 2475 Nakai, S., 1579 Nakajima. T., 1315 Nakamura, D., 3207 Nakata, M., 2449 Napper, D.H., 1449 Narayanan, S., 733 Narducci, D., 705, 3587 Nath, J., 3167 Nayak, R. C., 1307 Naylor, G. R. S., 3447 Nazer, A. F. M., 11 19 Nebuka, K., 2605 Nedeljkovic, J. M., 1127 Nenadovic, M. T., I127 Neta, P., 3001 Niccolai, N., 1731 Niemann, W., 21 57 Nishida, S., 1795 Nogaj, B., 2541 Nomura, H., 527 Nomura, M., 1227, 1779, Nonaka, K., 3317 Norris, J. 0. W., 1323 Norris, J . R., 13 Nrarskov, J. K., 1935 Notheisz, F., 2359 Nukui, K., 743 Nuttall, S., 559 O’Brien, A. B., 371 Ochoa, J. R., 2289 Odinokov, S. E., 1879 Ogura, K., 1823 Ohlmann, G., 31 15 Ohno, M., 1559 Ohno, T., 675 Ohshima, K., 789 Okabayashi, H., 789 Okada, T., 3317 Okamoto, Y., 665 Okubo, T., 2487, 2497 Okuda, T., 1579 Okuhara, T., 1213 Oliva, C., 3717 Oliver, E. J., 3717 Olofsson, G., 3331 O’Malley, P.J. R., 2227 Onishi, T., 2765, 3139 Ono, T., 675, 1761 Ono, Y., 2913 Otsuka, K., 1315 Ott, J. B., 1553 Oyama, K., 3189 Page, F., 2641 Paljk, S., 231 1 Pallas, N. R., 585 Parry, D. J., 77 Parsons, B. J., 3415 Patel, I., 2317, 2331 Patel, J. S., 3429 Patel, K. B., 3177 Patil, K., 2467 Patrono, P., 853 Peden, C. H. F., 1967 Pedersen, E., 2157 Pedersen, J. A., 107 Pedulli, G. F., 91 Pellicciari-Bollini, L., 3669 Penar, J., 1405 Pendry, J. B., 1945 Penfold, J., 2773 Perez-Tejeda, P., 1029 Pethica, B. A., 585 Pethrick, R. A., 938 Pfeifer, H., 2301, 3459 Pichat, P., 697 Pielaszek, J., 1293 Pilarczyk, M., 281, 2261 Pilz, W., 2301 Pizzini, S., 705, 3587 Pletcher. D., 2787, 2795 Plonka, A,, 3725, 3737 Poels, E. K., 2140 Pogni, R., 151, 3675 Pomonis, P., 627 Pomonis, P.J., 1363 Ponec, V., 1964, 1965, 2071, 2072, 2074, 2083, 2103, 2136, 2138, 2139, 2244, 2251 2635 Preston, K. F., 3535 Price, C., 3224 Primet, M., 1469 Prins, R., 2087, 2136, 2137, 2145, 2169, 2170, 2172 Priolisi O., , 57 Pritchard, J., 1963, 2085, 2249 Prugnola, A., 173 1 Puchalska, D., 1253 Purushotham, V., 21 1 Radulovic, S., 559 Raffi, J. J., 225 Rajaram, R. R., 2130 Ramaraj, R., 1539 Ramirez, F., 2279 Ramis, G., 1591 Rees, L. V. C., 1531, 1843 Reijerse, E. J., 3493, 3613 Renouprez, A., 3199 Renyuan, T., 2573 Resasco, D. E., 2091 Rey, P., 3603 Reyes, P. N., 1347 Richards, D. G., 2138 Richoux, M-C., 3001 Richter-Mendau, J., 1843 Rieger, P. H., 3565 Riley, B. W., 2140, 2253 Ritschl, F., 1041 Riva, A., 2213 Riviere, J. C., 351 Roberts, M. W., 351, 2047, Robinson, B.H., 985, 1007, Rodriguez, R. M., 2813 Rodriguez-Izquierdo, J. M., Rodriguez-Reinoso, F., 1081 Rollins, K., 1347 Roman, V., 177 Romiio, M. J., 43 Rooney, J. J., 2077, 2080, 2086, 2089 d Ross, J. R. H., 3161 Rosseinsky, D. R., 231, 245 Rossi, C., 1731 Rowlands, C. C., 43, 135, 3541 Rubio, R. G., 819 Rudham, R., 1631, 3223 Sabbadini, M. G. C., 2271 Sakai, K., 2895 Sakai, T., 743, 1823 Sakakini, B., 1975 Sakata, Y., 2765 Sakurai, M., 2449 Salazar, F. F., 2663 Saleh, J. M., 2391 Salmeron, M., 2061 Salmon, T. M. F., 2421, 2433 Shnchez, M., 1029 Sanfilippo, D., 2213 Sangster, D. F., 657 Saraby-Reintjes, A., 271 Sato, K., 3061 Sato, T., 1559 Saucy, F., 141 Saumagne, P., 3283, 3295 Savoy, M-C., 141 Sayed, M. B., 1149, 1751, 1771 Schiller, R. L., 3237 Schlick. S., 3575 Scholten, J. J.F., 1966, 2073, Schuller, B., 2103 Schulz-Ekloff, G., 3015 Scotti, R., 3619, 3669 Seebode, J., 1109 Segal, M. G., 371 Segre, U., 69 Self, V. A., 2693 Sendoda, Y., 2913 Sermon, P. A., 1347, 1369, 1651, 1667, 2175, 2243, 2256, 2693 Seyedmonir, S.. 813 Shelimov, B. N., 2381 Sheppard, N., 1966, 2075 Shibata, Y., 3107 Sidahmed, I. M., 439 Simonian, L. K., 1189 Singh, G., 3167 Smith, B. V., 2705 2084, 2085, 2086, 2248, 3225 2407 2279 2246, 2255, 2257xxxviii AUTHOR INDEX Smith, D. H., 1381 Smith, G. V., 2359 Smith, J. R. L., 2421, 2433 Soderman, O., 1515 Sokolowski, S., 1405 Solymosi, F., 2015, 2074, 2078, 2081, 2082, 2086, 2137, 2142, 2247 Somorjai, G. A., 2061 Sorrie, G. A., 3345 Spencer, M. S., 2193, 2245, Srivastava, R. D., 3229 Stacy, A. M., 3527 Stam, P., 3493, 3613 Staples, E., 2773 Steenken, S., 113 Stevens, D.G., 29 Stevenson, S., 2175 Stone, F. S., 1237, 2080, 2084, Stratford, M. R. L., 3177 Strumolo, D., 2271, 3619 Stuckey, M., 2525 Su, Z., 2573 Suda, Y., 1739 Suematsu, H., 2605 Sugahara, Y., 1851 Sugiyama, K., 3107 Suppan, P., 495 Sustmann, R., 95 Suzuki, T., I213 Svetlitid, V., 1169 Swartz, H. M., 191 Swift, A. J., 1975 Symons, M. C. R., 1, 383, 759, Szafran, M., 2541 Szostak, R., 487 Tabner, B. J., 167 Taga, K., 789 Taiwo, F. A., 3653 Takahashi, N., 2605 Takaishi, T., 411, 2681, 3317 Tamagawa, H., 3189 Tan, W. K., 645 Tanaka, H., 1395, 3189 Tanaka, K., 1213, 1779, 1859 Tanaka, K-i., 1859 Tanimoto, M., 2475 Tannakone, K., 2553 Tascon, J. M. D., 3149 Tassi, L., 3129 Tatarchuk, B. J., 3271 Taylor, P.J., 2867 Tejuca, L. G., 3149 2246, 2247, 2248, 2249, 2250 2254 2803, 3419, 3653 Tempere, J.-F., 1137 Tempest, P. A., 925 Theocharis, C. R., 1601, 2835 Thiery, C. L., 225 Thomas, T. L., 487 Thomson, S. J., 1893, 1964, 1965, 2083 Thurai, M., 841 Tiddy, G. J. T., 2735 Tiezzi, E., 3675 Tilquin, B., 125 Timmons, R. B., 2825 Tkaczyk, M., 3083 Tomellini, M., 289 Tonge, J. S., 231, 245 Toprakcioglu, C., 1703 Topsere, H., 2157, 2169, 2171 Topsere, N-Y., 2157 Torregrosa, R., 1081 Tosi, G., 3129 Toyoshima, I., 1213 Trabalzini, L., 151 Trifiro, F., 2213, 2246, 2251, Tse, J. S., 3701 Tsuchiya, S., 743 Tsuiki, H., 1395, 3189 Tsukamoto, K., 789 Turner, J. C. R., 937 Tyler, J. W., 925, 1355 Ueno, A., 1395, 3189 Ukisu, Y., 1227, 2635 Uma, K., 733 Unwin, P. R., 1261 Vaccari, A., 2213 Vachon, A., 177 Valigi, M., 3613 van de Ven, T.G. M., 547 van den Boogert, J., 2103 van der Lee, G., 2103 van der Riet, M., 2963 van Ommen, J. G., 3161 van Santen, R. A., 1915, 1963, Varani, G., 1609 Vattis, D., 1179 Vickerman, J. C., 1975, 2075 Villani, R. P., 2751 Vincent, P. B., 225 Vink, H., 801, 941 Vissers, J. P. R., 2145 Vong, M. S. W., 1369, 1667 Vordonis, L., 627 Vuolle, M., 51 Vvedensky, D. D., 1945 Waddicor, J. I., 751 2254 1964, 2077, 2140, 2250 Waddington, D. J., 2421, 2433 Waghorne, W. E., 2585 Waller, A. M., 1261 Wang, E., 2993 Wang, Z-C., 3367 Waters, D. N., 1601 Waugh, K. C., 2193, 3223 Webb, G., 3399 Wells, C. F., 439, 939, 11 19, Wells, P. B., 905 Whalley, E., 2901 Whan, D. A., 2193 White, A., 2459 White, J. W., 3447 White, L. R., 591, 873 Whyman, R., 905 Wickramanayake, S., 2553 Williams, D.E., 1323 Williams, G., 2647 Williams, J. O., 323 Williams, R. J. P., 1885 Williams, W. J., 371 Wilson, H. R., 1885 Wilson, I. R., 645, 657 Wilson, R. B., 3635 Winstanley, D., 1835 Wojcik, D., 1253 Wurie, A. T., 1651 Wyatt, J. L., 2803 Wylie, D. M., 3717 Wyn-Jones, E., 2525, 2735 Xyla, A. G., 1477 Yamada, K., 743, 3107 Yamaguchi, T., 3189 Yamamoto, H., 3207 Yamamoto, Y., 1641, 1795 Yamasaki, S., 1641 Yamashita, H., 2883, 2895 Yanagihara, Y., 1579 Yanai, Y., 1641 Yangbo, F., 2533 Yariv, S., 1685 Yonezawa, Y., 1559 Yoshida, S., 2883, 2895 Yoshikawa, M., 2883 Yoshino, T., 1823 Yun, D. L., 2251 Zaki, M. I., 1601, 2835 Zanchini, C., 3603 Zhang, Q., 635 Zibrowius, B., 3459 Zikanova, A., 2301 Zsigmond, A.G., 2359 Zukal, A., 3015 1281JOURNAL OF THE CHEMICAL SOCIETY Faraday Transactions 11, Issue1 2,1987 Molecular and Chemical Physics For the benefit of readers of Faraday Transactions I, the contents list of Faraday Transactions 11, Issue 12, is reproduced below. 2 183 Dielectric Absorption of Various Symmetrically Substituted Compounds of the Type [CH,(CH,),],X in a Polystyrene Matrix M. S. Ahmed and S. Walker 2 19 1 Photoredox and Electrochemical Reactions of Water-soluble Gold Porphyrins T. Shimidzu, H. Segawa, T. Iyoda and K. Honda 220 1 Absorption Spectra of Molecules adsorbed on Light-scattering Media. Part 2.-Interpretation of Diffuse Relectance Data R. Grade, U. Kaden and D. Fassler An SCF-MX-Xa Study of the Bonding and Nuclear Quadrupole Coupling in 1 : l Complexes of Amines with Diatomic Halogens and Interhalogens G.Bowmaker and P. D. W. Boyd 2225 Large-amplitude Vibrations and Microwave Band Spectra. Part 1 .-Adamantan- 1-01 G. Corbelli, A. Degli Esposti, L. Favero, D. G. Lister and R. Cervellati 2235 Large-amplitude Vibrations and Microwave Band Spectra, Part 2.-Adamantamine G. Corbelli, A. Degli Esposti, L. Favero, D. G. Lister and R. Cervellati Are the Reactions Li+Na, and Na+K, Direct or Indirect? A Dynamics Study of Semiempirical Valence-bond Potential-energy Surfaces V. M. F. Morais and A. J. C. Varandas 2261 Zero-field Pulsed Response and Dipolar Couplings in Systems of Spin I = 1 Nuclei J. C. Pratt and A. Watton 2271 Ion Diffusion near Charged Surfaces. Exact Analytic Solutions D. Y. C. Chan 2287 An Ab Initio Molecular-orbital Study of the Structure and Spectroscopic Properties of Ch,AlH G.E. Quelch and I. H. Hillier 2295 Photophysical Properties of Ru-Cyano-poly(pyridine) Complexes. Acidity and Temperature Tuning of Luminescence Properties A. Juris, F. Barigelletti, V. Balzani, P. Belser and A. von Zelewsky 2307 A Chemical Interpretation of Vibrationally Induced Barriers to Hindered Internal Rotation T. A. Claxton and A. M. Graham 23 19 Kinetic Study of the Reactions of Ground-state Silicon Atoms, Si(3 with Buta- 1,3-diene and But-2-yne 2325 Measurement of Absolute Rate Data for the Reaction of Atomic Potassium, K(4,S1,,), with CF,Cl, CF,Cl,, CFCl,, CF,Br and SF, as a Function of Temperature by Time-resolved Atomic Resonance Absorption Spectroscopy at 1 = 404 nm [K(5,PJ) +- K(42S1,2)] 2211 2247 S.C. Basu and D. Husain D. Husain and Y. H. Lee xxxix2339 Corrigendum to Exchange Interaction in Linear Trimeric Copper (11) Complexes with Ferromagnetic and Antiferromagnetic Ground States S. Gehring, H. Astheimer and W. Haase The following papers were accepted for publication in Furaday Transactions Z during September 1987. 6/1989 Mixtures of Benzene and Chloroform near a Silica Gel with Grafted Poly(Ethy1ene Oxide) Chains H. Ben Quada, H. Hornrnel and A. P. Legrand 6/2 109 Cooperative Effects in Heterogeneous Catalysis. Part 2.-Analysis and Modelling of the Temperature Dependence of the Oscillating Catalytic CO Oxidation of Palladium Crystals supported by an Amorphous A1,0, Carrier P. J. Plath, K. Moller and N. I.Jaeger 7/328 Mechanistic Aspects of Oxidative Coupling of Methane over LaAlO, T. Tagawa and H. Imai 7/438 Interactions between Metal Cations and the Ionophore Lasalocid. Part 1 .-Complexing of Alkaline-earth Cations by Lasalocid, Bromolasalocid and Salicyclic Acid in Methanol J. Juillard, C. Tissier and G. Jeminet 7/652 Interactions between Metal Cations and the Ionophore Lasalocid. Part 2.-Gibbs Functions, Enthalpies and Entropies for Complexation of Alkali- metal Cations by Lasalocid and Bromolasalocid Hydrocarbon Formation form Methanol using WO,/Al,O, and H-ZSM-5 Catalysts. A Comparative Study of the Reaction Mechanisms R. Hunger, L. Jansen Van Rensberg and G. J. Hutching 7/761 Ionic Exchange between Aluminium Pectinates and Ca, MnI', CU" and FerI1 Ions in Aqueous Solution 7/768 Studies on the Reactivity of OH Radicals in Non-aqueous Solvents using Laser Flash Photolysis 7/852 An Electrostatic Approach to the Structure of Hydrated Lanthanoid Ions : [M(OH,)J3+ versus [M(OH,)J3+ 7/865 Characterization of N-Exchanged Montmorillonites by X-Ray Photoelectron Spectroscopy M. Stocker, K-J.Jens, T. Riis and J. K. Grepstad 7/909 Inhibition of the Thin-film Oxidation of n-Dodecane by Diphenylamine A. D. Ekechukwu and R. F. Simmons 7/910 Chiral Sulphur-containing Molecules in LB Films C. Georges, T. J. Lewis, J. P. Llewellyn, S. Salvagno, D. M. Taylor, C. J. M. Stirling and V. Vogel 7/919 Stochastic Interpretation of Lag Times for the Onset of Template Amplification in RNA Replication 7/930 Ionic Solvation in Water-Cosolvent Mixtures.Part 15.-Free Energies of Transfer of Single Ions from Water Into Water-Dimethylformamide Mixtures Coordination States of Divalent Transition Metal Perchlorates in HMPA Solutions Y. Pointud and J. Juillard 7/023 R. A. Jorge and A. P. Chagas T. Vidoczy, A. N. Blinov, G. Irinyi and D. Gal K. Miyakawa, Y. Kaizu and H. Kobayashi A. Fernandez I. M. Sidahmed and C. F. Wells W. Grzybkowski, M. Pilarczyk and L. K. Linszporn 7/962 xl7/965 7/994 7/ 1089 7/ 1 107 7/ 1 109 7/1110 7/114? 7/1168 7/1172 7/ 1208 7/1211 7/1212 7/ 1227 7/1261 7/ I398 Interactions between Metal Cations and the Ionophore Lasalocid. Part 3.-Mn2+, Fe2+, Co2+, Ni2+ and Zn2+ in Methanol P. Laubry, C. Tissier, G. Mousset and J. Juillard Calorimetric Study on the State of C,-C, Alcohols sorbed on Silicalite H.Tharnm Activity Measurements and Spectroscopic Studies of the Catalytic Oxidation of Toluene over Silica-supported Vanadium Oxides B. Jonson, B. Rebenstorf, R. Larsson, S. Lars and T. Andersson The Kinetics of the Dissociation Reaction of Ferricenium Tri-iodine in Ben- zene Solution S. R. Logan and M. R. Welsh Gas Sensitivity of Polypyrrole Films to NO, T. Hanawa, S. Kuwabata and H. Yoneyama Determination of the Surface Coverage of Oxidic Supports by Oxidic and Non-oxidic Supported Phases by using Potentiometric Titration and Electrophoretic Mobility Data. A Study of the Fe,O,/Al,O, Supported Catalysts An Infrared Spectroscopic Study of Anatase Properties. Part 6.-Surface Hydration and Strong Lewis Acidity of Pure Sulphate-doped Preparations C.Morterra Vibrational Spectra of Potassium trans-4-Hexenoate and Conformational Change on Micellization H. Okabayashi, K. Tsukarnoto, K. Ohshirna, K. Taga and E. Nishio Solutions of Organic Solutes. Part 3.-Compression and Structure J. V. Ley endekkers Adsorption of Benzene and its Derivatives on a Zinc Oxide Surface M. Nagao and K. Matsuoka Basicity of Water in Organic Solvents using the 1,4,8,11 -Tetramethyl- 1,4, 8 , l l -Tetra-azacyclotetradecane Nickel(r1) Cation as a Probe of Electron- pair Acceptance in Nitromethane, Propane- 1,2-diol Carbonate and Acetone S. Yarnasaki, E. Iwamoto and T. Kumamuru Oxidation of Chloride to Chlorine by Cerium(1v) Ions mediated by a Microheterogeneous Redox Catalyst Structure and Reactivity of Zinc-Chromium Mixed Oxides. Part 2.-Study of the Surface Reactivity by Temperature-programmed Desorption of Methanol F.Trifiro, L. Mintchev, G. Busca, A. Vaccari and A. Riva X-Ray Absorption (EXAFS/XANES) Study of Supported Vanadium Oxide Catalysts. Structure of Surface Vanadium Oxide Species on Silica and y- Alumina at a Low Level of Vanadium Loading T. Tanaka, H. Yamashita, R. Tsuchitani, T. Funabiki and S. Yoshida Transference Number Measurements of Copper(x) Perchlorate in Binary Mixtures of Acetonitrile with Water, Methanol, Acetone and N,N- Dimethylformamide at 25 "C D. S. Gill, K. S. Arora, J. Tewari and B. Singh L. Vordonis, C. Kordulis and A. Lycourghiotis A. Mills and A. Cook xliTHE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY SYMPOSIUM No. 23 Molecular Vibrations University of Reading, 15-16 December 1987 Organising Committee: Professor I.M. Mills (Chairman) Dr J. E. Baggott Professor A. D. Buckingham Dr M. S. Child Dr N. C. Handy Dr B. J. Howard The Symposium will focus on recent advances in our understanding of the vibrations of polyatomic molecules. The topics to be discussed will include force field determinations by both ab initio and experimental methods, anharmonic effects in overtone spectroscopy, local modes and anharmonic resonances, intramolecular vibrational relaxation, and the frontier with molecular dynamics and reaction kinetics. The programme and application form may be obtained from: Mrs. Y. A. Fish, The Royal Society of Chemistry, Burlington House, London W1V OBN THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY GENERAL DISCUSSION No.85 Solvat ion University of Durham, 28-30 March 1988 Organising Committee: Professor M. C. R. Symons (Chairman) Professor J. S. Rowlinson Professor A. K. Covington Dr I. R. McDonald The purpose of the Discussion is to compare solvation of ionic and non-ionicspecies in the gas phase and in matrices with corresponding solvation in the bulk liquid phase. The aim will be to confront theory Gith experiment and to consider the application of these concepts to relaxation and solvolytic processes. Topics to be covered are: clusters, (c) Gas phase ionic clusters, (d) Liquid phase ionic solutions, (e) Dynamic processes including solvolysis. Speakers include: H. L. Friedman, B. J. Howard, M. J. Henchman, S. Tomoda, 0. Kajimoto, M. H. Abraham, Yu Ya Efimov, J.L. Finney, P. Suppan, J. P. Devlin, D. W. James, G. W. Neilson, T. Clark, M. L. Klein, J. T. Hynes, G. A. Kenney-Wallace, G. R. Fleming, M. J. Blandamer and D. Chandler. The preliminary programme may be obtained from: Mr. Y. A. Fish, The Royal Society of Chemistry, Burlington House, Lendon W1V OBN. +? Dr J. Yarwood Dr A. D. Pethybridge Professor W. A. P. Luck Dr D. A. Young (a) Gas phase non-ionic clusters, (b) Liquid phase non-ionic (xlii)THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY GENERAL DISCUSSION No. 86 Spectroscopy at Low Temperatures University of Exeter, 13-15 September 1988 Organising Committee: Professor A. C. Legon (Chairman) Dr P. B. Davies Dr B. J. Howard Dr P. R. R. Langridge-Smith Dr R. N. Perutz Dr M. Poliakoff The Discussion will focus on recent developments in spectroscopy of transient species (ions, radicals, clusters and complexes) in matrices or free jet expansions.The aim of the meeting is to bring together scientists interested in similar problems but viewed from the perspective of different environments. Further information may be obtained from: Professor A. C. Legon, Department of Chemistry, University of Exeter, Exeter EX4 4QD. THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY WITH THE ASSOCIAZIONE ITALIANA DI CHIMICA FISICA, DIVISION DE CHlMlE PHYSIQUE OF THE SOCIETE FRANCAISE DE CHlMlE AND DEUTSCHE BUNSEN GESELLSCHAFT FUR PHYSIKALISCHE CHEMIE JOINT MEETING Structure and Reactivity of Surfaces Centro Congressi, Trieste, Italy, 13-16 September 1988 Organising Committee: M.Che V.Ponec F. S. Stone G. Ertl R. Rosei A. Zecchina The conference will cover surface reactivity and characterization by physical methods: (i) Metals (both in single crystal and dispersed form) (ii) Insulators and semiconductors (oxides, sulphides, halides, both in single crystal and dispersed forms) (iii) Mixed systems (with special emphasis on metal-support interaction) The meeting aims to stimulate the comparison between the surface properties of dispersed and supported solids and the properties of single crystals, as well as the comparison and the joint use of chemical and physical methods. Further information may be obtained from: Professor C. Morterra, lnstituto di Chimica Fisica, Corso Massimo D'Azeglio 48, 10125 Torino, Italy. (x 1 i i i )THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY SYMPOSIUM Orientation and Polarization Effects in Reactive Collisions To be held at the Physikzentrum, Bad Honnef, West Germany, 12-14 December 1988 Organising Committee: Dr S.Stolte Professor R. N. Dixon Professor J. P. Simons Dr K. Burnett Professor H. Loesch Professor R. A. Levine The Symposium will focus on the study of vector properties in reaction dynamics and photodissociation rather than the more traditional scalar quantities such as energy disposal, integral cross-sections and branching ratios. Experimental and theoretical advances have now reached the stage where studies of Dynamical Stereochemistry can begin to map the anisotropy of chemical interactions. The Symposium will provide an impetus to the development of 3-D theories of reaction dynamics and assess the quality and scope of the experiments that are providing this impetus.Contributions for consideration by the Organising Committee are invited in the following areas: (A) Collisions of oriented or rotationally aligned molecular reagents (6) Collisions of orbitally aligned atomic reagents (C) Photoinitiated 'collisions' in van der Waals complexes (D) Polarisation of the products of full and half-collisional processes Further information may be obtained from: Professor J. P. Simons, Department of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD THE FARADAY DIVISION OF THE ROYAL SOCIETY OF CHEMISTRY GENERAL DISCUSSION No. 87 Catalysis by Well Characterised Materials University of Liverpool, 11-13 April 1989 Organ ising Committee : Professor R. W. Joyner (Chairman) Professor A. K. Cheetham Professor F. S. Stone The understanding of heterogeneous catalysis is an important academic activity, which compliments industry's continuing search for novel and more efficient catalytic processes. The emergence of relevant, in particular in sifu techniques and new developments of well established experimental approaches to catalyst characterisation are making a very significant impact on our knowledge of catalyst composition, structure, morphology and their inter-relationships. Well characterised catalysts, which will be the subject of the Faraday Discussion, include single-crystal surfaces, whether of metals, oxides or sulphides; crystalline microporous solids, such as zeolites and clays, and appropriate industrial catalysts. The elucidation of structure/function relationships and catalytic mechanism will be important aspects of the scientific programme. Contributions describing novel methods for synthesising well characterised catalysts and also reporting important advances in characterisation techniques will also be welcome. Contributions for consideration by the Organising Committee are invited and abstracts of about 300 words should be sent by 31 May 1988 to: Professor R. W. Joyner, Leverhulme Centre for Innovative Catalysis, Department of Inorganic, Physical and Industrial Chemistry, University of Liverpool, Grove Street, P. 0. Box 147, Liverpool L69 3BX. Full papers for publication in the Discussion volume will be required by December 1988. Dr. K. C. Waugh Professor P. B. Wells (xliv)FARADAY DIVISION INFORMAL AND GROUP MEETINGS Electrochemistry Group with the Electroanalytical Group Chemical Sensors To be held in London on 9-10 December 1987 Further information from Dr S. P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GL13 9PB Polar Solids Group A.G.M. and Group Meeting To be held at the University of Birmingham on 15-16 December 1987 Further information from Dr C. Greaves, Department of Chemistry, University of Birmingham, PO Box 363, Birmingham 815 2TT Electrochemistry Group with the Society of Chemical Industry Electrosynthesis To be held at the University of York on 15-17 December 1987 Further information from Dr S. P. Tyfield. Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GL13 9PB Colloid and Interface Science Group with the Society of Chemical Industry The Preparation of Colloid Particulates and the Annual General Meeting To be held at the Society of Chemical Industry, Belgrave Square, London on 16 December 1987 Further information from Dr R. Buscall, ICI PIC, Corporate Colloid Laboratory, PO Box 11, The Heath, Runcorn, Cheshire WA7 4QE High Resolution Spectroscopy Group with CCP6 Spectroscopy and Dynamics of highly Excited States of Molecules To be held at the University of Reading on 16-18 December 1987 Further information from Professor I. M. Mills, Department of Chemistry, University of Reading, Whiteknights, Reading RG6 2AD Neutron Scattering Group Scattering from Disordered Systems To be held at the University of Bristol on 16-18 December 1987 Further information from Dr G. W. Neilson. H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL Electrochemistry Group Electrochemistry/Surface Science: Must the Relationship remain Platonic? To be held at the University of Southampton on 6-7 January 1988 Further information from Dr S. P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GL13 9PBElectrochemistry Group Workshop on Electrochemical Techniques and Instruments To be held at the University of Warwick on 6-7 January 1988 Further information from Dr P. N. Bartlett, Department of Chemistry, University of Warwick, Coventry CV4 7AL Surface Reactivity and Catalysis Group with the Process Technology Group and the Institute of Chemical Engineers Opportunities for Innovation in the Application of Catalysis To be held at Queen Mary College, London on 6-7 January 1988 Further information from Professor J. Pritchard, Queen Mary College, London Division with the Institute of Mathematics and its Applications Mathematical Modelling of Semiconductor Devices and Processes To be held at the University of Loughborough on 7-8 January 1988 Further information from the Institute of Mathematics, Maitland House, Warrior Square, Southend-on-Sea SS1 2JY Division London Symposium: Modern Electrochemical Systems To be held at Imperial College, London on 12 January 1988 Further information from MrsY. A. Fish, Royal Society of Chemistry, Burlington House, London WIV OBN Polymer Physics Group with the 3Ps Group Plastics, Packaging and Printing To be held at the Institute of Physics, 47 Belgrave Square, London on 18 February 1988 Further information from Dr M. Richardson, National Physical Laboratory, Teddington, Middlesex Tw11 OLW Theoretical Chemistry Group Postgraduate Students' Meeting To be held at University College, London on 2 March 1988 Further information from Dr G. Doggett, Department of Chemistry, University of York, York ~ ~~ Colloid and Interface Science Group with The Society of Chemical Industry and British Radio frequency Spectrossop y Group Spectroscopy in Colloid Science To be held at the University of Bristol on 5-7 April 1988 Further information from Dr R. Buscall, ICI Corporate Colloid Science Group, PO Box 11, The Heath, Runcorn WA7 4QE Annual Congress: Division with Electrochemistry Group Solid State Materials in Electrochemistry To be held at the University of Kent, Canterbury on 12-1 5 April 1988 Further information from Dr J. F. Gibson, Royal Society of Chemistry, Burlington House, London W1V OBN Electrochemistry Group with The Society of Chemical Industry Electrolytic Bubbles To be held at Imperial College, London on 31 May 1988 Further information from Professor W. J. Albery, Department of Chemistry, Imperial College of Science and Technology, South Kensington, London SW7 2AY ~ ~ Electrochemistry Group with The Society of Chemical Industry Chlorine Symposium To be held at the Tara Hotel, London on 1-3 June 1988 Further information from Dr S. P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GL13 9BP Gas Kinetics Group Xth International Symposium on Gas Kinetics To be held at University College, Swansea on 24-29 July 1988 Further information from Dr G. Hancock, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 302 (xlvi)

ISSN:0300-9599    

DOI:10.1039/F198783BA001

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

Contents 3663 3669 3675 3683 3693 370 1 3709 3717 3725 3737 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(r1) IN,]-Macrocyclic Complexes. A Means of Breaking the Co-C Bond in B12 Co-enzyme M. Green, J. Daniels and L. M. Engelhardt The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach V. Malatesta, F. Morazzoni, L. Pellicciari-Bollini and R. Scotti Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution. Part 2.-Rifamycins R. Basosi, R. Pogni, E. Tiezzi, W. E. Antholine and L. C. Moscinsky An Electron Spin Resonance Investigation of the Nature of the Complexes formed between Copper(I1) and Glycylhistidine D. B. McPhail and B. A. Goodman A Vibronic Coupling Approach for the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins M.Bacci and S. Cannistr aro The Electron Spin Resonance Spectrum of Al[C,H,] in Hydrocarbon Matrices J. A. Howard, B. Mile, J. S. Tse and H. Morris N; and (CN); Spin-Lattice Relaxation in KCN Crystals H. J. Kalinowski and L. C. Scavarda do Carmo Single-crystal Proton ENDOR of the SO, Centre in y-Irradiated Sulphamic Acid N. M. Atherton, C. Oliva, E. J. Oliver and D. M. Wylie Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice 1,. Part 1.-The 0- Radicals Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals J. Bednarek and A. Plonka J. Bednarek and A. PlonkaContents 3663 3669 3675 3683 3693 370 1 3709 3717 3725 3737 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(r1) IN,]-Macrocyclic Complexes.A Means of Breaking the Co-C Bond in B12 Co-enzyme M. Green, J. Daniels and L. M. Engelhardt The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach V. Malatesta, F. Morazzoni, L. Pellicciari-Bollini and R. Scotti Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution. Part 2.-Rifamycins R. Basosi, R. Pogni, E. Tiezzi, W. E. Antholine and L. C. Moscinsky An Electron Spin Resonance Investigation of the Nature of the Complexes formed between Copper(I1) and Glycylhistidine D. B. McPhail and B. A. Goodman A Vibronic Coupling Approach for the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins M. Bacci and S. Cannistr aro The Electron Spin Resonance Spectrum of Al[C,H,] in Hydrocarbon Matrices J. A. Howard, B. Mile, J. S. Tse and H. Morris N; and (CN); Spin-Lattice Relaxation in KCN Crystals H. J. Kalinowski and L. C. Scavarda do Carmo Single-crystal Proton ENDOR of the SO, Centre in y-Irradiated Sulphamic Acid N. M. Atherton, C. Oliva, E. J. Oliver and D. M. Wylie Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice 1,. Part 1.-The 0- Radicals Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals J. Bednarek and A. Plonka J. Bednarek and A. Plonka

ISSN:0300-9599    

DOI:10.1039/F198783FX045

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

Electrochemistry Group Workshop on Electrochemical Techniques and Instruments To be held at the University of Warwick on 6-7 January 1988 Further information from Dr P. N. Bartlett, Department of Chemistry, University of Warwick, Coventry CV4 7AL Surface Reactivity and Catalysis Group with the Process Technology Group and the Institute of Chemical Engineers Opportunities for Innovation in the Application of Catalysis To be held at Queen Mary College, London on 6-7 January 1988 Further information from Professor J. Pritchard, Queen Mary College, London Division with the Institute of Mathematics and its Applications Mathematical Modelling of Semiconductor Devices and Processes To be held at the University of Loughborough on 7-8 January 1988 Further information from the Institute of Mathematics, Maitland House, Warrior Square, Southend-on-Sea SS1 2JY Division London Symposium: Modern Electrochemical Systems To be held at Imperial College, London on 12 January 1988 Further information from Mrs Y.A. Fish, Royal Society of Chemistry, Burlington House, London W1V OBN Polymer Physics Group with the 3Ps Group Plastics, Packaging and Printing To be held at the Institute of Physics, 47 Belgrave Square, London on 18 February 1988 Further information from Dr M. Richardson, National Physical Laboratory, Teddington, Middlesex l w 1 1 OLW Theoretical Chemistry Group Postgraduate Students’ Meeting To be held at University College, London on 2 March 1988 Further information from Dr G. Doggett, Department of Chemistry, University of York, York Colloid and Interface Science Group with The Society of Chemical Industry and British Radio frequency Spectroscopy Group Spectroscopy in Colloid Science To be held at the University of Bristol on 5-7 April 1988 Further information from Dr R. Buscall, ICI Corporate Colloid Science Group, PO Box 11, The Heath, Runcorn WA7 40E Annual Congress: Division with Electrochemistry Group Solid State Materials in Electrochemistry To be held at the University of Kent, Canterbury on 12-15 April 1988 Further information from Dr J.F. Gibson, Royal Society of Chemistry, Burlington House, London W1V OBN Electrochemistry Group with The Society of Chemical Industry Electrolytic Bubbles To be held at Imperial College, London on 31 May 1988 Further information from Professor W. J. Albery, Department of Chemistry, Imperial College of Science and Technology, South Kensington, London SW7 2AY Electrochemistry Group with The Society of Chemical Industry Chlorine Symposium To be held at the Tara Hotel, London on 1-3 June 1988 Further information from Dr S.P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GLI 3 9BP Gas Kinetics Group Xth International Symposium on Gas Kinetics To be held at University College, Swansea on 24-29 July 1988 Further information from Dr G. Hancock, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 302 (xiii)Electrochemistry Group Workshop on Electrochemical Techniques and Instruments To be held at the University of Warwick on 6-7 January 1988 Further information from Dr P.N. Bartlett, Department of Chemistry, University of Warwick, Coventry CV4 7AL Surface Reactivity and Catalysis Group with the Process Technology Group and the Institute of Chemical Engineers Opportunities for Innovation in the Application of Catalysis To be held at Queen Mary College, London on 6-7 January 1988 Further information from Professor J. Pritchard, Queen Mary College, London Division with the Institute of Mathematics and its Applications Mathematical Modelling of Semiconductor Devices and Processes To be held at the University of Loughborough on 7-8 January 1988 Further information from the Institute of Mathematics, Maitland House, Warrior Square, Southend-on-Sea SS1 2JY Division London Symposium: Modern Electrochemical Systems To be held at Imperial College, London on 12 January 1988 Further information from Mrs Y.A. Fish, Royal Society of Chemistry, Burlington House, London W1V OBN Polymer Physics Group with the 3Ps Group Plastics, Packaging and Printing To be held at the Institute of Physics, 47 Belgrave Square, London on 18 February 1988 Further information from Dr M. Richardson, National Physical Laboratory, Teddington, Middlesex l w 1 1 OLW Theoretical Chemistry Group Postgraduate Students’ Meeting To be held at University College, London on 2 March 1988 Further information from Dr G. Doggett, Department of Chemistry, University of York, York Colloid and Interface Science Group with The Society of Chemical Industry and British Radio frequency Spectroscopy Group Spectroscopy in Colloid Science To be held at the University of Bristol on 5-7 April 1988 Further information from Dr R.Buscall, ICI Corporate Colloid Science Group, PO Box 11, The Heath, Runcorn WA7 40E Annual Congress: Division with Electrochemistry Group Solid State Materials in Electrochemistry To be held at the University of Kent, Canterbury on 12-15 April 1988 Further information from Dr J. F. Gibson, Royal Society of Chemistry, Burlington House, London W1V OBN Electrochemistry Group with The Society of Chemical Industry Electrolytic Bubbles To be held at Imperial College, London on 31 May 1988 Further information from Professor W. J. Albery, Department of Chemistry, Imperial College of Science and Technology, South Kensington, London SW7 2AY Electrochemistry Group with The Society of Chemical Industry Chlorine Symposium To be held at the Tara Hotel, London on 1-3 June 1988 Further information from Dr S. P. Tyfield, Central Electricity Generating Board, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire GLI 3 9BP Gas Kinetics Group Xth International Symposium on Gas Kinetics To be held at University College, Swansea on 24-29 July 1988 Further information from Dr G. Hancock, Physical Chemistry Laboratory, South Parks Road, Oxford OX1 302 (xiii)

ISSN:0300-9599    

DOI:10.1039/F198783BX047

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

ISSN 0300-9599 JCFTAR 83(12) 3469-3747 (1 987) 3469 3493 3505 3513 3527 3535 354 1 3 549 3565 3575 3587 3603 361 3 3619 3627 3635 3653 JOURNAL OF THE CHEMICAL SOCIETY Faraday Transactions I Physical Chemistry in Condensed Phases CONTENTS This issue contains papers given at the 20th Annual E.S.R. Conference at York during March-April 1987, including the second Bruker Lecture by Professor K. Mobius. Multiple Resonances involving Electron Spin Resonance, Nuclear Magnetic Resonance and Optical Transitions: More than Just a Game? K. Mobius MAGRES: A General Program for Electron Spin Resonance, ENDOR and ESEEM C. P. Keijzers, E. J. Reijerse, P. Stam, M. F. Dumont and M. C. M. Gribnau Interpretation of Electron Spin-echo Modulation for Copper(I1) Complexes in Crystalline Powders An Electron Spin Resonance Study of Complexes of Oxovanadium(1v) with Simple Dicarboxylic Acids Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalco- genides R.E. Benfield, P. P. Edwards and A. M. Stacy The Electron Spin Resonance Spectra of CpCr(CO), and CpCr(CO),P(C,H,), in Single Crystals of their Mn Analogues J. R. Morton, K. F. Preston, N. A. Cooley, M. C. Baird, P. J. Krusic and S. J. McLain An Electron Spin Resonance Study of Rutile and Anatase Titanium Dioxide Polycrystalline Powders treated with Transition-metal Ions A. Amorelli, J. C. Evans, C. C. Rowlands and T. A. Egerton Electron Spin Resonance and Electronic Spectroscopy of Low-spin Man- ganese(r1) Complexes (C,R,)(CO),(L)Mn with L = Hydrazido( 1-), Arylamido, Anionic Nitrile and Purine-type Ligands An Electron Spin Resonance Study of Isomerism in a Coo Acetylene n- Complex Binding of Paramagnetic Ions in Ionomers.Cu2+ and Ti3+ in Nafion Membranes S. Schlick and M. G. Alonso-Amigo Spectromagnetic Evidence for Spatial Correlation of Copper Centres in Phosphate Glasses and its Effect on the Charge-transport Processes D. Narducci, C. M. Mari, S. Pizzini and F. Morazzoni Electron Spin Resonance Spectra of a Ferromagnetic Alternating Spin Chain ( S , = i, S = i) The Electron Spin Resonance Powder Spectrum of RerV in TiO, E. J. Reijerse, P. Stam, C. P. Keijzers, M. Valigi and D. Cordischi Interaction of Carbon Monoxide with Ru/y-Al,O,. An Electron Spin Resonance Investigation M. G. Cattania, A. Gervasini, F. Morazzoni, R. Scotti and D. Strumolo Oxovanadium(1v) Complexes of Cysteine characterized by Electron Spin Resonance Spectroscopy Studies of the Manganese Site of Photosystem I1 by Electron Spin Resonance Spectroscopy J.C. de Paula, W. F. Beck, A-F. Miller, R. B. Wilson and G. W. Brudvig Electron Capture by Ferrl and (FeO,) Centres in Haemoglobin, and the Absence of Subsequent Electron Transfer from (Fe0,)- Centres to Fe"'. An Electron Spin Resonance Study M. C. R. Symons and F. A. Taiwo M. W. Anderson and L. Kevan D. B. McPhail and B. A. Goodman R. Gross and W. Kaim J. A. DeGray, Q. Meng and P. H. Rieger A. Caneschi, D. Gatteschi, C. Zanchini and P. Rey D. B. McPhail and B. A. Goodman 115 FAR 1Contents 3663 3669 3675 3683 3693 370 1 3709 3717 3725 3737 Normal and Abnormal Electron Spin Resonance Spectra of Low-spin Cobalt(r1) IN,]-Macrocyclic Complexes.A Means of Breaking the Co-C Bond in B12 Co-enzyme M. Green, J. Daniels and L. M. Engelhardt The Interaction between Superoxide Dismutase and Doxorubicin. An Electron Spin Resonance Approach V. Malatesta, F. Morazzoni, L. Pellicciari-Bollini and R. Scotti Biomolecular Dynamics and Electron Spin Resonance Spectra of Copper Complexes of Antitumour Agents in Solution. Part 2.-Rifamycins R. Basosi, R. Pogni, E. Tiezzi, W. E. Antholine and L. C. Moscinsky An Electron Spin Resonance Investigation of the Nature of the Complexes formed between Copper(I1) and Glycylhistidine D. B. McPhail and B. A. Goodman A Vibronic Coupling Approach for the Interpretation of the g-Value Temperature Dependence in Type-I Copper Proteins M. Bacci and S. Cannistr aro The Electron Spin Resonance Spectrum of Al[C,H,] in Hydrocarbon Matrices J. A. Howard, B. Mile, J. S. Tse and H. Morris N; and (CN); Spin-Lattice Relaxation in KCN Crystals H. J. Kalinowski and L. C. Scavarda do Carmo Single-crystal Proton ENDOR of the SO, Centre in y-Irradiated Sulphamic Acid N. M. Atherton, C. Oliva, E. J. Oliver and D. M. Wylie Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice 1,. Part 1.-The 0- Radicals Single-crystal Electron Spin Resonance Studies on Radiation-produced Species in Ice I,. Part 2.-The HO, Radicals J. Bednarek and A. Plonka J. Bednarek and A. Plonka

ISSN:0300-9599    

DOI:10.1039/F198783FP161

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. SOC., Faraday Trans. I, 1987, 83 (12), 3469-3492 Multiple Resonances involving Electron Spin Resonance, Nuclear Magnetic Resonance and Optical Transitions : More than Just a Game?? Klaus Mobius Free University of Berlin, Department of Physics, Arnimallee 14, 0-1000 Berlin 33, Federal Republic of Germany The detection of hyperfine couplings in large and low-symmetry molecules is often hampered by problems of sensitivity and/or resolution. In such situations solutions to the problem are offered by simultaneously driving n.m.r., e.s.r. and optical transitions leading to well characterized elec- tron-nuclear double and triple resonance (ENDOR, TRIPLE) and optically detected quadrupole resonance (ODNQR) spectra. The basic strategies of these multiple resonance techniques are discussed, together with applications to photosynthetic systems and spin-polarized aromatic molecules.It is a great honour to give this second Bruker Lecture of the Royal Society of Chemistry, and I am deeply indebted to the Committee of the Electron Spin Resonance Group of the Royal Society for having selected me as their lecturer. In this lecture, I summarize our recent work on the development of multiple magnetic resonance techniques and their applications for studying ground-state doublet and excited-state triplet molecules in photochemistry and photobiology. The research I am going to report on has been carried out together with numerous undergraduate and graduate students, postdoctoral collaborators and visitors; to all of them I express my gratitude . The lecture is divided into three parts.(i) Steady-state ENDOR and TRIPLE resonance spectroscopy on long-lived radicals in solution (lifetime z % spin-lattice relaxation time q). Examples will be presented from the field of bacterial photosynthesis. (ii) CIDEP-enhanced ENDOR and TRIPLE resonance on electron spin-polarized transient radicals in solution (z 5 q). As examples systems with net and multiplet effect polarization will be described. (iii) ODMR and ODNQR in zero magnetic field on electron spin-polarized triplet-state molecules in frozen glasses. Aza-aromatics will be discussed as examples. As a general strategy of multiple resonance spectroscopy two goals can be formulated. (i) Improvement of spectral resolution. This is achieved by elimination of redundancy in the spectrum, i.e.more than one selection rule is introduced by applying more than one electromagnetic radiation field to the system, thereby restricting its spectral response. A typical example for this strategy is ENDOR (electron-nuclear double resonance), where the pioneering work was done by Feherl in the solid state, by Hyde and Maki' in solution and by Freed,3 who developed the theoretical understanding of multiple resonances in solution.. (ii) Improvement of spectral sensitivity. This is achieved by quantum transformation from the low-frequency domain, where the spin transitions occur, to the high-frequency domain, where the absorbed energy is detected. A typical 7 Second Bruker Lecture of the Royal Society of Chemistry given at the Nineteenth Annual International E.S.R.Conference held at the University of York, 30 March-3 April, 1987. 3469 115-23470 Multiple Resonances involving E.S. R., N.M.R. and Optical Transitions example for this stfategy is ODMR (optically detected magnetic resonance), where the pioneering work in zero field was done by Schmidt and van der W a a l ~ . ~ Multiple-resonance experiments can become quite complex in their theoretical analysis, and it is often desirable, as a first approach, not to go through the full treatment of a rigorous theory, but rather to have simple models at hand by which one can gain a feeling of the potentials and limitations of these techniques. Such models are based on rate equations for level populations, and turn out to be very useful in visualizing how spin populations can be shuffled around in intelligent ways.Steady-state ENDORlTRIPLE Studies of Long-lived Radicals in Solution Principles In photoreactions e.s.r. plays a major role as a spectroscopic tool for the characterization of radicals, since (unlike the case in optical spectroscopy) details of the molecular structure can be derived from resolved hyperfine splittings. There are, however, important photochemical reactions, e.g. the primary reactions in photosynthesis, where the radicals involved are so large or so asymmetrical in their structure that the number of e.s.r. lines runs into thousands, merging together into inhomogeneously broadened bands with little or no resolvable hyperfine information. If we shake the spin system with a second radiation field, the n.m.r.r.f. field in an ENDOR experiment, we introduce a second selection rule and out of the line jungle hyperfine structure emerges. An aesthetically pleasing example of the resolving power of ENDOR is given in fig. 1, where the e.s.r. and ENDOR spectra of the radical cation of bacteriochlorophyll a in solution are compared. In this radical, which plays an important role in bacterial photosynthesis, the unpaired electron is delocalized in the n-electron system and interacts with numerous a-, D- and y-type protons (one, two and three bonds away from the n carbon skeleton) with 14N and "Mg nuclei. The complexity of the hyperfine interactions leads to a single inhomogeneously broadened Gaussian-envelope e.s.r. line at g = 2.0026. The ENDOR spectrum, on the other hand, shows well resolved hyperfine line^.^.^ In the 'H ENDOR range 11 line pairs can be discerned centred around the Larmor frequency v,, of the proton (ca.14 MHz at X band) which can be assigned to a, p and y protons. Additional 14N ENDOR lines occur at lower frequencies near the nitrogen Lannor frequency (ca. 1 MHz), and in isotope-enriched samples "Mg lines can also be dete~ted.~ According to the ENDOR resonance condition v: = Iv,,-tiail (1) the isotropic hyperfine coupling constants ai can be obtained directly from the line positions. Any group of equivalent nuclei, no matter what their resultant spin, thus contributes only two lines to the ENDOR spectrum. In contrast to this additive increase of lines with increasing number of groups, the number of lines in an e.s.r.spectrum increases in a multiplicative way, making ENDOR the method of choice for large and low-symmetry radicals. In an ENDOR experiment one adjusts the magnetic-field value to an e.s.r. line, saturates it and simultaneously sweeps a saturating n.m.r. r.f. field through the resonance region of the various nuclei. Because in solution the spin-lattice relaxation times of the electron and nuclear spins are very short (typically lop5 s), one needs considerable field strengths of the electromagnetic radiation fields to achieve saturation. In our experimental arrangement with a TM,,, microwave cavity with an internal n.m.r. coil wound around the sample-containing Dewar, typical power requirements are 0.01-0.2 W in the microwave region and 0.1-1 kW in the r.f.region.* We have extended ENDOR to electron-nuclear-nuclear triple resonance (TRIPLE) experiments with the following aims.347 1 270 K I L N la mn 8a la 5a Jr I I I I I I I I I I I I I I I I I I I I I I I 1 3 5 7 9 11 13 15 17 19 21 23 I ENDOR frequency/MHz K . Mobius Fig. 1. (a) E.s.r. and (b) ENDOR spectra of the bacteriochlorophyll a (c) cation radical in CH,Cl,-CH,OH solution. The signs at both the 14N and ‘H lines indicate the signs of correspond- ing hyperfine coupling constants ; they were determined from General TRIPLE resonance. Assignments of hyperfine coupling constants to specific molecular positions are based on specific deuteration, temperature studies of line intensities, comparison with related radicals, and results of advanced molecular-orbital theories.The usual labelling scheme is used in the structural formula, the z, /I and y positions should not be confused with a-, /I- and y-type protons mentioned in the text. In ’ Special TRIPLE’,S~10 which applies to only one group of equivalent nuclei, the spectral sensitivity is considerably improved. Furthermore, the lines are generally narrower, and their intensity ratios, in contrast to ENDOR, approximately reflect the number of nuclei involved in the transition. This yields important information for assigning the hyperfine coupling constants to individual molecular positions. In a Special TRIPLE experiment two r.f. fields are frequency-swept symmetrically about v,, while the e.s.r. transition is saturated. In ‘General TRIPLE’,lO.ll which applies to more than one group of nuclei, relative signs of hyperfine coupling constants can be directly determined from characteristic intensity changes of the ENDOR lines occurring when one n.m.r.transition is additionally pumped while sweeping the second r.f. field through the ENDOR region.3472 Multiple Resonances involving E.S. R., N.M. R. and Optical Transitions Such sign information is very important for assigning hyperfine coupling constants to different types of nuclei. The signs on the ENDOR lines in fig. 1 have been determined in this way. A profound theoretical treatment of steady-state multiple-resonance experiments on radicals tumbling rapidly in isotropic solution has been carried out by Freed and coworkers who, in a series of papers,12-16 used the density-matrix method to calculate line positions, amplitudes and shapes of multiresonance spectra in the Redfield approximation :" For such experiments the spin Hamiltonian is of the form (2) (3) I(X,(t))IzRfi-' 6 X(t) = X o + X,(t) + t(t) where Z0 is the time-independent part, giving the zero-order energy levels and transition frequencies, A?'( t ) contains energy terms randomly time-modulated by the Brownian tumbling motion (rotational correlation time zR), thereby causing relaxation, and t( t ) represents the interactions of all electron and nuclear spins with the external coherent radiation fields.Regarding the behaviour of ENDOR and TRIPLE spectra, the term A?,(?) is of primary interest, as it determines the magnitude of all spin-lattice relaxation rates WaD and linewidth parameters (1/T2),8 between any two levels a and p of the spin system.Brownian rotation of a radical in solution causes the following contributions to X,(t): (i) a spin-rotation interaction, resulting in electronic relaxation parameters We and G2 ; (ii) an electron Zeeman interaction, resulting in We and q:; (iii) an electron-nuclear dipole interaction, resulting in electronic, nuclear and cross-relaxation parameters We, Wn, Wxl, Wx2, T;,k', ci, q:, and c:2; (iv) a nuclear quadrupole interaction, resulting in Wn and ci. For organic radicals terms (i) and (iii) are normally dominant in Xl(t). On the basis of Freed's theory, but introducing certain simplifying assumptions which are realistic for most organic radicals, a general computer program was developed in our research group," suitable for any C.W.magnetic-resonance experiment with a maximum of two microwave and two r.f. radiation fields. The input data for a specific experiment consist of parameters derived from the Hamiltonians Xo, Xl(t) and 2(t), the output data contain the ENDOR or TRIPLE signal amplitudes and linewidths (actually the complete lineshapes of the resonance enhancement) and the optimum microwave and r.f. field strengths required for the radical in question at an optimum rotational correlation time. Such studies of ENDOR intensities of various nuclei in their specific molecular environment can now be performed in a systematic way,18+'9 and allow predictions to be made whether or not ENDOR-in-solution will be successful for a specific problem.A complete relaxation theory treatment of a multi-spin-multi-resonance project can become quite tedious, and one would therefore like to have simple models at hand by which the various situations for multiple spin-flipping experiments could be visualized. In the absence of r.f.-induced coherence ENDOR and TRIPLE en- hancements can be described by rate equations for spin level population redistributions under the influence of relaxation and induced transitions. These rate equations can be represented by electric network analogies2' when exact ' on-resonance ' conditions are assumed.8~10 In such a phenomenological description the ENDOR experiment, for instance, can be visualized by the creation of an alternative relaxation bypass for the pumped electron spins, which is opened by driving an n.m.r.transition and which competes with the direct We route. Special TRIPLE will increase the efficiency of this r.f.-induced relaxation bypass in such cases where a Wn bottleneck is included. Different relaxation networks are adequate for General TRIPLE experirnents,l0* l1 depending on the relative signs of the hyperfine coupling constants involved : a 'pyramid ' network for sign a, = sign a, and aK. Mobius 100 II 1 0. 3473 Fig. 2. TRIPLE amplification factor us. the ratio of electron and nuclear relaxation rates calculated for the relaxation networks of various multiple resonance experiments. In General TRIPLE the electric circuit analogies represent a tetrahedron or a pyramid depending on the relative signs of the hyperfine coupling constants.The curves shown are valid for induced n.m.r. rates 100 times larger than Wn. For details, see ref. (10). ( a ) pyramid, General TRIPLE (al, a, > 0), (b) ENDOR, (c) tetrahedron, General TRIPLE (a, > 0, a, < 0), ( d ) Special TRIPLE. ‘tetrahedron’ network for sign a, # sign a,. As is shown in fig. 2, both relaxation networks give drastically different amplifications of the ENDOR amplitude. In particular, for the frequently occurring case of a Wn bottleneck (We/ Wn % l), the Special TRIPLE experiment results in a considerably improved spectral sensitivity, and from well pronounced intensity changes in the General TRIPLE experiments relative signs of hyperfine coupling constants can easily be inferred. Examples : Primary Donor Radical Ions in Bacterial Photosynthesis We have applied the TRIPLE resonance techniques to the radical ions involved in bacterial photosynthesis both to in uitro systems, i.e. isolated chromophores, and to in vivo systems, i.e.chromophore-protein complexes of photosynthetic reaction centres. The chromophores which are embedded in the reaction centres of photosynthetic purple bacteria such as Rhodopseudomonas (Rps.) sphaeroides, Rhodospirillurn (R.) rubrum and Rps. viridis, are shown in fig. 3. Rps. sphaeroides and R. rubrum contain bac- teriochlorophyll a (BChl a) and bacteriopheophytin a (BPh a), whereas Rps. uiridis contains BChl b and BPh b. All our efforts in performing TRIPLE resonance on the in vitro and in uivo systems resulted in spectra with well resolved hyperfine structure, from which spin-density maps of the donor and acceptor radical ions could be d e r i ~ e d .~ - ~ g ~ ~ - ~ ~ The assignment of hyperfine coupling constants to molecular positions was achieved by Special and General TRIPLE, by temperature studies of the line intensities, by selective isotope labelling (2H, 15N and 25Mg) and, in some cases, by the results of sophisticated molecular-orbital calculations. By means of these molecular-orbital calculations information about the spatial3474 Multiple Resonances involving E.S.R., N.M.R. and Optical Transitions ' \' 8Nx BChl b \ \ \ 0 0 mena quin one ubiquinone R I phytyl: -CH2-CH=C-(CH )-CH-(CH ) -CH-(CH213-CH-CH I 2 3 1 2 3 I I 3 CH3 CH3 CH3 CH3 BChl a I C-H 3 R BPh a Fig.3. Structural formulae of typical chromophores in the reaction centre of photosynthetic bacteria such as Rps. sphaeroides [containing bacteriochlorophyll a (BChl a) and bacterio- pheophytin a (BPh a)]. Rps viridis bacteria contain BChl b (only the deviation from BChl a is shown). The side-chain R is phytyl in Rps. sphaeroides, but geranylgeranyl in R. rubrum. In the quinones the length (n) of the side-chain is n = 10 for Rps. sphaeroides and R. rubrum, but n = 9 for Rps. uiridis. structure of the donor and acceptor ions could be derived via a detailed analysis of the s-spin density distribution and via minimization of the total energy. The molecular-orbital theory for calculating total energies and spin and charge density distributions, is an INDO parametrized all-valence-electron restricted Har- tree-Fock SCF-MO method with subsequent perturbation treatment of spin-polar- ization effects (RHF-INDO/SP) which has been shown to be very powerful in handling large molecular With this molecular-orbital method s-spin densities were calculated and directly compared with experimental hyperfine coupling constants by use of charge- and geometry-independent atomic Fermi contact interaction parameters.In this procedure there is no need for 71-0 polarization Q factors, which always introduce an additional element of ambiguity. Fig. 4 gives the results of the s-spin density calculations for BChl a+ after partial geometry optimization with respect to total energy.31 For comparison the experimental s-spin densities are included in the figure (dotted), demonstrating that the agreement between theory and experiment is very satisfying, not only for the various protons but also for the nitrogens and the magnesium.This success encouraged us to apply the RHF-INDO/SP molecular-orbital method to analysis of the ENDOR/TRIPLE spectra of in vivo reaction centres under physiological conditions. The purpose of this study is to learn more about the three-dimensionalK. Mobius 3475 8 E P = P = 0.010 \ Fig. 4. Comparison of experimental (dotted lines) and calculated (RHF-INDO/SP method, solid lines) s-spin densities for the BChl a+ cation radical after partial geometry optimization by energy minimization. Their values are proportiona1 to the areas of the circles (p > 0) and squares (p < 0), respectively.Theoretical carbon and oxygen spin densities are omitted for reasons of clarity. For details, see ref. (31). structure of the primary donor, the ‘special pair’,32 in its cation doublet state and to compare our results with the recent X-ray structure data of the reaction centre of Rps. ~ i r i d i s ~ ~ with the primary donor in its neutral singlet ground state. The ultimate goal of these investigations is to contribute to the understanding of the relation between the spatial and electronic structure of the chromophore molecules in their specific protein environment and their function in the very fast and ‘diode’-like electron-transfer chain, which ensures the high quantum efficiency of the primary photosynthetic processes. As a brief reminder of the primary processes in bacterial photosynthesis, fig.5 indicates the first steps in the electron-transfer chain. As an example, the Rps. sphaeroides reaction centres are chosen. The sequence of events starts with singlet excitation of the primary donor D,, the P,,, which is the ‘special pair’ dimer of bacteriochlorophylls,32 with subsequent ultrafast primary charge separation. The primary acceptor, A,, is probably a bacteriopheophytin. In the next step stabilization3476 Multiple Resonances involving E.S.R., N.M.R. and Optical Transitions L A hu (870 nml Dl A1 A2 I Fig. 5. Primary electron-transfer steps after illumination of reaction centres of photosynthetic bacteria Rps. sphaeroides. The primary donor, D,, is the P,,, ‘special pair’ of 2 BChl a molecules, the primary and secondary acceptors, A , and A,, are BPh a and a quinone iron com- plex, respectively. The electron transfer half-lifetimes are averaged values from data recently pub- lished.’O9 ’ against charge recombination is achieved by passing the electron to the secondary acceptor, A,, which is a quinone iron complex. From there, further stabilization occurs to the extent that biochemical ‘dark’ reactions with energy conversion can proceed. The organization of the chromophores in the protein environment of the reaction centre is optimized by Nature to allow the forward reactions to be much faster than the wasteful back-reactions. As a consequence of this ‘ diode ’-like behaviour the quantum efficiency of the primary photo-oxidation of PS7,, almost reaches 100 % .3 4 7 3 5 The reaction centre of Rps. sphaeroides consists of three protein subunits L, M and H (light, medium and heavy) of total molecular weight of 73 000 incorporating, as primary reactants, four BChl a, two BPh a, two ubiquinones and one Fe2+ From the reaction centre of the bacterium Rps. uiridis, which is expected to have characteristic structural features in common with Rps. sphaeroides and other photosynthetic organisms, the first X-ray structure analysis at atomic resolution of a membrane protein was executed recently by Michel et al.33 Their results allowed the construction of an atomic model that includes the protein subunits and chromophores. The central membrane-bound part of the reaction centre consists of the protein subunits L and M incorporating four BChl b, two BPh b, one menaquinone, one ubiquinone (normally lost in the crystallization procedure), and one non-haeme iron.The H protein subunit is attached to this central LM complex on the cytoplasmic side of the membrane. The cytochrome protein (which is not bound to the reaction centre of Rps. sphaeroides) is attached to the periplasmic side and contains four haeme groups in a linear arrangement. The LM complex is the most interesting part of the reaction centre. The arrangement of the helices in the L and M subunits and chromophores shows approximate local C, symmetry about an axis perpendicular to the membrane planes and running through the pyrrole rings I of two BChl b molecules in close contact (the ‘special pair’ with face- to-face contact of rings I) and the iron.This twofold rotation symmetry is manifested by two structurally almost equivalent branches of chromophores, the L branch and the M branch, each containing the special pair (the primary donor in the electron-transfer chain), one accessory BChl b, one BPh 6 , and one quinone. The BChl components of theK. Mobius r-----l 3477 per ip I asm 7 membrane B,,Y,$$QCh' I QA oBph O B P h 200 ps 100 ps - QB cytoplasm Fig. 6. Structural arrangement of the chromophores in the reaction centres of Rps. viridis with the L, M, H and cytochrome protein The BChl and BPh abbreviations stand for bacteriochlorophyll b and bacteriopheophytin b, HE for haeme groups, Q, for menaquinone and Q, for ubiquinone. The electron-transfer half-lifetimes (kET)-l are averaged values from data recently published.70* 71 special pair start, while the quinones terminate, the sequence of prosthetic groups in the two branches; they are bridged by the iron at the symmetry axis.The spatial arrangement of the chromophores is depicted schematically in fig. 6, which also contains the electron-transfer half-lifetimes (kET)-' for the various steps. Among the many open questions concerning the primary processes, one observa- t i ~ n ~ ~ is particularly puzzling : that electron transfer proceeds predominantly via the L branch of the reaction centre in spite of the approximate C, symmetry of arrangement of chromophores, i.e. although the spatial and orientational ordering of the prosthetic groups in the L and M branches is almost identical. From an analysis of time-resolved delayed fluorescence of Rps.viridis reaction centres a branching ratio of the primary electron-transfer rates k,ET/kF w 6 was inferred. 37 The following questions thus arise. (i) What is responsible for the unidirectionality of the electron transfer along the L branch? (ii) Is this asymmetry in the electron-transfer rates already rooted in an asymmetric electron charge distribution in the dimer halves of the primary donor? (iii) Or does this asymmetry rather stem from different interactions between the pigment molecules and neighbouring amino acid residues of the L and M proteins? (iv) Or do both contributions occur together in a concerted effort? To answer these questions not only must the geometrical arrangement of the chromophores be known, but also it is clearly essential to understand the electronic structure of the primary donor in great detail, including possible perturbations from the protein environment.Access to such information cannot be obtained from an analysis of X-ray structure alone, but also requires high-resolution spectroscopic experiments, such as ENDOR/TRIPLE, with subsequent interpretation of the data by means of sophisticated theories.3478 Multiple Resonances involving E.S.R., N.M.R. and Optical Transitions I I I I I I I I I I I I CH3 la,5a I I I I I I I I I 1 + + ( b ) I ? I + ~ I I I I I I I I 0 1 2 3 4 5 6 7 8 frequency/MHz Fig. 7. Proton Special TRIPLE spectra of (a) BChl a+ at 255 K and (6) P&, of Rps. sphaeroides at 293 K (in H,O, illuminated). Signs of the hyperfine coupling constants were obtained from General TRIPLE, assignments are based on specific deuteration and molecular-orbital calculations.For details, see ref. (41). More than a decade ago Feher et ~ 1 . ~ ~ and Norris et al.39 had already tried to elucidate the structure of the primary donor by applying ENDOR at low temperature to in vitro BChl a+ and in vivo P&, looking for characteristic differences in the spectra of these compounds. They observed relatively broad ENDOR lines which they attributed to p- type protons. The respective values of the hyperfine coupling constants in the reaction- centre donor cations were approximately half as large as those observed in BChl a+, from which the authors concluded that the unpaired electron is shared between two BChl a molecules undergoing fast hopping on the timescale of an e.s.r./ENDOR experiment.There are obvious drawbacks of an ENDOR experiment at low temperatures : only a few broad lines from /? protons are detectable, but no lines form a protons and nitrogens. Furthermore, one would like to probe the reaction-centre structure under physiological conditions rather than at low temperature. As a logical consequence we have attempted ENDOR/TRIPLE-in-solution on the in situ illuminated protein complex of bacterial reaction centres from Rps. sphaeroides, R. rubrum and Rps. viridis in water at room temperature.23.27*30,40*41 Estimates of the rotational correlation time from the Einstein-Debye relation zR = Cff q/kT (where cff is the effective volume of the complex, is the viscosity of the solvent and T is theK.Mobius 3479 Table 1. Proton hyperfine coupling constants and their reduction factors of BChl a+ and Pi7o from Rps. sphaeroides R-26 a/MHz reduction factor, position BChl a+ Pi7,, aRChla+/aP;,o ~~ CH3 (1) 4.93 4.00 1.23 11.76 3.30 3.56 13.11 4.45 2.95 P-H CH3 (111) 9.62 5.60 1.72 13.47 8.60 1.57 16.35 9.50 1.72 B-H B-H) (11, IV) P-H ) (11, IV) All hyperfine data were obtained from ENDOR/TRIPLE in ~olution.~~ The assignment of hyperfine coupling constants to molecular positions was achieved by selective deuteration and General TRIPLE experiments. The roman numbers refer to the pyrrole rings in the bacteriochlorophyll systems (see fig. 3). absolute temperature) yield z, z 30 ns for the whole reaction centre complex of Rps.sphaeroides in water at 25 "C. Thus, the Redfield condition (2) is still valid for nuclei with small anisotropies in their hyperfine coupling constants ( 5 5 MHz), e.g. for the protons and nitrogens of the bacteriochlorophylls. From the reaction centres of all three organisms we obtained well resolved ENDOR/ TRIPLE spectra of the light-induced primary-donor cation radicals under physiological conditions, from which numerous hyperfine coupling constants, including their signs, could be deduced. In fig. 7 the Special TRIPLE spectra of BChl a+ and are depicted. When one compares the six reliably assigned proton hyperfine coupling constants of both systems (table 1) one sees that the corresponding values are indeed reduced, but not by a constant factor of 2, as proposed in a simple ' hopping-dimer ' model of the ' special pair'.The reduction factors vary strongly between 1.2 and 3.5, and only their average value is close to 2. The same behaviour is observed when comparing the nitrogen hyperfine coupling constants of 15N-labelled BChl a+ and P&0.40,41 As a result of the ENDOR/TRIPLE-in-solution experiments we make the following conclusions. (i) in Rps. sphaeroides and in R. rubrum reaction centres the primary donor cation P&o consists of a (BChl a): dimer supermolecule with the unpaired electron sitting in a super-molecular orbital delocalized over both dimer halves. Within the TRIPLE resolution this dimer exhibits C, symmetry in its spin density distribution. (ii) in Rps. uiridis reaction centres the primary donor PlG0 also consists of a dimer supermolecule, (BChl b); which, however, shows an asymmetric spin density distribution (on average 1 : 1.6) over the dimer halves.30 As a next step, extended molecular-orbital calculations are currently being performed, using the RHF-INDO/SP method, in order to determine the energy-minimized structures of the dimers with their s-spin density distributions, which can be compared with the ENDOR/TRIPLE results.From the ' vacuum ' calculations, i.e. without including possible perturbations by the surrounding proteins, the most stable dimer configuration for both (BChl a); 31 and (BChl b): 42 is obtained from a strong overlap of the systems in a face-to-face stacking with pyrrole rings I over each other and from the formation of two Mg-0 bonds between the acetyl groups of the monomeric components.Furthermore, the ' vacuum ' calculations predict approximate C, symmetry in the spin density distribution of (BChl a);, but not such a symmetry for (BChl b);. As can be seen from fig. 8, for (BChl a): as an example, this energy-minimized3480 Multiple Resonances involving E.S.R., N.M.R. and Optical Transitions Fig. 8. Comparison of experimental (dotted lines) and calculated (RHF-INDO/SP method, solid lines) s-spin densities for the dimer cation radical (BChl a): with pyrrole rings ‘I over I’ corresponding to the structure of lowest energy. The s-spin density values are proportional to the areas of the circles (p > 0) and squares (p, < 0), respectively. The vertical distance between the I rings is 3.1 A; for details, see ref.(31). structure has an s-spin density distribution which is in close agreement with the ENDOR/TRIPLE results. Moreover, the overall features of this structure are very similar to the X-ray structure of the Rps. viridis reaction centre ‘special pair’ for which, for instance, a ‘ I over I ’ dimer configuration was also determined.33 There are, however, characteristic differences emerging : whereas the ‘ vacuum ’ calculations show that Mg-0 bonds involving the acetyl groups contribute considerably to the energy stabilization of the dimer, in the X-ray structure, after refinement33 the oxygens of the acetyl groups are located away from the magnesium atoms. Obviously, the amino-acid environment of the dimer contributes significantly to the energy stabilization of the dimer, so that formation of Mg-0 bonds is no longer energetically favourable.From the available coordinates of the amino-acid residues it is obvious that the protein environment is not symmetrically organized with respect to the L and M branches of the chromophores. This asymmetry in the environment even holds for the L and M halves of the ‘special pair’. When the eight nearest amino-acid residues with their 76 atomic point charges are included in the RHF-INDO/SP molecular-orbital calc~lations~~ of the (BChl b); dimer (using the X-ray structure coordinates of the Rps. viridis reaction centre33) one obtains an enhanced asymmetry in the charge and spin density distributions over the L and M halves of the dimer supermolecule which, for the spin density distribution, is of similar magnitude as the observed averaged asymmetry ratio of 1 : 1.6.These results are now used in an attempt to understand the observed3’ branching ratio kET/kET z 6 of the electron-transfer rates via the L and M branches of the reaction centre.44 Finally, the result for the doublet-state radicals P&o and PlG0 concerning the symmetryK. Mobius 348 1 of the electronic distributions are supported by recent triplet-state experiments on illuminated reaction centres with a blocked electron-transfer chain : while the ENDOR results from polycrystalline reaction centres of Rps. sphaeroides show that P;f70 is a dimer with a symmetric electronic d i s t r i b ~ t i o n , ~ ~ the e.s.r. results from single-crystal reaction centres of Rps.viridis reveal that P&,, is a dimer with an asymmetric electronic distribution. 46-48 CIDEP-enhanced ENDOR on Transient Radicals in Solution Principles Since steady-state ENDOR/TRIPLE resonance in solution only reaches a sensitivity of ca. 10 O/O of e.s.r., realistic sensitivity estimates for successful ENDOR require a minimum of 1013 radicals in the cavity. As a consequence, the ENDOR investigation of short-lived radicals is restricted to lifetimes z 2 lop3 s, even when using fast-flow systems. Many important chemical reactions in photochemistry and radiolysis, however, in- volve transient radicals of unknown structure with lifetimes much shorter than s. When aiming at structure information via hyperfine couplings, which are typically in the order of some MHz, intermediates with lifetimes not shorter than lop6 s become particularly interesting.To obtain these intermediates accessible to ENDOR spectroscopy with its inherent resolution potential, advantage has to be taken of the large non-Boltzmann-type population differences created by dynamic polarization effects such as CIDNP (chemically induced dynamic nuclear polarization) or CIDEP (chemically induced dynamic electron polarization). The field of dynamic polarization is extensively covered in the l i t e r a t ~ r e , ~ ~ therefore only a brief summary will be given here. The large deviations from Boltzmann equilibrium populations (spectra in emission and/or in enhanced absorption are observed) are due to singlet-triplet (S-T) mixing in the intermediate species.Two established mechanisms are responsible for spin polarization effects in solution : (i) the triplet mechanism, where the polarization originates in selective singlet-triplet intersystem crossing in the excited molecule, which reacts chemically to produce polarized radicals, and (ii) the radical-pair mechanisms, where the polarization originates in radical encounters, diffusive separations and re-encounters. If the chemical reactions proceed in times shorter than the spin--lattice relaxation times of the radical intermediates, polarization can be transferred to more stable products. In CIDNP experiments the non-Boltzmann intensity distribution is observable in the n.m.r. spectrum of diamagnetic products, whereas in CIDEP experiments deviations from the Boltzmann distribution might show up in the e.s.r.spectrum of paramagnetic products. Mechanism (i) results in 'net effect' polarization, i.e. all lines in the spectrum are either in emission or in enhanced absorption. In mechanism (ii) in high magnetic fields, on the other hand, the S-To mixing coefficient, q2, which is the difference in electron spin precession frequencies of radicals 1 and 2 in their local magnetic fields, contains contributions from the Zeeman and hyperfine interactions : i Consequently, when the Ag contribution to o12 dominates, there will be no M, dependence, and a net polarization effect results, whereas for dominating hyperfine contribution the polarization pattern becomes dependent on M I , with some lines in emission and other lines in enhanced absorption (the 'multiplet effect').Often a superposition of net and multiplet effect polarizations is observed.3482 Multiple Resonances involving E.S.R., N.M. R. and Optical Transitions Spin energy and population diagram for an electron in a magnetic field interacting with an .ucleus and showing a net effect polarization (case 1) and a multiplet effect polarization (case 2). Saturated e.s.r. and n.m.r. transitions are indicated by open arrows. To explain the CIDEP-enhanced ENDOR detection strategy the simplest model case of a radical (S = i) containing one proton ( I = i) will be considered. We assume that spin-lattice relaxation can be ignored, i.e. signals are detected after photolytic generation in a time shorter than the spin-lattice relaxation time.For the detection strategy the net effect CIDEP has to be distinguished from the multiplet effect CIDEP. In fig. 9 case (1) represents a pure net effect polarization, whereas case (2) represents a pure multiplet effect polarization. It is easy to see that in case (1) a population difference between the nuclear spin levels has to be established first, for instance by a saturating microwave field. Driving the n.m.r. transition further transfers population from the pa level to the empty #ID levels, so that the population difference between the levels connected by the e.s.r. transition is increased, resulting in an enhanced e.s.r. signal (an enhanced emission signal in this case). For the second n.m.r. transition an enhancement is also obtained. In the case of a multiplet-effect polarization [fig.9, case (2)] there is already an initial population difference between the nuclear spin levels, and for the observed e.s.r. transition saturation must be avoided in order not to reduce this polarization. Driving the n.m.r. transition decreases the population difference between the levels connected by the e.s.r. transition, which results in a decreased e.s.r. signal. Net effect polarization can therefore easily be discriminated from multiplet effect polarization, since in the former case e.s.r. and ENDOR signals will have the same phase, whereas in the latter case they have opposite phases. The critical condition for this experiment is the r.f. field strength, B,, necessary to saturate n.m.r. transitions of transient radicals during their lifetime, z.The n.m.r. saturation condition for a transient radical is given by with T:,;1, = T;,,12, + z-' + 7;' (z, is the delay time between the photolysing laser pulse and the boxcar gate in the detection channel). For the p-benzosemiquinone radical (7 = 1 ms, q, z &, z z, = 4 p s ) the saturating r.f. field strength is estimated to be 20 G (rotating frame). To obtain this field strength with reasonable r.f. power is not an easy task; in our TM,,, cavity/coil configuration typically 1 kW is required.K. Mobius 3483 k 2 34 1 0 ' emission I 5 VH I I I I I I I I I I I I ~ I I I ' 10 15 20 frequency/M Hz Fig. 10. Time-resolved e.s.r. (a) and ENDOR (b) spectra of p-benzosemiquinone radicals in ethylene glycol solution detected 5 p s after creation by 10 ns U.V.pulses at 308 nm of a XeCl excimer laser with a repetition rate of 50 Hz. The solution was kept flowing at T = 303 K. For ENDOR the e.s.r. line indicated by an arrow was chosen for detection applying saturating microwave and r.f. fields. For experimental details, see ref. (51). The measured hyperfine constants are a, = - 14.00k0.02 MHz; a2 = -5.13kO.02 MHz; a, = 0.53+0.02 MHz. Examples : Net Effect us. Multiplet Effect Polarization The first CIDEP-enhanced ENDOR experiment was performed in a C.W. mode of dete~tion.~' A drastically improved signal-to-noise ratio is obtained by time-resolved detection ca. 1 ps after the laser pulse has started the photoreaction, since in this mode a large fraction of the initial polarization can be m~nitored.~' As a test system for net effect polarization, u.v.-irradiated p-benzoquinone in ethylene glycol solution was chosen, because earlier e.s.r.studies have that the observed CIDEP is due to a dominant triplet mechanism with only very weak radical pair mechanism contributions. The photoreaction proceeds via singlet excited benzoquinone, intersystem crossing to triplet excited benzoquinone and abstraction of a hydrogen atom from the solvent under formation of the polarized p-benzosemiquinone radical (PBQH'). Fig. 10 depicts the e.s.r. and ENDOR spectra of PBQH' detected in the time-resolved3484 Multiple Resonances incolving E.S.R., N.M. R. and Optical Transitions absorption emission ( b l CH; L h a4/2 1 '( I I 1 i I ' " If v " emission vH Fig.11. Time-resolved e.s.r. (a) and ENDOR (b) spectra of benzyl radicals in propanediol solution detected 4 ps after creation by 10 ns U.V. pulses at 308 nm of a XeCl excimer laser with a repetition rate of 50 Hz. The solution was kept flowing at T = 298 K. For ENDOR the e.s.r. line indicated by an arrow was chosen for detection applying a non-saturating microwave and a saturating r.f. field. For experimental details see ref. (51). The measured hyperfine constants are a, = 4.95 k0.05 MHz, a, = - 14.39k0.02 MHz, a, = - 17.35 k0.05 MHz and a4 = -45.7k0.1 MHz. mode. All the e.s.r. lines appear in emission, as do the ENDOR lines; this reflects an increase of the e.s.r. amplitudes. This demonstrates that the net effect dominates the polarization mechanism. The ENDOR intensity amounts to ca.10% of the e.s.r. intensity and could be increased by a factor of 2 when, in a Special TRIPLE experiment, the two n.m.r. transitions belonging to one particular hyperfine coupling were driven simultaneously. Furthermore, relative signs of the hyperfine couplings could be determined from the General TRIPLE version of the experiment. As a test system for the multiplet effect polarization, u.v.-irradiated dibenzylketone in propanediol was ~elected.~' Earlier e.s.r. experiment^^^-^^ have revealed that in this photoreaction benzyl radicals with almost pure multiplet CIDEP are produced. In the radical-pair-mechanism polarization scheme two identical benzyl radicals form the radical pair. They are produced via photoinduced bond cleavage and decarbonylation reactions.Consequently, in eqn (4) the Ag term vanishes and the population differenceK. Mobius 3485 of the two energy levels connected by an n.m.r. transition, and thereby the ENDOR effect, becomes proportional to the hyperfine coupling aj. Large ENDOR effects are therefore expected for lines corresponding to large ui, whereas lines corresponding to small aj should be weaker. Fig. 11 shows the strong multiplet effect polarization in the time-resolved mode of detection after pulsed laser excitation : the low-field half of the e.s.r. spectrum is in emission, the high-field half in enhanced absorption. Depending on the magnetic spin quantum number MI; of the e.s.r. line and its polarity being selected for the ENDOR experiment, the ENDOR effect shows up either in a decreased absorption or a decreased emission in accordance with a dominating multiplet effect.Almost 100% changes in the e.s.r. intensity could be observed for the largest hyperfine coupling. From these first results it is concluded that CIDEP-enhanced ENDOR and TRIPLE of transients have promising future potential for the characterization of those photochemically generated radicals and photoexcited triplet states which show pronounced CIDEP effects in their e.s.r. spectra. On-going CIDEP-enhanced ENDOR experiments comprise u.v.-induced transient radicals of complex photopolymerization initiators like, for instance, co,co-dimethoxy-co-phenylacetophenone57 and light-induced triplet states of primary donors in photosynthesis, e.g. reaction-centre preparations of the purple bacteria Rps.sphaeroides. '' Zero-field ODMR and ODNQR on Photoexcited Triplet State Molecules in Frozen Glasses Principles In certain situations it might be advantageous to use triplet-state electrons rather than the unpaired electron of a doublet state for probing spatial and electronic structures. For the frequently occurring case of polycrystalline samples of excited-state molecules, zero- field ODMR and variants thereof are the methods of choice, since they combine high spectral resolution with high sensitivity. High resolution is achieved since, in zero magnetic field, there is no line broadening due to anisotropic Zeeman and dipolar hyperfine interactions. Whereas quadrupolar hyperfine structure remains as a first-order effect, dipolar hyperfine structure vanishes to first order.Using fig. 12 the basic strategy of the ODMR experiment can be explained briefly. For an organic molecule such as the aza-aromatics a ~ r i d i n e , ~ ~ p h e n a ~ i n e ~ ~ and pyrazine,60 the lowest excited state is a triplet state, T,, which is split into three electron spin sublevels, T,, Ty and T,, by the electron dipoledipole interaction. In zero field the subscripts refer to the molecular axes system x, y and z. Each sublevel may also contain small admixtures of various low-lying singlet states, Si, as a result of spin-orbit coupling. Provided the symmetry of the molecule is sufficiently high, dominant admixture of the first excited singlet state, S,, to just one spin sublevel of T, will occur, e.g. to T, in acridine.An important consequence of this symmetry-controlled singlet-triplet mixing is the selectivity of the intersystem crossing and the radiative/non-radiative decay processes. Optical pumping into the S, electronic state, followed by a spin-selective intersystem crossing thus allows the preparation of T, with a high degree of spin polarization. At temperatures low enough to make the spin-lattice relaxation between the sublevels slow compared with the decay processes, this polarization will exist for the lifetime of the triplet state. Since the radiative/non-radiative populating and depopulating processes depend on the electronic part of the wavefunction only, all the levels within a nuclear spin manifold u, u etc. originating from the same electron spin sublevel will have identical photokinetic characteristics.Detection of microwave transitions in phosphorescent triplet excited states may therefore be performed optically3486 Multiple Resonances involving E.S.R., N.M.R. and Optical Transitions / \ k, ( I sc 1 I Fig. 12. Spin energies and populating/depopulating processes in the lowest triplet excited state, T,, of a typical aza-aromatic molecule (acridine) in a zero-field ODMR experiment. After S,++S, excitation, a resonant microwave field is applied to induce intensity changes of the phosphorescence. The energy scale is magnified by ca. lo5 in order to indicate the fine and hyperfine structures of TI. For details, see text. by monitoring the change in phosphorescence intensity, AIphos, brought about by resonant transfers of population from one electron spin sublevel to another : where eqn ( 5 ) is valid for saturating microwave irradiation.(ki are radiative decay rates and Ni are initial population numbers.) In an optically detected electron-nuclear double-resonance experiment, in addition to the microwave transition, e.g. the X - Y = 2E transition in fig. 12, transitions within the nuclear manifold of an electron spin sublevel are driven by saturating r.f. fields. Phosphorescence intensity changes created by applying both microwave and r.f. fields to the spin system establish variants of the ODMR experiments appropriately called ODENDOR61,62 and ODNQR.63-65 As we see, the logical application of zero-field electron-nuclear double resonance techniques lies in the determination of nuclear quadrupole interaction tensors, because quadrupolar hyperfine structure appears in first order, dipolar hyperfine structure onlyK.Mobius 3487 0 time + Fig. 13. Pulse strategy for the ODNQR experiment with its various stages (aHd) with increasing times after the laser pulse. The upper part depicts the population development, the middle part the development of the phosphorescence intensity, and the lower part the timing of the microwave pulses at vl, v 2 and of the r.f. pulse at v3. For details, see text. in second order. There is, however, a fundamental problem in this reasoning : despite its second-order character, the dipolar hyperfine interaction dictates with its largest component which element of the nuclear quadrupole tensor will be accessible to an ODENDOR experiment.The reason lies in the familiar hyperfine enhancemenP of nuclear transition probabilities, by which all the weaker second-order transitions are masked beyond detectability. As a consequence, only one difference of nuclear quadrupole principal values (the one dictated by the largest dipolar hyperfine component) can be revealed by zero-field ODMR or ODENDOR, and not the complete quadrupole tensor.63* 64 To obviate this fundamental difficulty, one must devise a strategy to remove selectively the dominating hyperfine-enhanced n.q.r. transitions from the spectrum. Thus one must create a situation where the levels involved in such transitions are empty. One must rather populate those substates of the spin system where minimal hyperfine admixture is present.When driving n.q.r. transitions between these uncontaminated sub- states, no hyperfine enhancement can occur, and high-resolution n.q.r. spectra are prin- cipally obtainable. This is the underlying principle of the pulsed ODNQR strategy.63 To exploit the high-resolution capability of the ODNQR technique for polycrystalline samples, it is mandatory to minimize the ODMR linewidth. This can be achieved in the following ways : (i) optical site-selection techniques such as narrow-band laser excitation should be applied59 to excite only guest molecules having very similar electronic and structural environments, (ii) the polycrystalline hosts should exhibit the properties of Shpolskii in which well resolved optical spectra of appropriate guest molecules can be obtained, (iii) the guest molecules, and, preferably, also the host molecules should be fully deuterated to minimize line-broadening from unresolved second-order hyperfine interactions.is illustrated in fig. 13. After the 10 ns laser pulse [excitation stage (a)] the T, manifold is populated via electron spin- selective intersystem crossing (T, is empty and non-radiating). Immediately following this, a microwave ‘store’ pulse is applied [stage (b)] at a resonance frequency v, and a The pulse strategy of the ODNQR3488 Multiple Resonances involving E.S.R., N.M. R. and Optical Transitions 0 2a 4a 8a ' allowed ' - b I r-t 'forbidden' I I I 1 I I I I 1 I I b 660 6 70 680 v,,/MHz Fig. 14.2E ODMR spectrum of [2H,]phenazine in biphenyl at T = 1.2 K.For experimental details see ref. (59); for definition of the spectral parameters see text. power level sufficient for saturating a T,t+T, transition. Owing to the long lifetime of T,, ample time is gained to establish r.f.-induced resonant population transfer at v3 between two nuclear spin levels within the nuclear manifold u, t i etc. [stage (c)]. Since T, is non-radiating, a microwave 'recall' pulse has to be applied [stage (d)] at a resonance frequency v, to produce a phosphorescence signal which is monitored in the photon- counting gate B. All three resonance conditions for vl, v, and v3 must be fulfilled before a phosphorescence signal may be observed in gate B. Thereby the ODNQR experiment is distinguished by a high degree of selectivity.Futhermore, high spectral sensitivity is also achieved because, other than in conventional ODMR, the signal is compared with the dark counts monitored in gate A. Examples : Nitrogen Heterocycles As first examples for high-resolution ODMR and ODNQR experiments we have chosen the aza-aromatic molecules acridine," phenazine" and pyrazine,60 with the primary goal of determining the 14N and ,D nuclear quadrupole tensors. These molecules are particularly suited for these experiments because their intersystem crossing and radiative decay processes are highly selective, so that, to a good approximation, only one electronic substate is populated, and only this state decays radiatively . Fig. 14 shows the high-resolution ODMR spectrum of [2H,]phenazine obtained by narrow-band laser excitation when the microwave frequency is swept around the Xt* Y = 2E transition region.The analysis of this spectrum5' requires a spin Hamiltonian incorporating the electron spin-spin interaction and the nuclear quadrupole and dipolar hyperfine interactions of the two 14N nuclei: Z = Zss + Znq + Z h f with Z S J h = X$ - YSE - Zs,Z 3EpnqIh = - E , ~ - E , ~ - - E , ~ Z ~ Z h f / h = A,, S, f, + A,, SY i, +A,, 3, f,.K. Mobius 3489 I I I I I - 655 660 665 670 675 v,,IMHz 0 100 +r/ms I I I I I 1 I t 0 1 2 3 4 5 V,c /MHz Fig. 15. (a) 2EODMR and (b) ODNQR spectra of [2H,]phenazine in [2H1,]-n-heptane at T = I .2 K. For details see ref. (63) and (64); for definition of the spectral parameters see text. The main features of the spectrum are explained by considering only the out-of-plane component A,, of Xhf of the two equivalent 14N nuclei, which dominates the in-plane components by about an order of magnitude.in accordance with experiment, that the 2E spectrum consists of four 'allowed' lines, where only the electronic spin part of the wavefunction is changed, and two ' forbidden ' satellites, where the electronic and 14N spin states are changed simultaneously. The ' allowed ' transitions occur at v,, v, + 2a, v, + 4a and v, + 8a, where vo is the pure 2E transition frequency and a = [A,,(N)I2/2E. The 'forbidden' lines show up at sufficiently high microwave power levels at the frequencies v, +4a & b with b = { 4 ( ~ , - & J 2 + 16a2}i i.e. they contain information about one difference of principal values of the 14N nuclear quadruple tensor: A,,(N) = 28.8 MHz; IE,-EJ = 3.0 MHz.Since only one difference of E values is accessible, the complete 14N nuclear quadrupole tensor cannot be determined by ODMR or even by C.W. ODENDOR. However, the pulsed ODNQR experiment gives access to this information. By means Second-order perturbation theory3490 Multiple Resonances involving E.S.R., N.M.R. and Optical Transitions of the described three-pulse sequence the weak transitions required for the full nuclear quadrupole tensor information are no longer masked by the strong A,,(N) hyperfine enhanced transition. In fig. 15 ODMR and ODNQR spectra of [2H,]phenazine are depicted. The ‘store’ pulse is applied at the frequency vo within the 2E spectrum, the ‘recall ’ pulse at the frequency vo + 2a.For this situation a four-line ODNQR spectrum is observed with transition frequencies - E,) & al. Since the values of a and IE,-E,I can be extracted from the 2E ODMR spectrum, the full 14N-nuclear quadrupole tensor can be d e t e m ~ i n e d . ~ ~ , ~ ~ Assuming that the 14N lone-pair direction (y axis) defines the main axis of the nuclear quadrupole tensor ( E ~ positive and largest in magnitude) the triplet-state nuclear-quadrupole parameters for phenazine are e2qQ/h = -4.36 MHz and q = 0.21. When comparing these values with the singlet ground-state data6, (e2qQ/h = -4.32 MHz, q = 0.37) we see that only the asymmetry parameter q changes drastically upon electronic excitation. Advanced molecular orbital calculations are needed to rationalize this obser~ation.~~ In ongoing ODMR and ODNQR experiments it is attempted to extend the field of application to biologically interesting systems such as porphyrins. First results have been obtained for zinc octaethylporphyrin in its ground and excited ~tates.~’ In concluding, I return to the title of my lecture, multiple resonances - more than just a game? There is no doubt that our multiple resonance experiments show typical features of a game : the on-going oscillations between fun and frustration.But beyond that, the results obtained so far encourage us to continue in playing for high stakes on the determination of electronic and spatial structures of complex molecules. We put our faith in the feasibility of finding relations between form and function of these molecules, relations which govern the role of these molecules in important photochemical reactions.- E,) f a1 and Outstanding contributions to the development of our multiple resonance methods on singlet-, doublet- and triplet-state molecules came from the following former and present collaborators : E. Bergmann, R. Biehl, C. v. Borczyskowski, E. Boroske, 0. Burghaus, K. P. Dinse, W. Frohling, E. Haindl, V. Hamacher, P. Jaegermann, F. Lendzian, W. Lubitz, L. Mayas, W. Mohl, M. Plato, 0. Takizawa and C . J. Winscom, to all of whom I express my gratitude. My present collaborators in the investigations of primary products in photosynthesis are Friedhelm Lendzian, Wolfgang Lubitz and Martina Huber concerning experiments, and Martin Plato and Eberhard Trankle with regard to theory. Biological expertise and biochemical preparations were contributed by Hugo Scheer (Munich) and Arnold Hoff (Leiden).My present collaborators in the CIDEP-ENDOR experiments on transient radicals are Friedhelm Lendzian, Petra Jaegermann and Renad Sagdeev (Novosibirsk). The work on zero-field ODMR and ODNQR on nitrogen heterocycles was largely carried out by Chris Winscom, Werner Frohling and Peter Dinse. To all these co-workers I am particularly indebted, and with them I share the honour of this Bruker Lecture award. The long-standing cooperation with Harry Kurreck from the Institute of Organic Chemistry is acknowledged with gratitude, as is the generous support of our work by the Deutsche Forschungsgemeinschaft (Sfb 161, Sfb 337). References 1 G.Feher, Phys. Rev., 1956, 103, 834. 2 J. S. Hyde and A. H. Maki, J . Chem. Phys., 1964, 40, 31 17. 3 J. H. Freed, in Multiple Electron Resonance Spectroscopy, ed. M. M. Dorio and J. H. Freed (Plenum 4 J. Schmidt and J. H. van der Waals, Chem. Phys. Lett., 1968, 2, 640. Press, New York, 1979), p. 73.K. Mobius 349 1 5 A. J. Hoff and K. Mobius, Proc. Natl Acad. Sci. USA, 1978, 75, 2296. 6 W. Lubitz, F. Lendzian, H. Scheer, M. Plato and K . Mobius, unpublished work. 7 F. Lendzian, K. Mobius, M. Plato, U. H. Smith, M. C. Thurnauer and W. Lubitz, Chem. Phys. Lett., 8 K. Mobius, M. Plato and W. Lubitz, Phys. Rep., 1982, 87, 171. 9 K. P. Dinse, R. Biehl and K. Mobius, J . Chem. Phys., 1974, 61, 4335. 1984, 111, 583. 10 K. Mobius and R. Biehl, in Multiple Electron Resonance Spectroscopy, ed.M. M. Dorio and J. H. 11 R. Biehl, M. Plato and K. Mobius, J. Chem. Phys., 1975, 63, 3515. 12 J. H. Freed, J. Chem. Phys., 1965, 43, 2312. 13 J. H. Freed, J . Phys. Chem., 1967, 71, 38. 14 J. H. Freed, D. S. Leniart and J. S . Hyde, J . Chem. Phys., 1967, 47, 2762. 15 J. H. Freed, D. S. Leniart and H. D. Connor, J . Chem. Phys., 1973, 58, 3089. 16 J. H. Freed, in Electron Spin Relaxation in Liquids, ed. L. T. Muus and P. W. Atkins (Plenum Press, 17 A. G. Redfield, Adv. Magn. Reson., 1965, 1, 1. 18 M. Plato, W. Lubitz and K. Mobius, J . Phys. Chem., 1981, 85, 1202. 19 W. Mohl, C. J. Winscom, M. Plato, K. Mobius and W. Lubitz, J . Phys. Chem., 1982, 86, 149. 20 K. P. Dinse, K. Mobius and R. Biehl, 2. Naturforsch., Teil A, 1973, 28, 1069.21 F. Bloch, Phys. Rev., 1956, 102, 104. 22 W. Lubitz, F. Lendzian and K. Mobius, Chem. Phys. Lett., 1981, 81, 235. 23 F. Lendzian, W. Lubitz, H. Scheer, C. Bubenzer and K. Mobius, J . Am. Chem. Soc., 1981, 103, 4635. 24 W. Lubitz, F. Lendzian and K. Mobius, Chem. Phys. Lett., 1981, 84, 33. 25 A. J. Hoff, F. Lendzian, K. Mobius and W. Lubitz, Chem. Phys. Lett., 1982, 85, 3. 26 F. Lendzian, K. Mobius and W. Lubitz, Chem. Phys. Lett., 1982, 90, 375. 27 W. Lubitz, F. Lendzian, H. Scheer, J. Gottstein, M. Plato and K. Mobius, Proc. Nut1 Acad. Sci. USA, 1984, 81, 1401. 28 F. Lendzian, W. Lubitz, R. Steiner, E. Trankle, M. Plato, H. Scheer and K. Mobius, Chem. Phys. Lett., 1986, 126, 290. 29 M. Huber, F. Lendzian, W. Lubitz, E. Trankle, K. Mobius and M. R. Wasielewski, Chem.Phys. Lett., 1986, 132, 467. 30 W. Lubitz, F. Lendzian, M. Plato, E. Trinkle and K. Mobius, Proc. X X I I I Congress Ampere on Magnetic Resonance, ed. B. Maraviglia, F. De Luca and R. Campanella (Instituto Superiore di Sanita, Rome, 1986), p. 486. 31 M. Plato, E. Trankle, W. Lubitz, F. Lendzian and K. Mobius, Chem. Phys., 1986, 107, 185. 32 J. R. Norris, R. A. Uphaus, H. L. Crespi and J. J. Katz, Proc. Nut1 Acad. Sci. USA, 1971, 68, 625. 33 H. Michel, 0. Epp and J. Deisenhofer, Eur. Mol. Biol. Organ. J., 1986, 5, 2445. 34 C. A. Wraight and R. K. Clayton, Biochim. Biophys. Acta, 1974, 333, 246. 35 C. A. Wraight, J. S. Leigh, P. L. Dutton and R. K. Clayton, Biochim. Biophys. Acta, 1974, 333. 401. 36 G. Feher and M. Y. Okamura, in The Photosynthetic Bacteria, ed.R. K. Clayton and W. R. Sistrom 37 J. K. H. Horber, W. Gobel, A. Ogrodnik, M. E. Michel-Beyerle and R. J. Cogdell, FEBS Lett., 1986, 38 G. Feher, A. J. Hoff, R. A. Isaacson and L. C. Ackerson, Ann. N. Y. Acad. Sci., 1975, 244, 239. 39 J. R. Norris, H. Scheer and J. J. Katz, Ann. N.Y. Acad. Sci., 1975, 244, 260. 40 W. Lubitz, R. A. Isaacson, E. C. Abresch and G . Feher, Proc. Natl Acad. Sci. USA, 1984, 81, 7792. 41 W. Lubitz, F. Lendzian, M. Plato, K. Mobius and E. Trankle, in Antennas and Reaction Centers of Photosynthetic Bacteria, ed. M. E. Michel-Beyerle (Springer-Verlag, Berlin, 1985), p. 164. 42 E. Trankle and M. Plato, 1986, unpublished results. 43 M. Plato, 1987, unpublished results. 44 M. E. Michel-Beyerle, M. Plato, J. Deisenhofer, H. Michel, J.Jortner and M. Bixon, Biochim. Biophys. 45 F. Lendzian, H. van Willigen, S. Sastry, H. Scheer and R. Feick, Chem. Phys. Lett., 1985, 118, 145. 46 P. Gast, M. R. Wasielewski, M. Schiffer and J. R. Norris, Nature (London), 1983, 305, 451. 47 P. Gast and J. R. Norris, FEBS Lett., 1984, 177, 277. 48 J. R. Norris, D. E. Budil, H. L. Crespi, M. K. Bowman, P. Gast, C. P. Lin, C. H. Chang and M. Schiffer, in Antennas and Reaction Centers of Photosynthetic Bacteria, ed. M. E. Michel-Beyerle (Springer-Verlag, Berlin, 1985), p. 147. 49 See, for instance (a) L. T. Muus, P. W. Atkins, K. A. McLauchlan and J. B. Pedersen, Chemically Induced Magnetic Polarization (Reidel, Dordrecht, 1977); (b) F. J. Adrian in (a), pp. 77 and 369; (c) P. W. Atkins and G. T. Evans, Adv. Chem. Phys., 1976,35, I ; ( d ) J. H. Freed and J. B. Pedersen, Adv. Magn. Reson., 1976, 8, 1 ; (e) P. J. Hore, C. G . J o s h and K. A. McLauchlan, in Electron Spin Resonance, ed. P. B. Ayscough (Specialist Periodical Report, The Chemical Society, London, 1979), vol. 5, p. 1 ; (f> A. D. Trifunac and M. C. Thurnauer, in Time-Resolved Electron Spin Resonance of Freed (Plenum Press, New York, 1979), p. 475. New York, 1972), p. 503. (Plenum Press, New York, 1978), p, 349. 198, 268. Acta, 1987, submitted for publication.3492 Multiple Resonances involving E.S. R., N.M. R. and Optical Transitions Transient Radicals in Liquids, ed. L. Kevan and R. N. Schwartz (John Wiley, New York, 1979), p. 107; ( g ) M. C. Depew and J. K. S. Wan, Magn. Reson. Rev., 1983, 8, 85; (h) A. J. Hoff, Q. Rev. Biophys., 1984, 17, 153; (z9 K. M. Salikhov, Yu. N. Molin, R. Z. Sagdeev and A. L. Buchachenko, Spin Polarization and Magnetic Eflects in Radical Reactions (Elsevier, Amsterdam, 1984). 50 R. Z. Sagdeev, W. Mohl and K. Mobius, J . Phys. Chem., 1983, 87, 3183. 51 F. Lendzian, P. Jaegermann and K. Mobius, Chem. Phys. Lett., 1985, 120, 195. 52 L. T. Muus, S . Frydjaer and K. B. Nielsen, Chem. Phys., 1978, 30, 163. 53 H. Paul and H. Fischer, Helv. Chim. Acta, 1973, 56, 1575. 54 H. Langhals and H. Fischer, Chem. Ber., 1978, 111, 543. 55 A. I. Grant and K. A. McLauchlan, Chem. Phys. Lett., 1983, 101, 120. 56 R. Baer and H. Paul, Chem. Phys., 1984, 87, 73. 57 P. Jaegermann, F. Lendzian, G. Rist and K. Mobius, unpublished work. 58 W. Frohling, C. J. Winscom and K. Mobius, Chem. Phys., 1981, 60, 301. 59 W. Frohling, C. J. Winscom. K. P. Dinse and K. Mobius, Chem. Phys., 1980, 51, 369. 60 W. Frohling, C. J. Winscom and K. Mobius, Chem. Phys., 1983, 75, 389. 61 C. B. Harris, D. S. Tinti, M. A. El-Sayed and A. H. Maki, Chem. Phys. Lett., 1969, 4, 409. 62 I. Y. Chan, J. Schmidt and J. H. van der Waals, Chem. Phys. Lett., 1969, 4, 269. 63 K. P. Dinse and C. J. Winscom, J . Chem. Phys., 1978, 68, 1337. 64 K. P. Dinse and C. J. Winscom, in Triplet State ODMR Spectroscopy, ed. R. H. Clarke (John Wiley, 65 K. Mobius, W. Frohling, F. Lendzian, W. Lubitz, M. Plato and C. J. Winscom, J . Phys. Chem., 1982, 66 S. Geschwind, in HyperJine Interactions, ed. A. J. Freeman and R. B. Frankel (Academic Press, New 67 E. V. Shpolskii and L. A. Klimova, Opt. Spectrosc., 1959, 7, 499. 68 L. Guibe and E. A. C. Lucken, Mol. Phys., 1966, 10, 273. 69 C. J. Winscom, A. L. Maniero and K. Mobius, Chem. Phys. Lett., 1986, 128, 244. 70 J. Deisenhofer, R. Huber and H. Michel, Nachr. Chem. Tech. Lab., 1986, 34, 416. 71 J. R. Norris, C. P. Lin and D. E. Budil, J . Chem. SOC., Furuday Trans. I , 1987, 83, 13. New York, 1982), p. 83. 86,4491. York, 1967), p. 225. Paper 7/901; Received 19th May, 1987

ISSN:0300-9599    

DOI:10.1039/F19878303469

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. SOC., Faraday Trans. I , 1987, 83 (12), 3493-3503 MAGRES: A General Program for Electron Spin Resonance, ENDOR and ESEEM Cornelus P. Keijzers," Ed J. Reijerse, Pieter Stam, Michiel F. Dumont and Michiel C. M. Gribnau Department of Molecular Spectroscopy, Research Institute of Materials, University of Nijmegen, Toernooiveld, 6525 ED Nijmegen, The Netherlands The program package MAGRES (MAcnetic msonance) is able to calculate e.s.r., ENDOR (without relaxation) and ESEEM spectra for, in principle, any spin system in single crystals as well as in powders. The spin Hamiltonian may be constructed from electron and/or nuclear Zeeman interactions, exchange and hyperfine couplings, zero-field splittings and nuclear quadrupole interactions. For the calculation of eigenvalues and eigenvectors the program uses exact diagonalization, hence no assumptions have to be made about the relative magnitude of the various interactions. Comparison of the calculated with the experimental frequencies of single- crystal spectra permits the optimization of the interaction tensors.The computed tensors may be checked by comparison of the experimental and the calculated intensities of single-crystal and powder spectra. Simulation of ESEEM spectra is possible for the two- and three-pulse sequence, and the effect of the dead-time may be included. The program can also be used for the calculation of C.W. n.m.r. spectra. The systems which are studied by e.s.r. and e.s.r.-related techniques (c.w.-ENDOR, ESEEM, ESE-ENDOR) are very diverse, and include model systems for biochemical molecules, crystals which show phase transitions, Jahn-Teller systems, metal dimers and clusters.' The nature of the electronic and nuclear spins involved and the relative magnitudes of the various spin-spin and spin-field interactions depend upon the particular system.Because in our laboratory all the above mentioned techniques are applied to the study of a wide variety of solid-state problems (transition-metal complexes with d o ~ b l e t ~ - ~ and t~-iplet~-~ ground states, Jahn-Teller systems,a-'o metal clusters,11 incommensurate systems12 and low-dimensional magnetic corn pound^^^-^^) the need for a general-purpose computer program has been felt for some time. This has resulted in the development of the program package MAGRES (Mmnetic REsonance). Originally the program was set up for the treatment of single-crystal e.s.r. spectra for a general spin ~ y s t e m .~ . ~ Now it is able to handle both single-crystal and powder spectra for general spin systems for all the abovementioned techniques (with some restrictions which will be mentioned below). The program package can also be used to calculate C.W. n.m.r. spectra. In this paper we describe the design of the program package, its input requirements and its various options. The versatility is illustrated with examples. Although the input is complex, a fact which is inherent in the experimental techniques, much attention has been paid to keeping the input as simple and user-friendly as possible. This is shown in fig. 1 by an input example for the calculation of a 14N-ESEEM spectrum for a powdered sample of nickel(r1) bis(dithi0carbamate) doped with copper(r1).34933494 A General Program for E.S.R., ENDOR and ESEEM * * Ni : Cu DTC ESEEM simulation with the program MAGRES * TENSOR IS0 xx YY TENSOR IS0 TENSOR IS0 xx YY TENSOR IS0 TENSOR xx YY * G tensor electron 2.041 - 0.023 - 0.020 * nuclear g value copper * hyperfine tensor copper 1.48040 - 84.5 42.6 41.4 0.40347 0.25 0.25 * nuclear g value nitrogen * nuclear quadrupole tensor nitrogen xz - 0.065 TENSOR * hyperfine tensor nitrogen xx 0.06 YY 0.06 ELECTRON electron 1 /2 1 NUCLEUS copper 3/2 2 HYPERFINE copper electron 3 * hyperfine; tensor 3 NUCLEUS nitrogen 1 4 5 * nitrogen I = 1; tensors 4, 5 HYPERFINE nitrogen electron 6 * hyperfine; tensor 6 THRESHOLD 1 .Om7 TEMPERATURE 15.0 ESEEM GAUSSIAN * pulse profile WIDTH 100.0 * pulse width TAU 0.200 * time between pulses 1 and 2 (3-pulse DEADTIME 0.800 TIME SAVE MAGNITUDE SAVE POWDER 30 * 2250 integration points in powder calculation SHAPE GAUSSIAN DERIVATIVE CHANNELS 0.01953125 WRITE * plotting info OUTPUT LAST PLOTTING SWEEP FREQUENCY SPECTRUM 3123.0 2.5 2.5 8409.0 IS0 -0.38 xz -0.015 * electron S = 1/2; tensor 1 * copper I = 3/2; tensor 2 * sequence) * save time-domain spectrum on file * save magnitude spectrum on file 0.075* lineshape and linewidth * specification of output options : plotting * frequency swept ESEEM spectrum from 0 to * 5MHz * magnetic field : 3 123.0 G * excitation frequency : 8409.0 MHz START ~~ Fig.1. Input dataset for the calculation of the spectrum of fig.5: a 14N ESEEM spectrum for a powdered sample of nickel(I1) bis(dithi0carbamate) doped with Cu". A line starting with * or text on a line following * is handled as comment by the program.C. P. Keijzers et al. 3495 Program Characteristics The Spin Hamiltonian All applications start with the calculation of the eigenvalues and eigenvectors of the spin Hamiltonian after the necessary input operations. The calculation of resonance frequencies/fields and intensities depends upon the specific technique which is applied, and this will be discussed in the appropriate sections. In the input routines of the program the spins, interactions and interaction tensors are defined. Spins may be defined as electron or nuclear, the difference being that the g tensors must be specified in Bohr magnetons or in nuclear magnetons.All half-integer and integer spins are allowed. In the following the term ‘electron spin’ will be used for any electronic spin state S 2 f. MAGRES recognizes six types of interactions: two field- dependent couplings (the electron and nuclear Zeeman interaction) and four field- independent couplings (the exchange interaction between two electron spins or two nuclear spins, the hyperfine interaction between an electron spin and a nuclear spin, the zero-field splitting of an electron spin S > + and the nuclear quadrupole interaction of a nuclear spin I > i). All and any number of combinations of spins and interactions are allowed. Every interaction is described by a second-rank tensor which may consist of an isotropic, a traceless symmetric and/or an antisymmetric part, which contain 1, 5 and 3 elements, respectively.(In case of zero field and quadrupole splitting the isotropic and antisymmetric parts are not allowed. The program will issue a warning in case of error.) The tensors may be defined by their elements in the laboratory frame of axes. A symmetric tensor may also be defined by its three principal values and the three Euler angles which specify the principal axes relative to the laboratory system. It is also posiible to define a tensor by its three principal values and the principal axes of another tensor, which is an easy way to force coinciding principal axes. The remainder of the required input will be discussed in the relevant sections.Eigenvalues and Eigenfunctions The basis functions for the calculations are the direct products of the S, and I, eigenfunctions of all the spins. The Hamilton matrix H is set up in the laboratory frame using spin matrices S,, S, and S, and I,, Iy and I, and direct product techniques. To save computing time when calculating a series of spectra with different magnetic field orientations, the field-independent part H, and the field-dependent part HBo- (for a field strength unity) of the Hamilton-matrix are calculated and stored separately. For each magnetic field direction the field-dependent Hamilton matrix is calculated and combined with the field-independent matrix. The resulting Hamilton matrix H = Ho+B,H,o=l is diagonalized : yielding the diagonal eigenvalue matrix E and the eigenfunction matrix C.E = C+HC Transition Probabilities If transition probabilities are needed the matrix HB1 of the perturbation Hamiltonian, which includes the anisotropy in the Zeeman interaction of all electron and nuclear spins, is set up on the same basis functions as used for HBo, and thereafter it is transformed into the H representation : CtHBIC = M (3)3496 A General Program for E.S.R., ENDOR and ESEEM yielding the transition moment matrix M. This two-index transformation is optimized for a sparse HB1 matrix by avoiding multiplication with zero elements of HB1 and by selecting the transitions in the spectral range of interest. The obtained set of transition positions and intensities can be plotted with a Gaussian or a Lorentzian lineshape, either in absorption or in derivative mode.Simulation vs. Optimization For single-crystal studies MAGRES may be used in two modes : spectrum simulation and tensor optimization. The simulation mode is well suited for a systematic study of the influence of the various experimental parameters. It may also be used to check the line intensities in a spectrum after the determination of the interaction tensors via the optimization mode. The two modes may also be used in one program run with the advantage that, for instance, before and/or after tensor optimization (selected) spectra may be simulated. In the simulation mode one of the two quantities field or frequency should be designated as ‘swept’; the other is automatically set to ‘fixed’. For ENDOR and ESEEM only frequency sweep is allowed, in accordance with the experimental set-up.A wide variety of output options is available to the user to show the results of the calculation. These options comprise printing of the Hamiltonian matrices, eigenvalues, eigenvectors, transition fields or frequencies and the interaction tensors and their relative orientations, as well as the plotting of a spectrum. For plotting the spectra the calculated resonance lines are collected in an array of channels for which the width in field or frequency units (whichever is swept) must be defined. In the optimization mode MAGRES is linked as a subroutine to the minimization program MI NU IT.^^ This allows for the optimization of the interaction tensors by comparison of the experimental with the calculated transition frequencies (without calculating the transition probabilities).To this end the user can declare any number of tensor elements (or the principal values and tensor orientations) as ‘variable’ ; the remaining ones are fixed. Starting from estimated values for the variable elements, MINUIT minimizes an error function which is calculated by MAGRES according to where vFPtl and v;lcd are the experimental and calculated transition frequencies, respectively. The summation runs over all assigned lines in all spectra. The error function is always calculated in the frequency domain: this means that in case of C.W. e.s.r. for every direction of B, a new H, = 1 is constructed. For every line position for a certain direction a new Hamilton mathx H is constructed [eqn.(l)] and diagonalized. E.S.R. and N.M.R. The transition probabilities between the levels inside .the specified range of the swept parameter are calculated according to the Fermi golden rule: P,, = ~Wm,6(IE,-E,I-Irv). A ( 5 ) The influence of the temperature is taken into account according to G , ( T ) = ~ , , B , , ( T ) iC. P. Keijzers et al. 3497 r . r l l l . . I I l . I I I . l l l I ~ 0 200 400 600 800 1000 1200 1400 1600 1800 2000 h Fig. 2. Part of the experimental (a) and the calculated (b) e.s.r. X-band spectrum of a powdered sample of Re’’ in TiO,. For the experimental spectrum see ref. (22); for the calculated spectrum see ref. (23). The actual spectrum is obtained from this stick spectrum by convolution with a lineshape.In e.s.r. spectroscopy it is the standard procedure that the microwave frequency is fixed whereas the external magnetic field is swept. This means that the frequency-swept spectra should be computed for a range of magnetic fields. The field-swept spectrum may then be obtained by the intersection of the frequency-swept spectra with the experimental microwave frequency. This is a very tedious procedure. Therefore, it is common practice that in case of a small sweep range the spectrum is calculated for a fixed magnetic field. We improved this procedure by means of first-order perturbation theory. The first-order energy correction for a field differing d units from the fixed, central field is: where C is the matrix of eigenvectors of the spin-Hamilton matrix at the given central field. Resonances are found at field values for which BIG r where v is the applied microwave frequency.If the field sweep is (too) large the first-order perturbation treatment might not hold. In that case more than one central field must be used with a limited field sweep. Afterwards the calculated spectra can be joined before plotting, as was done in the spectrum of fig. 2.3498 A General Program for E.S.R., ENDOR and ESEEM A complication in calculating a field-swept spectrum can be the crossing of energy levels. If this occurs, two transitions are to be expected with the same level indices. Both transitions will be found by the program and a warning is issued. ENDOR In principle, the ENDOR (c.w. and ESE) intensities depend on e.s.r. and n.m.r.transition probabilities, and also on the balance of relaxation times (in c.w.-ENDOR) or on phase destruction relations (in ESE-ENDOR). Moreover, instrumental effects such as the impedance match of the r.f. coil may influence the observed intensities. For the ENDOR intensities an approximate procedure is followed : n.m.r. transitions are selected within the specified r.f. frequency range. The ENDOR intensity of each of these transitions is calculated as the n.m.r. transition probability multiplied by the sum of the probabilities of those e.s.r. transitions which have one energy level in common with this n.m.r. transition and which are within the excitation range of the applied microwaves: In this expression i and j label the n.m.r. transitions, whereas k and I run over all energy levels.G(w0 -aik) is the excitation lineshape function around the carrier frequency wo of the microwaves (or the microwave pulses). ESEEM The expressions which are used in MAGRES for the calculation of the ESEEM intensities are generalizations of the formulae originally derived by Mims.17. l8 For the stimulated echo sequence the modulation intensity of the n.m.r. transition i-j is computed according to (1 1) p i j = “ X i j + C 2xij,kn ‘OS (cukn ‘)I k < n where x i j , kn = Re (M& Mj*, M j k ) (13) and N is a normalization constant. z is the time between the first and the second microwave pulse. The transition moments Mik are weighed with the lineshape function associated with the excitation pulse : Mik = Mik G(w0 - Wik). (14) The indices i, j , k, n in eqn (1 1H13) run over all energy levels of the spin system within the excitation range.MAGRES recognizes three types of excitation lineshapes, G : square, Gaussian and Lorentzian. The algorithm used for the calculation of the ESEEM intensities has a complexity of N4, where N is the total spin multiplicity. The computing time may be reduced significantly by omitting the second term in eqn (1 l), which is responsible for the suppression effect. The experimental analogue of such a ‘ suppression free ’ spectrum is a two-dimensional ESEEM spectrum integrated over the z dimension. MAGRES can calculate ESEEM spectra with and without the suppression effect. In fig. 3 and 4 examples are presented of experimental and calculated 14N-ESEEM spectra of a single crystal and of a powdered sample.Furthermore ESEEM spectra for the two-pulse sequence can be calculated. The following frequencies and intensities will be computed :C. P. Keijzers et al. 3499 5.0 Fig. 3. Experimental and calculated 14N Fourier-transform-ESEEM spectra in the XY plane of a single crystal of Cu/Ni (mnt),. There is a three-pulse echo sequence with z = 210 ns.* In this case, apart from the n.m.r. frequencies within an electron spin-manifold, the sums and differences of n.m.r. frequencies belonging to different m, manifolds are observed. The abovementioned ESEEM spectra are all computed in the frequency domain. However, the experimental data are obtained in the time domain. In general, this time- domain spectrum is transformed to the frequency domain by means of a Fourier transformation, as in this domain the experimental information is shown more clearly.Note that the experimental and the calculated spectrum in the frequency domain do not contain the same information. This is a consequence of the spectrometer dead-time which results in the loss of the first few points after the last microwave pulse. To handle the dead-time the following procedure was implemented in MAGRES. We start with the calculation of a stick spectrum in the frequency domain, followed by a Fourier transformation to the time domain. Subsequently, the first few points are deleted in accordance with the experimental dead-time. Zero’s are added at the end of the spectrum 116 FAR 13500 A General Program for E.S.R., ENDOR and ESEEM 1 5.0 Fig.4. Experimental and simulated 14N Fourier-transform ESEEM spectra of a powdered sample of 63C~/Ni(et,dt~)2 for various values of the magnetic field.2 in the time domain to keep the number of points of the spectrum fixed. At this stage a relaxation function (equivalent to a lineshape in the frequency domain) is also included. Finally, another Fourier transformation is carried out (but now a magnitude spectrum is calculated because of the phase distortion), yielding a spectrum in the frequency domain. This final spectrum may be compared with the experimental one, because both are obtained by calculating the magnitude spectrum after the Fourier transformation to the frequency domain. This is necessary in order to take care of the phase distortions due to the dead-time.An example of the various stages of this calculational procedure is shown in fig. 5 . Powder Spectra Powders represent an important class of materials, as many interesting materials are only available in powder form. However, the e.s.r., ENDOR and ESEEM spectra of powders are difficult t o analyse, since peak assignment is almost impossible. Therefore, an important application of MAGRES is the simulation of powder spectra. For the computation of a powder spectrum, the direction of Bo is varied over a hemisphere. ThisI 0.0 1.0 2 .o 3.0 4.0 5.0 0.0 Id.0 2d.0 30.0 40.0 50.0 frequency/MHz (256 points) time/ps ( 5 12 points) J I I I I 1 0.0 10.0 20.0 30.0 40.0 50.0 timelvs (5 12 points) Fig. 5. The various stages in the simulation of a 14N Fourier-transform ESEEM spectrum on a powdered sample of Cu/Ni(dtc),.The input dataset is listed in fig. 1. (a) Calculated stick spectrum in the frequency domain. Noise on the low-frequency side is due to the limited number (ca. 2250) of integration points. This spectrum convoluted with a lineshape is one of those in fig. 4. (b) Time- domain spectrum after Fourier transformation of spectrum (a). (c) Spectrum (b) with an exponential decay and a dead-time of 800 ns. The spectrum is filled with 800 ns of zeros in order to keep the number of points fixed. (d) Fourier-transformed magnitude spectrum of (c). The exponential decay causes convolution with a Lorentzian lineshape ; the dead-time and magnitude calculation cause lineshape deformations. w wl E33502 A General Program for E.S.R., ENDOR and ESEEM is accomplished by dividing a number of integration points over a spiral-like curve, which starts at the ‘equator’ of the hemisphere and ends on its ‘pole’.The distance between the points is kept as constant as possible. For each orientation of Bo all directions of B, perpendicular to B, should be considered. However, in order to save computer time, a random distribution of directions of B, perpendicular to B, is used. Provided that enough integration points are used, this should be a valid approximation. For each of the integration points the spin-Hamilton matrix is set up and diagonalized and the transition probabilities are calculated. The computed stick spectra are accumulated. After the last integration point the total stick spectrum can be convoluted with a lineshape and a plot of the powder spectrum may be obtained.The total stick spectrum can be saved on file in order to permit the user to try various lineshapes without recalculating the spectrum. Examples of powder e.s.r. and ESEEM spectra are shown in fig. 2, 4 and 5. Limitations and Perspectives In its current form the program MAGRES calculates the eigenvalues and eigenfunctions by means of diagonalization. Although this method requires considerable computing time and computer memory it has the important advantage of being general and applicable to any (orbitally non-degenerate) spin system. With the current mainframe computer (NAS 9060) spin systems with a total spin multiplicity N z 300 may be studied. The time-limiting step for the spectral simulations is the calculation of the transition moments.This step has a complexity of P. The necessary computer-memory increases with P. The requirements of the ESEEM simulations are even higher as the complexity is of the order N4. The requirements for computer time and memory may be reduced by applying perturbation treatments. However, to keep the program applicable to a general spin system it is then necessary to develop an algorithm that is capable of deciding whether a perturbation treatment is allowed and, if so, for which interactions. This stage has not been reached yet. In the present stage of the program, powder spectra may only be simulated: they cannot be used for the optimization of tensors. In order to achieve optimization possibilities, the calculation of the powder spectra (i.e.the integration over the sphere) must be accelerated, because in one optimization run the spectrum must be calculated very often (depending on the accuracy of the initial guess for the tensors). A new algorithm is under development. For graphical display of the simulated spectra, the program itself does not offer facilities. It will only dump the calculated intensities on disk, from where they can be picked up for input in a standard graphical package (for instance, SAS/GRAPH” or DISSPLA~,). As far as portability is concerned: the program is used under (and partly written for) the IBM operating system VM/CMS. Among other system subroutines it uses routines from the NAG-library2’ for diagonalization and Fourier transformation.In practice this means that at this moment in time, the program is not portable. However, with the rapid development of network facilities (EARN, BITNET) we are of the opinion that using these communication facilities has advantages over the development of a portable version, which would need regular updating. This implies that input datasets are sent over to our computer centre, where the program is run, and afterwards the output is sent back to the user. An extensive manual for the program MAGRES is available (in English).C. P. Keijzers et al. 3503 References 1 See, for instance, the series Electron Spin Resonance (Specialist Periodical Reports, The Royal Society 2 E. J. Reijerse, N. A. J. M. van Aerle, C. P. Keijzers. R. Boettcher, R.Kirmse and J. Stach, J. Magn. 3 R. Boettcher, R. Kirmse, J. Stach, E. J. Reijerse and C. P. Keijzers, Chem. Phys., 1986, 107, 145. 4 E. J. Reijerse, A. H. Thiers, R. Kanters, M. C. M. Gribnau and C. P. Keijzers, Inorg. Chem., in 5 D. Snaathorst, H. M. Doesburg, J. A. A. J. Perenboom and C. P. Keijzers, Znorg. Chem., 1981, 20, 6 D. Snaathorst and C. P. Keijzers, Mol. Phys., 1984, 51, 509. 7 M. A. Hefni, N. M. McConnell, F. J. Rietmeijer, M. C. M. Gribnau and C. P. Keijzers, Mol. Phys., 8 J. S. Wood, C. P. Keijzers, E. de Boer and A. Buttafava, Inorg. Chem., 1980, 19, 2213. 9 G. van Kalkeren, C. P. Keijzers, J. S. Wood, R. Srinivasan and E. de Boer, Mol. Phys., 1983, 48, 1. 10 M. L. H. Paulissen and C. P. Keijzers, J . Mol. Struct., 1984, 113, 267. I 1 J. B. A. F. Smeulders, M. A. Hefni, A. A. K. Klaassen, E. de Boer, U. Westphal and G. Geismar, 12 C. P. Keijzers, G. Zwanenburg, J. M. Vervuurt, E. de Boer and J. C. Krupa, J . Phys. C, in press. 13 P. T. Manoharan, J. H. Noordik, E. de Boer and C. P. Keijzers, J . Chem. Phys., 1981, 74, 1980. 14 0. Takizawa, R. Srinivasan and E. de Boer, Mol. Phys., 1981, 44, 677. 15 M. C. M. Gribnau, R. Murugesan, H. van Kempen and E. de Boer, Mol. Phys., 1984, 52, 195. 16 F. James and M. Roos, MINUITS, CERN, Geneva, program no. D-506. 17 W. B. Mims, Phys. Rev. 3, 1972, 5, 2409. 18 W. B. Mims, Phys. Rev. B, 1972, 6, 3543. 19 SAS/GRAPH : Statistical Analysis System, SAS-Institute Inc., Cary, North Carolina. 20 DISSPLA : Display Integrated Software System and Plotting Language, Integrated Software Systems Cooperation, 198 1, San Diego, California. 2 1 NAG : Numerical Algorithms Group, 1984, Oxford. 22 M. Valigi, D. Cordischi, D. Gazzoli, C. P. Keijzers and A. A. K. Klaassen, J. Chem. SOC., Faraday Trans. I, 1981, 77, 1871. 23 E. J. Reijerse, P. Stam, C. P. Keijzers, M. Valigi and D. Cordischi, J. Chem. Soc., Faraday Trans. 1, 1987, 83, 3613. of Chemistry, London), for extensive literature reviews on various topics. Reson., 1986, 67, 114. press. 2526. 1986, 57, 1283. Zeolites, in press. Paper 71727; Received 22nd April, 1987

ISSN:0300-9599    

DOI:10.1039/F19878303493

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J . Chem. Soc., Faraday Trans. I, 1987, 83 (12), 3505-3512 Interpretation of Electron Spin-echo Modulation for Copper(r1) Complexes in Crystalline Powders Michael W. Anderson? and Larry Kevan" Department of Chemistry, University of Houston, Houston, Texas 77004, U.S.A. A strategy is outlined for the interpretation of electron spin-echo modulation (ESEM) for copper(I1) complexes in crystalline powders. A rigorous treatment is presented for the echo intensity for signals exhibiting large g-anisotropy. This leads to many variables which influence the observed ESEM patterns, making analysis of the data difficult. Two approaches are presented to tackle this problem. (1) One can choose a system for which many of the variables are already known through complimentary techniques such as X-ray crystallography.(2) In some instances for deuterium modulation from deuterated organic ligands or D,O the nature of the complex allows the use of a spherical-averaging approximation. This approximation ignores g anisotropy and assumes all interacting nuclei to be equivalent, thus simplifying the problem greatly. Electron spin-echo modulation (ESEM) spectroscopy is a powerful tool for the measurement of weak hyperfine interactions that are often not observed in continuous- wave electron spin resonance (e.s.r.) owing to various line-broadening processes.'-4 Analytical expressions have been derived which describe in detail the nature of this hyperfine interaction for (i) S = 5, I = !j2 and (ii) arbitrary nuclear spin.5 For this discussion quadrupolar interactions will not be addressed as they are negligible for many of the systems of interest.For an isotropic e.s.r. signal the analytical expressions relate the depth of the modulation to the number of interacting nuclei, N , the electron-nuclear distance, Y, the isotropic hyperfine couping, a,, and the angle 6' between Y and the field H,, (see fig. 1 for the geometry). The total echo intensity for a paramagnetic centre interacting with N nuclei ( is given by In this case the values ri, and gi are all constants for a particular orientation of a crystal in the magnetic field. In the case of a crystalline powder 6' is no longer fixed and may take up all orientations. It is necessary, therefore, to calculate the 9-averaged echo where $ is the azimuthal angle between the z , x-plane and the z , H,,-plane as shown in fig.1. The term fl Vmod(6'J in eqn (2) indicates that there is a geometrical correlation between the interacting nuclei. This will be the case if the nuclei are part of mole- cules that are directly coordinated to the copper(I1) ion, such as the hydrogens in [Cu(H,0),I2+. However, in the case of a frozen solution there will very often be no such geometrical correlation between nuclei. To treat this case Kevan et aL6 introduced 7 Present address : Department of Chemistry, University of Connecticut, Box U-60, Storrs, CT 06268, U.S.A. 35053 506 X' ESEM of Copper( 11) Complexes Z Fig. 1. Vector diagram showing the relationship between internuclear vector r and the field H, for the case of isotropic g tensor.a ' spherical-averaging approximation ' which assumes an effective interaction distance for N nuclei randomly distributed on a sphere of radius r . This allows the integration to be performed before the product over all nuclei as in the equation (3) ( Vm0,JN = ( &ln I: Vmod(8) sin 8 dodo . r This expression is extremely useful because it allows for an easy determination of the values of r, N and a, without knowing the specific geometrical structure. It has also been shown' that for certain situations, nominally r > 0.4 nm and N > 4, that eqn (2) and (3) are equivalent. Therefore, it has been possible to treat a large number of systems, both correlated and non-correlated, by using the spherical-averaging approximation. In the case of copper(I1) ion complexes in crystalline powders another variable must be added to the interpretation, that of g anisotropy. Much interest has been shown recently in the application of ESEM techniques to the study of Cu2+ complexes in ~eolites.~*'l Here the CU" ion acts as a potential catalytic centre, while the zeolite is a microporous substrate which provides the opportunity for shape-selective catalysis.In such systems the e.s.r. signals for Cu2+ are typically axially symmetric and have a linewidth of ca. 600 G. In an ESEM experiment the microwave pulses are typically of 40 ns duration,12 which at H, = 3150 G cover only ca. 18 G. For 600 G wide e.s.r. lines this means that only a small fraction of the spins are being excited. Using the expressions hv = gpH (4) and ( 5 ) where 8, is the angle between H, and the g,, direction, for Ho = 3 150 & 9 G we calculate 8, = 90+4".In this example 3150 G corresponds to g,. The situation is illustrated in fig. 2. Here g , , is taken to be along the z-axis with r in the x, z-plane at an angle 8, to the z-direction. H,, is inclined at an angle 8, = B",+6 to the z-axis. In the above example 8; = 90" and 6 = 4", but in fig. 2 both 8, and 6 have arbitrary values. Finally is the azimuthal angle between the z, r-plane and the z, H,-plane. Because the system has axial g symmetry the angle may take all orientations. Hence, Ho may take any orientation in an annulus cut from a sphere described by the angles 0 < < 271,S;-S < 8, < 8;+ 6. g2 = g , cos2 8, + 82, sin2 8,M. W. Anderson and L.Kevan 3507 Fig. 2. Vector diagram showing the relationship between the external field H,, and internuclear vector r for the case of an axially symmetric g tensor. The diagram is drawn in the g tensor reference frame. The average modulation is then given by expressing the echo intensity in terms of O,, O0, $12,12 and averaging over the annulus described above as in the equation Eqn (6) only describes interaction with one nucleus. For N nuclei either a ~orrelated’~ or a non-correlated expression may be chosen which requires performing the product before the integration or vice versa, respectively. Clearly there are many more variables involved to calculate the ESEM modulation with axial g symmetry. Indeed there are so many variables that if nothing is known about the system and all parameters are varied independently it is unlikely that a unique solution will result.There are two possible courses of action: (i) choose a system where some of the variables are known or (ii) try to simplify eqn (6) by determining which variables, if any, are most dominant. An example of each approach follows. (i) Cu2+ Location in Zeolites Na-A and K-A A study was made of the Cu2+ cation location in Cu2+-doped zeolites Na-A and K-A by partially exchanging the zeolites with Cs+ cations and monitoring the Cs modulation by ESEM. A zeolite is a microporous, crystalline aluminosilicate with the general formula M~~n[(A102), (Si02)Jz- - wH,O, where M is an exchangeable cation.’* These cations reside in well defined crystallographic locations, some of which are shown in fig.3. It is known from X-ray diffraction that in Cs+-exchanged zeolite A the caesium cations are located at site S5 in the middle of the zeolite eight-ring. Fig. 3 shows Cs+ sites S5 of cubic zeolite A which sites can be thought of as being at the centre of the faces of a cube of edge length 1.21 nm. Fig. 4 shows this face-centred cubic arrangement of Cs+ cations. After doping a Cs+-exchanged zeolite with Cu2+ the Cu2+ cation resides somewhere on the triad axis of the cube corresponding to one of the cation sites S2’, S2 or S2*. These positions are all close to a six-membered zeolitic ring. This is a well defined3508 ESEM of Copper(@ Complexes Fig. 3. Crystal structure of zeolite A showing cation positions. Site S2 is at the centre of a six-ring face with sites S2' and S2* displaced into and out of the b-cage along the triad axis, respectively.Site S3 is adjacent to a four-ring in the a-cage while site S5 is at the centre an eight-ring in the a-cage. Fig. 4. Schematic representation of the distribution of Cs' cations in zeolite A located at the centre of the faces of a cube of edge length 1.21 nm. The Cu2+ cation is located somewhere on the body diagonal. a, Cs+; 0, Cu2+. system. The number of interacting Cs+ cations, N , is known. For a given position of the Cu2+ cation along the triad axis the values of Y and 8, for each interacting nucleus may be determined. The isotropic hyperfine, constant, a,, will be zero owing to the large values of r, greater than 0.5 nm. Finally 6, can be estimated from the position of irradiation of the e.s.r.line. Using all this information it is possible to solve eqn (6) for a fully correlated ~ystem.'~ Fig. 5 shows the theoretical Cs modulation for Cu2+ locatedM . W. Anderson and L. Kevan 3 509 1 0.8 I I I I I I I I I 1 I 0 1 2 3 4 5 TIP s Fig. 5. Theoretical three-pulse ESEM spectra showing Cs modulation for Cu2+ cation located on the triad axis near site S2 and interacting with three nearest-neighbour caesium cations. (a) 0.1 nm into a-cage. (b) 0.05 nm into a-cage. ( c ) S2. (d) 0.05 nm into P-cage. (e) 0.1 nm into 8-cage. at various cation locations. The technique, in this case, is sensitive to Cu2+ displacements of 0.02 nm. (ii) Cu2+ Cation-Adsorbate Interactions in Zeolites One primary concern in studying zeolite systems is to understand how potential reactant absorbates interact with a metal cation catalytic centre.Information may be gleaned from ESEM measurements by adsorbing deuterated species and monitoring the deuterium modulation in the three-pulse ESEM spectrum. First, consider the problem of D20 adsorption. Several different hydrated cupric complexes are possible in zeolites as shown in fig. 6. One example is an octahedrally coordinated hexa-aquo complex with two axial ligands and four equatorial ligands. The water is coordinated through the oxygen with the D-O-D plane containing the ligand axis and at room temperature it can rotate freely about the ligand axis. Then, for the equatorial ligands 8, = 90 k 16" and for the axial ligands 8, = 16kO" [see fig. 6(a)]. The range of 8, is determined from the geometry of the water molecule and a Cu2+-0 distance of 0.21 nm, assuming that the water molecule is frozen randomly into various orientations at 4 K, which is the temperature for recording the ESEM spectra.Here is a situation which is even more complex than depicted by eqn (6) because another integration has to be performed over the variation in 6,. If y1 < 6, < y2 then eqn (6) is modified to Eqn (7) was used to calculate the ESEM modulation expected when N = 8, Y = 0.28 nm, a, = 0.2 MHz for the equatorial deuteriums and N = 4, r = 0.28 nm, a, = 0 MHz for3510 ESEM of Copper(rr) Complexes Fig. 6. Schematic representations showing various hydrated Cu2+ complexes that exist within zeolite structures : (a) hexa-aquo complex with no coordination to the zeolite lattice, (b) octahedral complex coordinated to three water molecules and three lattice oxygens of a zeolite six- ring, (c) trigonal-bipyramidal complex, ( d ) square-based pyramidal complex and (e) tetrahedral complex.the axial deuteriums. The calculated ESEM pattern is shown in at the top of fig. 7. The lower two spectra in fig. 7 show two simulations based on the spherical-averaging approach described by eqn (3), treating the spectrum at the top of fig. 7 as experimental data. The two fits are with N = 12, r = 0.28 nm, a,, = 0.3 MHz and N = 10, r = 0.27 nm, a, = 0.3 MHz. Note that the spherical-averaging approximation gives a reasonable estimate to the number of interacting water molecules and the Cu2+-D distance.Although the fits are not precisely the same between the two approaches, the spherical- averaging approximation is accurate enough to determine direct coordination to either five or six water molecules. Then with additional information such as the values of g , , , g,, A , , and A,, and also the behaviour of the e.s.r. signal with temperature, the choice between fivefold and sixfold coordination should be possible. The value of a, obtained with the spherical-averaging approach is largely a fitting factor and should not be considered as being particularly physically significant. In the light of this apparent appropriateness of the spherical-averaging approach,M. W. Anderson and L. Kevan 0.6 c 351 1 (I( I - 01 I " ' I " 1 ' 1 0 1 2 3 4 5 TIP s Fig. 7. Calculated three-pulse ESEM spectra showing deuterium modulation for a hexa-aquo Cu2+ complex.(a) and (b) are simulations calculated using the spherical-averaging approximation with Y = 0.29 nm and a, = 0.3 MHz: (a) N = 10, (b) N = 12. (c) is calculated using eqn (7) with two sets of nuclei with the parameters: 8, = 83 7"; N = 8, r = 0.28 nm, a, = 0.2 MHz, 8, = 90+ 16"; N = 4, Y = 0.28 nm, a, = 0.0 MHz, 8, = 16kO". similar comparisons were made for the other hydrated complexes shown in fig. 6 . It was found that good agreement between the rigorous approach of eqn (7) and the spherical- averaging approach depends on several factors : (i) irradiation should be near g,, (ii) the electron-nucleus distance r should be greater than 0.35 nm and (iii) if r < 0.35 nm then either N should be 6 or 8, should be greater than ca.45". When 8, < 45", N < 6 and r < 0.35 nm then the spherical-averaging approximation should be used with caution. In the case of adsorbed deuterated organics, such as CD,OH, CH,CD,OH, C,D, and C,D,, the first criterion of r > 0.35 nm is usually met and therefore the spherical- averaging approximation is a good approach to use. Conclusions The appropriate method to use to interpret ESEM spectra of Cur' ion complexes in crystalline powders is a function of the system under consideration. If a complete and rigorous analysis of the data can be performed, usually when some geometrical information about the system is already known, then this is the best procedure. If little is known about the geometry of the system there are instances when a spherical- averaging approach may be adopted.For deuterium modulation the necessary criteria which should be met are (i) irradiation near g,, (ii) r > 0.35 nm, (iii) if r < 0.35 nm then either N > 6 or 8, > 45". Fortunately, in the case of most organic adsorbates r > 0.35 nm and analysis of the data can be done validly with a spherical-averaging approximation. This work was supported by the Robert A. Welch Foundation, the National Science Foundation and the Texas Advanced Technology Research Program. References 1 L. Kevan, in Time Domain Electron Spin Resonance, ed. L. Kevan and R. N. Schwartz (Wiley- Interscience, New York, 1979), chap. 8.3512 ESEM of Copper(II) Complexes 2 L. G. Rowan, E. L. Hahn and W. B. Mims, Phys. Rev. A, 1965, 137, 61. 3 V. F. Yudanov, Y. A. Grishin and Yu. D. Tsvetkov, J. Struct. Chem., 1975, 16, 694. 4 W. B. Mims, in Electron Paramagnetic Resonance, ed. S . Geschwind (Plenum Press, New York, 1972), 5 S. A. Dikanov, A. A. Shubin and P. N. Parmon, J. Magn. Reson., 1981, 42,474. 6 L. Kevan, M. K. Bowman, P. A. Narayana, R. K. Boeckman, V. F. Yudanov and Yu. D. Tsvetkov, 7 M. Narayana and L. Kevan, in Proc. 6th Int. Zeolite Conf., ed. D. Olson and A. Bisio (Butterworth, 8 M. W. Anderson and L. Kevan, J. Phys. Chem., 1986, 90, 3206. 9 M. Narayana and L. Kevan, J. Chem. SOC., Faraday Trans. 1, 1986, 82, 213. 10 T. Ichikawa and L. Kevan, J. Am. Chem. Soc., 1983, 105,402. 11 L. Kevan and M. Narayana, in Intrazeolite Chemistry (Am. Chem. SOC. Symp. Ser.), 1983, 218, 283. 12 M. W. Anderson and L. Kevan, J. Phys. Chem., 1986, 90, 6452. 13 M. W. Anderson and L. Kevan, J. Phys. Chem., 1987, 91, 2926. 14 R. M. Barrer, Zeolites and Clay Minerals (Academic Press, New York, 1978). chap. 4. J . Chem. Phys., 1975, 63, 409. London, 1984), p. 774. Paper 71639; Received 10th April, 1987

ISSN:0300-9599    

DOI:10.1039/F19878303505

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. SOC., Faraday Trans. 1, 1987, 83( 12), 3513-3525 An Electron Spin Resonance Study of Complexes of Oxovanadium( ~ v ) with Simple Dicarboxylic Acids Donald B. McPhail and Bernard A. Goodman* The Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB9 2QJ, Scotland The pH-dependent formation and stability of a range of oxovanadium( ~ v ) dicarboxylic acid complexes have been studied by e.s.r. spectroscopy. The results from oxalic acid [(CO,H),] and malonic acid [CH2(C02H)2] com- plexes show that there is significant stabilization with respect to oxovanadium( IV) oxidation/hydrolysis, in agreement with published work using electrochemical techniques. This behaviour can be explained by che- late formation, the five-membered chelate ring with oxalate being a slightly more favoured arrangement than the six-membered ring with malonate, where evidence of distortion is seen in the spectral parameters.Addition of further CH, groups in succinic acid [(CH,),(CO,H),] and glutaric acid [ ( CH2)3(C02H)2] results in corresponding decreases in complex stability, with the latter giving results similar to those obtained with fumaric aeid [ trans-(CH),(CO,H),], where no chelation is possible. With maleic acid [c~s-(CH)~(CO,H)~] a range of complexes is seen, and these have a sig- nificantly greater stability range than was observed with succinic acid. Vanadium is a trace element that is often found in biological systems, but it is not clear to what extent it is an essential micronutrient in many of the species in which it occurs.Indeed, little is known about its chemical forms and the metabolic pathways in which it is involved. The chemistry of the vanadium(1v) oxidation state, which has a single 3d electron, can be conveniently and sensitively investigated by e.s.r. spectroscopy and we have previously observed the formation of low-molecular-weight complexes of oxovanadium(1v) in the marine organism Ascidia mentula' and in the roots of wheat plants that had been exposed to high levels of vanadium.2 Others have monitored the reduction of vanadate(v) to oxovanadium( IV) in animal system^.^,^ A great deal of effort has been devoted to investigating the bonding of oxovanadium( IV) in high-molecular- weight species, such as proteins5-' and humic substances:-12 which are high-molecular- weight organic polymers extractable with alkali from soils and related materials, in which it has been shown that vanadium has a widespread occurrence.One of the principal objectives in these papers has been the identification of the nature of the coordination sites for the vanadium. In most cases this has been achieved by relating the isotropic g and A(5'V) values to the coordination environment of the vanadium. Examples of such relationships have been published by Dickson et al.,13 who showed that, for a series of model complexes in fluid solution, the e.s.r. parameters were grouped according to the nature of the atoms coordinated to the vanadium. However, the chemical nature of complexes in solution is often pH-dependent and we have recently shown in studies of simple copper peptides that a considerable range of e.s.r.parameters can be observed for similar coordinating atoms. l4 Consequently, we have now embarked on a series of experiments designed to investigate more fully the extent to which the coordination environment of vanadium can be deduced from its e.s.r. parameters. In this first paper, complexes with a group of six dicarboxylic acids are considered. These are oxalic [ (CO,H),], malonic [ CH2(C02H),], succinic [(CH2),(C02H),], glutaric [(CH2),(C02H),], maleic [Z-(CH),(CO,H),] and fumaric 35133514 Complexes of Oxovanadium ( IV) with Dicarboxylic Acids [ E-(CH),( C02H)2] acids. In each case, coordination to the vanadium is only possible via carboxylate groups, but the structures are such that there are considerable differences in the sizes of chelate rings that may be formed.The stabilities of these chelates are likely to be strongly dependent on ring size, but information is only currently available in the literature for the oxalic and malonic acid complexes of oxovanadium(~v).~~ Therefore, a further objective of the present work is to investigate the stabilities of the oxovanadium( IV) complexes with the other organic acids. Experimental The oxovanadium( IV) ion readily undergoes hydrolysis in aqueous solutions, leading to polymerization and oxidation,16 with the result that ca. 95% of the e.s.r. signal strength is lost between pH 4.5 and 5 and no signal is seen at pH > 6.17 In order to minimize the effects of such reactions in the present experiments a large (100-fold) excess of organic acid was used throughout.Solutions were prepared which were 1 mmol dmP3 in VOSO, (BDH, Laboratory Reagent) and 100 mmol dm-3 in one of the six dicarboxylic acids; oxalic, malonic, succinic, glutaric (all BDH, AnalaR), fumaric (Sigma Chemical Co.) or maleic (May and Baker). The pH of the resulting solutions was lowered to ca. 2.0 using HC1. E.s.r. spectra were obtained, both as fluid and frozen solutions (ambient temperature and 77 K), over a range of pH values which were systematically increased by the addition of KOH solutions until the e.s.r. signal was no longer observed. A few drops of methanol were added to solutions before freezing to help form a good glass in order to maximize the resolution of the solid-state spectra. All spectra were obtained with a Varian El04 X-band (ca.9.5 GHz) spectrometer. Fluid-solution spectra were recorded within 30 min of pH adjustment as both first and second derivatives of the absorption, the latter to optimize resolution of the components. A capillary tube containing a solution of Fremy's salt (potassium nitrosodisulphonate), which has g = 2.0054 and A( 14N) = 1.40 mT," was attached to the fluid-solution cell to provide an internal calibration standard. Frozen-solution spectra were obtained as the first derivatives of the absorptions. Unfortunately, it was not possible to use, in conjunc- tion with the liquid-nitrogen Dewar, a calibration method similar to that used in the fluid-solution work. Calibration had to be carried out when the sample was not in position, thus reducing accuracy of the g-value measurements at low temperature.The isotropic parameters, g and A, from the fluid-solution spectra were calculated using the following expressions: (1) Ho = H + A m + ( A 2 / 2 H ) [ I ( I + 1) - m2] - ( A 3 m / 4 H 2 ) [ 2 1 ( I + 1) - 2 m 2 - 13 and where H is the experimental magnetic field, Y the experimental microwave frequency, I the nuclear spin, m the nuclear energy levels, with integer values from -I, to, I, h is Planck's constant and p the Bohr magneton. Inclusion of the third-order term in eqn ( 1 ) was found to be essential to give an accurate description of the experimental data. Parameters for the powder spectra were obtained through computer simulation, solving the Hamiltonian for a situation of axial symmetry, the positions of the peaks for the transition (M, m ) - ( M - 1 , m ) being given by the expression'' hv = G+ A m [ 1 + (AllA:/2A2G)(2M - l ) ] + ( Ai + A2) ( A:/4A2 G)[ I ( I + 1 ) - m2] +{[(A$-A:)2/8A2G](gllg,/g2)2 sin2 28}m2 ( 3 )D.B. McPhail and B. A. Goodman 3515 Table 1. E.s.r. parameters in the various species observed in the reaction of V'" with various organic acids (see text for further details) oxalate 10.50 1.946 10.2 1.946 10.1 1.944 10.9 11.4 1.939 11.2 1.938 11.1 1.942 10.9 1.946 11.4 1.939 11.2 1.942 11.2 1.943 11.4 1.936 11.0 1.941 10.7 1.942 10.6 10.4 11.4 1.942 11.3 8.9 malonate succinate glutarate maleate fumarate 6.7 6.4 6.5 A B C" 2-9 2-9 8-9 1.968 1.98 1 1.965 18.8 1.982 not resolved 18.3 1.977 18.5 1.977 not resolved A B 3-8 3-7 1.969 1.967 1.966 1.966 1.966 1.969 19.5 1.982 19.2 1.980 19.2 1.980 18.7 7.2 6.9 7.0 A B C D" 7.6 7.1 A B C 2-3 4 5 1.966 1.967 1.966 20.1 1.98 1 19.5 1.983 19.4 20.05 1.98 1 19.5 1.982 18.9 7.4 7.1 A B C D" E" 2-3 2-4 5 6 7 1.967 1.966 1.966 1.967 1.968 A B 3-4 4- 5 1.966 1.967 19.4 1.983 not resolved 7.1 Errors are within *0.001 for giso, k0.002 for gll and g,, k0.05 mT for Aiso and *O.l for All and A, except for a, for which parameters are less accurate.where G = gPH g2=fgicos2 8+g:sin2 8 A2 = (giAi cos2 8 + g:A: sin2 8 ) / g 2 and 8 is the angle between the magnetic field and the principal axis of the complex. The 11 and 1 subscripts refer to the situations when the magnetic field is 11 and I, respectively, to the principal axis of the complex.Although this was adequate in most cases, some spectra exhibited splitting in the perpendicular region into the x and y components. In these situations, the program was only of use in obtaining parameters for the parallel components. Results In this section the results are considered systematically for each organic acid and e.s.r. spectral parameters for the various components are presented in table 1.3516 Complexes of Oxovanadium ( IV) with Dicarboxylic Acids Fig. 1. Second-derivative e.s.r. spectra at ambient temperature of a solution containing oxovanadium( IV) sulphate ( 1 mmol dm-3) and oxalic acid ( 100 mmol dm-3) at ( a ) pH 2.2, ( b ) pH 8.0 and ( c ) pH 9.0. Vertical dashed lines indicate the positions of the rn, = 5/2 transitions for species A, B and C (see text and table 1).The central triplet is from Fremy’s salt, which was used as an internal standard. Oxalic Acid In fluid solution, essentially identical spectra are observed through the pH range 2.2-7.0 and, as illustrated in fig. 1 ( a ) for the pH 2.2 sample, they consist of two components, A and B, in a ratio of ca. 25 : 1. At pH 8.0 these two species are still present in a similar ratio, although the spectral intensity has dropped to ca. 50% of its original value and there is evidence for the presence of a third component, C [fig. l ( b ) ] , which assumes a significant role at pH 9.0 [fig. l ( c ) ] . Spectral intensity at pH 9.0 is only ca. 6-7% of its value at pH 8.0, and no absorption is observed at pH B9.0. Spectra from frozen solutions are similar for the pH range 2.2-8.0 [e.g.fig. 2 ( a ) ] and are consistent with the presence of a single component, which is almost certainly species A. There was no resolution of peaks which might correspond to species B, although this is not surprising, considering its minor contribution to the fluid-solution spectra. At pH 9.0 only one component is resolved [fig. 2( b ) ] , there being no peaks corresponding to species A, despite its accounting for at least 50% of the area in the fluid-solution spectrum at this pH. Malonic Acid Two components are present in the fluid-solution spectra over the complete pH range for which results were obtained. At pH 3.0 the two species, A and B are present in a ratio of ca. 2: 1 [fig. 3 ( a ) ] , which increases to ca. 8 : 1 at pH 4.0 [fig. 3 ( b ) ] and then remains roughly constant to pH 8.0 [fig.3 ( c ) ] . The overall spectral intensity showedD. B. McPhail and B. A. Goodman 3517 I 1 YII 1 Y \I I 1 I I ' I 1 1 I I I ! I 25mT 1 , ' I Fig. 2. First-derivative e.s.r. spectra at 77 K of a solution containing oxovanadium( 1v) sulphate (1 mmol dm-3) and oxalic acid ( 100 mmol dmP3) at ( a ) pH 6.0 and ( b ) pH 9.0. The vertical dashed lines correspond to positions of peaks in the pH6.0 spectrum and demonstrate the shift that occurs at the higher pH. little change over the pH range 3-7, but decreased to ca. 12% of its original intensity at pH 8.0, with no absorption being observed at higher pH values. With frozen solutions similar spectra were observed over the complete pH range 3.0-8.0, illustrated for the pH 3.0 and 6.0 samples in fig.4, although there was slightly poorer resolution of peaks for pH <5. The results are consistent with the presence of a single species, as evidenced by the narrow, symmetrical peaks in the parallel region of the spectrum. This species most probably corresponds to B in the fluid-solution spectra, although it is surprising that there was no evidence, particularly at pH 3.0 [fig. 4(a)] for any component that might correspond to A in solution. It is also apparent that the frozen-solution spectra do not correspond to a purely axial situation, because of the splitting of the peaks in the perpendicular region [best seen in fig. 4(b)]. Thus this species exhibits distortions in the plane perpendicular to the V=O band that were not evident with the oxalic acid complexes.Succinic Acid For pH <3 the fluid-solution spectra, with a single component having parameters g = 1.966, A = 11.4 mT, were consistent with the presence of the uncomplexed oxovanadium(rv) ion. In the pH range 3-6, the spectra showed the presence of a single component at each value, but there was a steady decrease in hyperfine splitting, and possibly an increase in g, over the pH range. The parameters obtained from each measurement have been presented in table 1 as though distinct species (A, B, C and D) exist at each of these pH values, although it is possible that there are fewer and that rapidly exchanging equilibria exist between, for example, A and D. There was little variation in spectral intensity over the pH range 3-5, but the signal strength was significantly lower at pH 6, and no spectrum was obtained at higher pH values.The spectra obtained from frozen solutions show the same general trends as those with fluid solutions, there being a decrease in A and an increase in g with increasing pH (table 1). The trends in the parameters for the perpendicular regions are not thought3518 Complexes of Oxovanadium ( ~ v ) with Dicarboxylic Acids I I ’ I ’ Fig. 3. Second-derivative e.s.r. spectra at ambient temperature of a solution containing oxovanadium(1v) sulphate (1 mmol dm-3) and malonic acid (100 mmol dm-3) at ( a ) pH 3.0, ( b ) pH 4.0 and ( c ) pH 8.0. Vertical dashed lines indicate the positions of the rn, = 5/2 transitions for species A and B (see text and table 1).The central triplet is from Fremy’s salt, which was used as an internal standard. to be significant in view of the uncertainties in the individual values, although they are consistent with the trends in the parallel parameters. Glutaric Acid The fluid-solution spectrum at pH 3.1 [fig. 5 ( a ) ] shows the presence of a single com- ponent, which is probably the uncomplexed ion. There was a steady decrease in hyperfine splitting with increasing pH in the range 3-6 and a complete loss of signal for pH >6. This behaviour is similar to that observed with succinic acid, but the range of A values is significantly smaller in the glutaric acid case (table 1). In the frozen-solution spectrum at pH 2.0 [fig. 6 ( a ) ] two components are clearly seen in both the high- and low-field regions.The major component has parameters consistent with it being the uncomplexed ion, in agreement with the fluid solution results. At pH 4.0 [fig. 6(b)] the minor component at lower pH now dominates the spectrum (species B). In the pH range 4-6 there is a decrease in A and an increase in g with increasing pH, in agreement with the observation made in the fluid solutions. Maleic Acid At least four components are resolved from the fluid-solution spectra over the pH range 2.0-7.1. The major component in the spectrum at the lowest pH [fig. 7(a)] is probablyD. B. McPhail and B. A. Goodman 3519 --4 - - I I I I " - 25 mT - Fig. 4. First-derivative e.s.r. spectra at 77 K of a solution containing oxovanadium( 1v) sulphate (1 mmol dmP3) and malonic acid (100 mmol dm-3) at ( a ) pH 3.0 and ( b ) pH 6.0.the uncomplexed ion, but the minor component, species B, at this pH dominates the spectrum at pH 3.0 [fig. 7 ( b ) ] . In agreement with the trends observed for the succinic and glutaric acids, there is a decrease in hyperfine splitting with increasing pH for pH > 3 [fig. 7( b)-( d ) ] . With maleic acid, however, the range of A values is greater than those obtained with these other acids. Although the intensity of the spectrum at pH 7.1 is only ca. 10% of those at lower pH, the fact that a spectrum is observed at all shows that the V'" exists for a complete pH unit higher in combination with maleic acid than with the two largest saturated acids that were investigated. Frozen-solution spectra are in general agreement with those obtained from fluid solutions. At pH 2.0, two components are observed [fig.8 ( a ) ] in roughly comparable ratios to their existence in fluid solution and the spectrum at pH 3 [fig. 8( b ) ] is analogous to the minor component at pH 2.0. Raising the pH resulted in steady decreases in All and increases in gll (table l ) , although a number of spectra [see e.g. fig. 8 ( c ) ] show evidence for the simultaneous presence of more than one species. Fumaric Acid. Over the pH range 3.0-5.4 there was a slight decrease in hyperfine splitting (table 1 ) in fluid solution. The signal was noticeably weaker at the higher pH value and disappeared for pH >6. Only one species was seen in the frozen solution spectra and in the solid state no resonance was obtained with a pH as low as 5.4.Discussion In acidic solutions the oxovanadium( ~ v ) ion hydrolyses with increasing pH to produce the hydrated species VO( OH)+, (VO),( OH) ;+ and VO( OH), , the last of these precipitat- ing as a hydrated oxyhydroxide. Also, oxidation to vanadium(v) occurs above pH 6.0.163520 Complexes of Oxovanadium ( ~ v ) with Dicarboxylic Acids I II I . V ’ Fig. 5. Second-derivative e.s.r. spectra at ambient temperature of a solution containing oxovanadium(1v) sulphate (1 mmol dmP3) and glutaric acid (100 mmol dm-3) at ( Q ) pH 3.1 and ( b ) pH 5.0. The vertical dashed line indicates the position of the rn, = 7/2 transition for the uncomplexed oxovanadium(1v) ion. The central triplet is from Fremy’s salt, which was used as an internal standard.E.s.r. investigations of solutions of oxovanadium( IV) in our laboratory have demonstrated that the hydrated V02+ ion has fluid-solution parameters g = 1.9673(5), A(5’V) = 11.48(2) mT and frozen-solution parameters gl1 = 1.9405, gl = 1.9835, AII(”V) = 19.80 mT and A,(”V) = 7.25 mT, which are in general agreement with published values. The corresponding values for hydrated VO(OH)+ are so similar that they are unresolvable in both fluid and frozen s01ution.l~ The other species do not produce electron spin resonance, so that only weak signals are obtained above pH5 and no spectrum is observed from solutions above a pH of ca. 6. In the presence of coordinating ligands, complexation reactions compete with hydrolysis and oxidation, leading to an extension of the pH range over which the oxovanadium(1v) ion is able to exist. The dicarboxylic acids used in the present experiment all exhibit two distinct deprotonation reactions, H2L S HL-+ H+ with typical published values for pK, and pK2 ( i e .-log K , and -log K 2 ) being given in table 2. It is clear from these numbers that there are considerable differences in the degrees of dissociation of the organic acids at the pH values of our solutions. Thus the major species for oxalic acid are H2L for pH <1.13, HL- for 1.13 <pH <4.98 and L2- for pH >4.98, whereas the corresponding values for malonic acid are, respectively, ca. 1.7 and 3.6pH units higher. It should also be noted that, in the low-ionic-strength solutions used for our e.s.r. measurements, these pH values would all be somewhat higher than predicted from table 2.Thus, with the succinic and glutaric acids, the L2- species is only dominant in solutions for pH >9 and hence will play no role in vanadium complexation, even though the solutions contain a 100-fold excess of the ligand. With malonic and maleic acids the L2- species may be important at the higher pH values, but it is only for oxalic acid that there it exists in significant amounts over a wide pH range.D. B. McPhail and B. A. Goodman 3521 Fig. 6. First-derivative e.s.r. spectra at 77 K of a solution of oxovanadium(1v) sulphate ( 1 mmol dmP3) and glutaric acid (100 mmol dmP3) at ( a ) pH 2.1, ( b ) pH 4.0 and ( c ) pH 6.1. The vertical dashed line indicates the position of the m1 = 7/2 parallel transition for species C (see text and table 1 ) .Electrochemical studies have been reported in the literature for the oxalic acid and malonic acid complexes of oxovanadium( ~ v ) . In 1 mmol dmP3 NaC104, values of log K , are 6.45 25 and 5.23,26 respectively, for the oxalic and malonic acid complexes and the corresponding values of p2 are 11.77 25 and 8.85,26 which are equivalent to log K2 values of 5.32 and 3.62, respectively. However, in view of the discussion above, it is unlikely that the same types of species are involved in each case. With oxalic acid the L2-species is probably involved in the complexation reactions, since it is the major species in solution for pH >0.45, and is present in amounts comparable to the vanadium at pH values as low as 3.Since the complexes appear to be similar over a wide range of pH range, it is unlikely that any other organic species is involved. Species A and B may, therefore, correspond to mono- and bis-complexes of V02+ with L2- and the species C, which appears at high pH, may represent a complex involving hydroxyl groups, possibly [ VO (0 H ) L] - . Of the two complexes observed with malonic acid, species A, which is dominant at most pHs, has spectral parameters that are similar to those of species C with oxalic acid. This may, therefore, represent a complex between VO(OH)+ and the ligand. The unsymmetrical nature of complex A is further supported by the frozen-solution spectra, where there is a definite distortion from axial symmetry producing non-equivalent x- and y-components.The rapid decrease in the relative contribution to the spectra of3522 Complexes of Oxovanadium ( IV) with Dicarboxylic Acids Fig. 7. Second-derivative e.s.r. spectra at ambient temperature of a solution containing oxovanadium( IV) sulphate ( 1 mmol dm-3) and maleic acid (100 mmol dm-3) at ( a ) pH 2.0, ( b ) pH 3.0, (c) pH 5.0 and ( d ) pH 7.1. Vertical dashed lines indicate the positions of the rnl = 7/2 transitions for species A, B, C and D (see text and table 1). The central triplet is from Fremy's salt, which was used as an internal standard. species B over the pH range 3-4 followed by comparatively little change from pH 4-7 suggests that this may represent a complex with V02+ and not a change in ligand dissociation. Alternatively, this species may correspond to a singly bonded ligand by analogy with the higher homologues discussed later.With regard to the nature of the ligand, the species HL- is the only one with concentrations comparable to or greater than that of the vanadium over the pH range for which complexes were observed. However, the involvement of L2- cannot be excluded since chelation with the metal could induce additional deprotonation at the ligand. The range of spectral parameters observed with the succinic and glutaric acid complexes is much smaller than those obtained with the lower-molecular-weight acids, consistent with the weaker association between the metal and ligands. With both ligands there is an increase in the proportion of HL- with increasing pH over most of the range for which spectra are observed, and this is almost certainly the form of the ligand that is bound to the metal.The existence of a component consistent with the uncomplexed oxovanadium(1v) ion to pH 3 is consistent with this conclusion, since it is only for pH >2.25 that the solution concentrations of HL- become comparable to the vanadium concentrations. Although there is also a change in composition of the vanadium species from V02+ to VO(OH)+ over the pH range 2-6, it is possible that the different spectral parameters reported in table 1 for the different pH values do not all represent distinctlyD. B. McPhail and B. A. Goodman 3523 Fig. 8. First-derivative e.s.r. spectra at 77 K of a solution containing oxovanadium( fv) sulphate ( 1 mmol dmP3) and maleic acid (100 mmol dm-3) and ( a ) pH 2.0, ( b ) pH 3.0 at (c) pH 5.0.The vertical dashed line indicates the position of the rn, = 7/2 parallel transition for species B (see text and table 1). Table 2. Acid dissociation constants for dicarboxylic acids (in 1 mol dm-3 NaC104) acid PKI PK2 ref. oxalic 1.13 3.85 20 malonic 2.847 5.696 21 succinic 4.206 5.639 22 glutaric 4.35 5.40 23 maleic 1.91 6.332 24 fumaric 3.095 4.602 24 different species. Either or both of species B and C with succinic acid, for example, could correspond to the existence of components from higher and lower pH values in equilibrium in the solutions. With maleic acid, there are significant amounts of the uncomplexed oxovanadium( ~ v ) evident in the solutions at pH2 and 3, over which pH range there is an increasing contribution from species B with increasing pH.At higher pH its intensity declines and it is absent at pH >4. It is likely, therefore, that this species corresponds to complexation3 524 Complexes of Oxovanadium ( IV) with Dicarboxylic Acids between V02+ and HL-. The species observed at higher pH almost certainly correspond to complexes of VO(OH)+, and in the pH range 5-7 there is a steady increase in the proportion of the ligand as L2- (HL- and L2- have equal concentrations at a pH of ca. 6.2). The change in parameters over this pH range probably reflects the gradual deprotonation of the ligand and not necessarily distinct species at each pH value. However, the existence of complexes to pH 7 demonstrates the stronger association of vanadium with maleic than with succinic acid, which has the same number of carbon atoms.This relative stabilization of the oxovanadium(1v) ion by maleic acid could be due to association of VO(OH)+ with the L2- ligand species to produce an anionic species that is less readily attacked by the OH- ion. However, it is more likely that a chelate is formed, since the spectral parameters in the pH range 5-7 (species C, D and E in table 1 ) are comparable to those of species seen with oxalic and malonic acids. This increased chelation ability of maleic acid compared to succinic acid could be due to the presence of the double bond, which could have the effect of decreasing angle strain within the ring system or of permitting a certain amount of conjugation, which would have the effect of increasing the interaction between the ligand and the unpaired electron on the metal.In the case of fumaric acid, which is equivalent to maleic acid except for the conformation of the carboxyl groups, there is no evidence for any strong association between the ligand and metal to form mononuclear complexes. However, the decreased stability of the e.s.r. signal with respect to increasing pH compared to the ligand-free system suggests that fumaric acid may be instrumental in the stimulation of the produc- tion of polymeric species. In general, the parameters obtained with these complexes between oxovanadium( ~ v ) and dicarboxylic acids fall within the range designated by Dickson et al. for the coordination of vanadium to oxygen ligands. The most notable exception, however, is species B in the oxalic acid system, which has parameters which would predict coordina- tion to four sulphur atoms.Clearly, this is impossible in the present situation, which probably corresponds to a bis-complex, in contrast to the mono-complexes of the other species studied. The existence of this one anomalous result suggests that there may be other exceptions to the correlations of Dickson et aL, and these will be the subject of further investigations. In the meantime, however, it is suggested that, whilst empirical correlations, such as those of Dickson et al., are of great general value, they should be used with caution, and wherever possible confirmation of conclusions should be obtained by alternative methods. Conclusions E.s.r. investigations of a range of oxovanadium( rv) complexes with dicarboxylic acids have demonstrated a clear distinction between the situations in which chelation occurs and those in which the ligand is bonded via a single 0 atom. We have concluded that in virtually every case the species responsible for the e.s.r.spectra consist of a single V atom and a single ligand molecule; the one exception being with oxalic acid where a minor component, which is thought to correspond to a bis complex, is seen over a wide pH range. This latter species produces parameters that are significantly different from those generally ascribed to complexes of oxovanadium( IV), in which the V is coordinated solely to 0 atoms. References 1 M. V. Bell, B. J. S. Pirie, D. B. McPhail, B.A. Goodman, I. B. Falk-Petersen and J. R. Sargent, J. Mar. 2 D. B. McPhail, D. J. Linehan and B. A. Goodman, New PhytoZ., 1982,91, 615. 3 H. Sakurai, S. Shimomura, K. Fukuzawa and K. Ishizu, Biochem. Biophys. Res. Commun., 1980,96,293. Biol. Assoc. UK, 1982, 62, 709.D. B. McPhail and B. A. Goodman 3525 4 I. G . Macara, K. Kustin and L. C. Cantley, Biochim. Biophys. Acta, 1980, 629, 95. 5 J. J. Fitzgerald and N. D. Chasteen, Biochemistry, 1974, 13, 4338. 6 L. W. White and N. D. Chasteen, J. Phys. Chem., 1979, 83, 279. 7 J. D. Casey and N. D. Chasteen, J. Inorg. Biochem., 1980, 13, 111, 127. 8 N. D. Chasteen and J. Francavilla, J. Phys. Chem., 1976, 80, 867. 9 B. A. Goodman and M. V. Cheshire, Geochim. Cosmochim. Acta, 1975, 39, 1711. 10 M. V. Cheshire, M. L. Berrow, B. A. Goodman and C. M. Mundie, Geochim. Cosmochim. Acta, 1977, 1 1 G. D. Templeton and N. D. Chasteen, Geochim. Cosmochim. Acta, 1980,44, 741. 12 A. L. Abdul-Halim, J. C. Evans, C. C. Rowlands and J. H. Thomas, Geochirn. Cosmochim. Acta, 1981, 13 F. E. Dickson, C. J. Kunesh, E. L. McGinnis and L. Petrakis, Anal. Chem., 1972, 44, 978. 14 B. A. Goodman and D. B. McPhail, J. Chem. Res., 1985, (S)276; (M)2901. 15 Stability Constants of Metal-ion Complexes. Part B, Organic Ligands, IUPAC Chem. Data Ser. No. 22, 16 C. F. Baes and R. E. Mesmer, The Hydrolysis of Cations (Wiley-Interscience, New York, 1976), pp. 17 J. Francavilla and N. D. Chasteen, Inorg. Chem., 1975, 14, 2860. 18 J. J. Windle and A. K. Wiersema, J. Chem. Phys., 1963, 39, 1139. 19 A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of Transition Metals Ions (Clarendon Press, Oxford, 1970). 20 K. Nagata, A. Umayahara and R. Tsuchiya, Bull. Chem. SOC. Jpn, 1965, 38, 1059. 21 D. J. G. Ives and D. Prasad, J. Chem. SOC. B, 1970, 1649. 22 C. F. Wilcox and C. Leung, J. Am. Chem. SOC., 1968, 90, 336. 23 R. H. Jones and D. I. Stock, J. Chem. SOC., 1960, 102. 24 G. Dahlgren and F. A. Long, J. Am. Chem. SOC. 1960, 82, 1303. 25 A. A. Ivakin, E. M. Voronova and L. V. Chashchina, Zh. Neorg. Khim., 1970, 12, 1, 175. 26 A. A. Ivakin, E. M. Voronova and L. V. Chashchina, Zh. Neorg. Khim., 1970, 15, 7, 1839. 41, 1131. 45, 481. compiled by D. D. Perrin (Pergamon Press, Oxford, 1979). 197-202. Paper 71728; Received 22nd April, 1987

ISSN:0300-9599    

DOI:10.1039/F19878303513

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. Soc., Faraday Trans. I, 1987, 83 (12), 3527-3533 Electron Spin Resonance Spectroscopy of Layered Chromium Silver Chalcogenides Robert E. Benfield* Chemical Laboratory, University of Kent at Canterbury, Canterbury, Kent CT2 7NH Peter P. Edwards University Chemical Laboratory, Lensfield Road, Cambridge CB2 1 E W Angelica M. Stacy Department of Chemistry, University of California, Berkelqy, California 94720, US. A . Electron spin resonance and magnetic susceptibilities of the layered superionic conductors AgCrS, and AgCrSe, have been studied between 4 and 300 K. These compounds undergo magnetic phase transitions both within and between the layers of Cr3+ ions. At 295 K, polycrystalline AgCrS, gave g = 1.982, AHpp 410 G; AgCrSe, gave g = 1.989, AHpp = 385 G. On cooling towards the respective Niel temperatures T, of 42 and 55 K, the e.s.r.linewidths diverge with critical exponents close to 0.66, typical of two-dimensional antiferromagnetic systems. Magnetic ordering between the Cr3+ layers commences more than 100 K above the Nee1 temperatures. Supercooling effects have also been observed. Some differences in the e.s.r. behaviour of the two compounds were found. The g value of AgCrSe, increased on close approach to TN from above, whereas that of AgCrS, decreased. A strong, broad resonance with a temperature-dependent g value was observed below TN from AgCrSe,, but not from AgCrS,. These effects can be related to differences in magnetic structure within the Cr3+ layers. There is little magnetic evidence for a structural phase transition reported to occur at 160 K in AgCrS,.The stoichiometric solid electrolytes AgCrS, and AgCrSe, [M'M"'X,] crystallise in the trigonal space group R3m. Sandwiches of CrX, layers contain octahedrally coordinated Cr3+ Half the tetrahedral interstices between these layers are occupied by Ag' ions, which are able to transport charge, and these compounds have potential industrial applications as superionic conductors at high temperature^.^^ AgCrS, and AgCrSe, also have interesting magnetic properties at low temperatures. Although their magnetic susceptibilities have been the subject of previous study,l only room-temperature e.s.r. spectra have been reported to date.5 We have studied these two compounds by e.s.r. spectroscopy between 4 and 300 K. Experiment a1 The compounds were prepared by literature method^.^^ Magnetic susceptibilities were measured with an S.H.E.SQUID magnetometer between 5 and 300 K in fields from 5 to 40 kG. X-Band e.s.r. spectra of powdered samples were recorded on Varian E-109 and JEOL PE-1-X instruments using 100 kHz modulation and typically 5 mW microwave power. Temperatures below 100 K were attained with an Oxford Instruments ESR-900 liquid helium cryostat, and those between 80 and 300 K using a flow of cold nitrogen gas. Sample temperatures were controlled with an Oxford digital temperature controller. DPPH was used as a g-factor standard. 35273528 E.S.R. of Layered Chromium Silver Chalcogenides ZOO] t .* * * *. *. * * i* .. * * * * 8 8 8 * * ** *.*. -0 'Ot *A 50 100 150 200 250 3d0 TI K Fig.1. Reciprocal magnetic susceptibilities of AgCrS, and AgCrSe,: +, 5; 0, 40 kG. (a) AgCrS, (afm/afm), 8 = -55 K, TN = 42 K. (b) AgCrSe, (fm/afm), B = 72 K, TN = 55 K. Results and Discussion Magnetic Structures These compounds are composed of CrX, layers with interstitial silver ions. The magnetic moments of the octahedrally coordinated Cr3+(tis) ions order with the spins lying in the plane of the layers. Within the layers, direct Cr-Cr antiferromagnetic coupling competes with indirect Cr-X-Cr ferromagnetic coupling.' Exchange parameters can be correlated with interchromium distances.s The size difference between sulphide and selenide ions causes AgCrS, to be antiferromagnetic (asymptotic Curie temperature 8 = - 5 5 K) and AgCrSe, ferromagnetic (8 = 72 K).l In both compounds, the ordering of the Cr3+ spins between layers is antiferromagnetic.This is shown by the form of their overall magnetic susceptibility curves (fig. 1) and has been confirmed by neutron diffraction., Ndel temperatures TN, determined from SQUID susceptibility measurements, are 42 K for AgCrS, and 55 K for AgCrSe,; these values are in close agreement with previous literature values.1* To denote the magnetic ordering within/between the CrX, layers, we term AgCrS, afm/afm and AgCrSe, fm/ afm.R. E. Benfield, P . P. Edwards and A . M . Stacy 4000 3200. 3 529 0 0 0 0 9 2400. d a 1600. 0 0 0 8ool 500ot an Fig. 2. E.s.r. linewidth of AgCrS,; (a) linear and (b) logarithmic plots us. temperature. Slope in (b) = -0.64. Significant deviation from linear Curie-Weiss susceptibility behaviour, demonstrating short-range magnetic order, occurs more than 100 K above TN in each compound (fig.1). Inverse susceptibility plots must therefore be extrapolated from high temperatures to obtain accurate values of the temperature-axis intercepts 8. E.S.R. Spectral Linewidths Intense, Lorentzian e.s.r. spectra were observed from both compounds above their Nee1 temperatures. At 295 K, AgCrS, gave g = 1.982, peak-to-peak linewidth AHpp = 410 G. AgCrSe, gave g = 1.989, AHpp = 385 G. These g values are typical of Cr3+ ions in an octahedral en~ironment.~ On cooling, the g values remained constant, but the linewidths diverged, following the equation : AH,, CC(T-T,)-~ with values of the exponent p close to 0.66 (fig. 2). This critical behaviour and exponent value is characteristic of two-dimensional antiferromagnetic systems according to the universality principle.lo* l1 The equation was valid for both compounds from within a few degrees of TN to more than 150 K above it, confirming the onset of magnetic ordering at high temperatures as shown by the susceptibility measurements. Other types of antiferromagnetic system obey such power laws to only a few degrees above TN.12 The linewidths of both compounds diverged to reach values over 4000 G, but within 10 K of their respective NCel temperatures they were less broad than indicated by eqn (1) (fig. 2). This tailing-off of the linewidth broadening approximately coincided with the onset of temperature-dependence of the g values and a sharp reduction in spectral3530 E.S.R.of Layered Chromium Silver Chalcogenides 2.001 1.95 g 1.90 1-65 0 t 0 0 0 0 intensities (see below). This e.s.r. linewidth divergence behaviour resembles that'3*14 of NaCrS,, which has a related structure, space group R3m, with sodium ions occupying octahedral interstices between CrS, layers.', "7 l6 The linewidths of the silver compounds greatly exceed those reported for NaCrS,. Phase Transition in AgCrS, In AgCrS,, but not AgCrSe,, a phase transition between 160 and 200 K has been reported" on the basis of X-ray powder diffraction measurements of the crystallographic c-axis and changes in diffraction line intensities. These unit cell parameters are not fully consistent with those of an earlier study,, which did not detect any phase transitions in AgCrS, other than that at 670 K associated with disordering and increased mobility of the silver ions.A phase transition at 160-200 K, altering the separation of the CrS, layers, should perturb the magnetic properties of AgCrS,, because susceptibility deviations from the intraplanar Curie-Weiss law are already apparent in this temperature range (see above). However, no effects on e.s.r. g-values or linewidth could be found in AgCrS, in this temperature range. Susceptibility and e.s.r. spectral intensity showed only barely discernible perturbations. If this phase transition exists, it has virtually no effect on the magnetic properties of the Cr3+ ions. E.S.R. Spectra Close to TN Some significant differences between the e.s.r. behaviour of AgCrS, and that of AgCrSe, were observed.The g values of both compounds remained independent of temperature until the respective Nee1 temperatures were closely approached from above. The g value of AgCrS, then decreased over a temperature range of 15 K to reach 1.87 at 42 K (fig. 3). In contrast, the g value of AgCrSe, increased from its high-temperature value (fig. 4) by a similar amount. The e.s.r. spectral intensity was calculated as the amplitude of the derivative spectrum times the square of the peak-to-peak linewidth, normalised for spectrometer gain andR. E. BenJield, P . P . Edwards and A . M . Stacy 353 1 '20 '40 'SO 'SO ioo i20 TI K Fig. 4. E.s.r. g value of AgCrSe,. applied microwave power. The intensity of the resonance from AgCrS,, which obeyed the Curie-Weiss law on cooling from room temperature, fell as TN was approached closely from above, over a range of 15-20 K.The e.s.r.signal was extinguished on passing through TN. With the exception of a resonance lop5 times as intense ( g = 2.06, AHpp = 100 G) which was assigned to a trace of Fe3+ impurity, no e.s.r. could be detected in AgCrS, below its TN. This is the usual case in antiferromagnets, because the strong internal fields greatly alter the conditions for resonance. AgCrSe, behaved differently. Although its e.s.r. spectral intensity also fell as TN was approached from above (fig. 9, a resonance was observed below TN, of intensity comparable to that observed at room temperature. The linewidth was approximately temperature-independent at 2200 f 100 G.The lineshape appeared to be Lorentzian, but its width was too high a proportion of the magnet scan for detailed verification. The g value increased on cooling, to 3.7fO.l at 4 K (fig. 4). These contrasts between the two compounds must arise from their different magnetic structures; AgCrS, is afm/afm and AgCrSe, is fm/afm. The two types of magnetic ordering lead to different internal field effects at temperatures where bulk magnetisation is important. The behaviour of AgCrSe, below its TN showed some resemblance to the antiferromagnetic resonance of NaCrS,.lg Supercooling and Hysteresis Supercooling effects were found in the e.s.r. spectra of both AgCrS, and AgCrSe,. Spectra of samples cooled rapidly to 4 K took up to several hours to equilibrate. Indications of hysteresis around the NCel temperatures were also found.This was easier to study in AgCrS, because of the greater qualitative spectral change at TN. Antiferromagnetic ordering is ideally a second-order process, which should show no hysteresis. 2o An activation energy leading to partial first-order character could arise from a volume change at TN if the separation of CrX, layers alters. The c / a ratio in both compounds is slightly smaller, at 4 K than at 300 K, and a contraction of the c-axis on 117 FAR I3532 100. 80. h v, U .- c 2 60. v x e U .* .- 2 40. 20. E.S.R. of Layered Chromium Silver Chalcogenides a @ a a a 0 a a a a 0 a a a a a a a a I a T/ K Fig. 5. Estimated e.s.r. spectral intensity of AgCrSe,. magnetic ordering seems likely ; however, differential thermal expansion along the a- and c-axes would be expected in any case in these layered materials and unit cell data are available for too few temperatures to permit the question to be resolved.Hysteresis effects in magnetic phase transitions are very complex, and may depend on crystallite size and crystal defects.,' Magnetic susceptibilities below TN were found to be field-dependent and were also affected by the sequence of fields to which the samples were exposed. Susceptibilities above TN were independent of field (fig. 1). The thermomagnetic history of the sample has been foundz2 to influence the magnetic properties of layered antiferromagnetic compounds of Fez+. Concluding Remarks AgCrS, and AgCrSe, are layered compounds which undergo low-temperature magnetic phase transitions as well as high-temperature transitions associated with the onset of superionic conduction.Their e.s.r. spectra have been studied and are found to undergo critical linewidth broadening on cooling towards their NCel temperatures ; this is characteristic of two-dimensional antiferromagnetic systems. Differences in the e.s.r. of the two compounds around their respective NCel temperatures have been found, and these have been correlated with differences in their magnetic structures. References 1 P. F. Bongers, C. F. van Bruggen, J. Koopstra, W. P. F. A. M. Omloo, G. A. Wiegers and F. Jellinek, 2 F. M. R. Engelsman, G. A. Wiegers, F. Jellinek and B. van Laar, J. Solid Stare Chem., 1973, 6, 574. 3 T. Hibma, Solid State Commun., 1980, 33, 445.4 B. A. Boukamp and G. A. Wiegers, Solid State Ionics, 1983, %lo, 1193. 5 M. Krygowska-Doniec, Acta Phys. Polon., 1978, A54, 441. 6 H. Hahn and C. de Lorent, 2. Anorg. Allg. Chem., 1957, 290, 68. 7 J. B. Goodenough, Magnetism and the Chemical Bond (Wiley-Interscience, New York, 1963), chap. 8 P. Colombet and M. Danot, Solid Stare Commun., 1983, 45, 311. J . Phys. Chem. Solih, 1968, 29, 977. 3.R. E. BenJield, P. P. Edwards and A . M. Stacy 3533 9 A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of Transition Ions (Clarendon Press, Oxford, 1970), p. 432. 10 C. N. R. Rao and K. J. Rao, Phase Transitions in Solidr (McGraw-Hill, London, 1978), chap. 5. 1 1 F. J. Owens, in Magnetic Resonance of Phase Transitions, ed. C. P. Poole and H. A. Farach (Academic 12 G. L. Witt, Physica, 1972, 61, 476. 13 P. R. Elliston, J. Phys. C , 1974, 7 , 425. 14 P. M. Richards, K. A. Miiller, H. R. Boesch and F. Waldner, Phys. Rev. B, 1974, 10, 4531. 15 J. W. Boon and C. H. MacGillavry, Recl. Trav. Chim. Pays-Bas, 1942, 61, 910. 16 W. Rudorff and K. Stegemann, 2. Anorg. Allg. Chem., 1943, 251, 376. 17 V. M. Antropov, V. G. Pleshchev, V. N. Konev and S. M. Kiskin, Fiz. Tverd. Tela, 1983, 25, 2767. 18 D. M. S. Bagguley and J. Owen, Rep. Prog. Phys., 1957, 20, 304. 19 P. R. Elliston, J. Phys. Chem. Solids, 1977, 38, 179. 20 Ref. (lo), chap. 2. 21 E. Konig, G. Ritter, W. Irler and H. A. Goodwin, J. Am. Chem. Soc., 1980, 102, 4681. 22 M. A. Semary, M. M. Abdel-Kader and M. F. Mostafa, Chem. Phys. Lett., 1983, 96, 641. Press, New York, 1979), chap. 6. Paper 7/641, Received 10th April, 1987 117-2

ISSN:0300-9599    

DOI:10.1039/F19878303527

出版商:RSC    

年代:1987

数据来源: RSC

摘要:

J. Chem. Soc., Furaduy Trans. I , 1987, 83(12), 3535-3540 The Electron Spin Resonance Spectra of CpCr( CO), and CpCr(CO),P(C,H,), in Single Crystals of their Mn Analogues John R. Morton* and Keith F. Preston* Division of Chemistry, National Research Council of Canada, Ottawa, Ontario, Canada K1A OR9 Neil A. Cooley and Michael C. Baird Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6 Paul J. Krusic and Stephen J. McLain Central Research and Development Department, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19898, U.S.A. The e.s.r. spectra of CpCr(CO), and CPC~(CO)~L, where L is P(C6H5)3 and Cp is cyclopentadienyl, have been examined in single crystals of their respective Mn derivatives. In both cases an axis (z) passing through the chromium atom and the centre of the Cp ring is the direction of maximum g, indicating that the semi-occupied orbital is predominantly xy or x2 - y 2 , where x and y are perpendicular to z.The effective symmetry in both instances is C,, with x lying perpendicular to the symmetry plane. In CpCr(CO),, x is the direction of intermediate g-factor, whereas in CpCr(C0)2L, x is the direction of minimum g-factor. The reasons for this difference are discussed in terms of the energy levels of the f & e i manifold under Oh, C3v and C, symmetries. The 53Cr hyperfine interaction in CpCr( CO), is also analysed. We have investigated the e.s.r. spectra of two paramagnetic chromium compounds which have been doped into single crystals of the corresponding diamagnetic manganese derivative.As is well known, the five 3d orbitals of a chromium atom split in octahedral symmetry into an upper pair of representation Eg in Oh, and a lower trio of representation T2g in Oh. Chromium hexacarbonyl is a stable molecule whose chromium atom has six electrons in its t2g shell. It is therefore a diamagnetic Cro compound. The molecules we shall be discussing are CpCr(CO), and CPC~(CO)~L, where L stands for triphenyl phosphine, P(C6H5)3. The first of these has a three-fold axis, and the second a plane of symmetry. One of the objectives of our study was to see what effect a lower symmetry had on the ordering of the energy levels within the t2g manifold when it splits as a result of the lower symmetry. The frontier orbitals of a cyclopentadienyl group resemble those of three CO ligands,' although the molecule CpCr( CO), is a paramagnetic Cr' compound, since Cp- is a five-electron donor only.The compound CpMn(CO), is a d6 diamagnet, entirely analogous to Cr(CO),. Like Cr(C0)6, it is a useful crystalline matrix and one which readily accepts the paramagnetic CpCr(CO), as an impurity. Experimental Single crystals of CpMn(CO), containing a fraction of a percent of the chromium analogue were grown by slowly cooling a molten mixture of CpMn(CO), and the dimer of CpCr(CO), . The dimer appears to be slightly dissociated at 80 "C and a very small 35353536 E.S.R. Of CpCr( co3) and CpCr( CO)*P( C6H5)3 amount of the monomer enters the crystals of CpMn(CO), as they form. CPM~(CO)~L crystals containing the corresponding paramagnetic chromium compound were grown by slow evaporation of a solution in hexane at -40°C. The crystal structures of both host matrices are known: CpMn(CO), is monoclinic ( P ~ J u ) , ~ CpMn(C0)2L is triclinic (Pi)., With the help of X-ray diffraction methods several crystals of each compound were oriented and cemented into 4 mm 0.d.e.s.r. tubes. The axis systems chosen were as follows: for CpMn(CO), the a, b, c" axes; for CPM~(CO)~L the a*, b", c axes.4 Crystals were oriented so that for each sample one of the axes lay parallel to the length of the tube, and the directions of the other two were identified by small flags. The e.s.r. spectra of the chromium-doped crystals were examined at 77 or 20 K with a Varian E-12 spectrometer equipped with devices for measuring the magnetic field and the microwave frequency.The tubes in which the crystals were contained could be rotated about a vertical axis, so that the magnetic field Ho of the spectrometer explored a horizontal plane. The g 2 and 53Cr or 31P hyperfine tensors were assembled by least-squares fitting a sinusoidal curve to the set of data points obtained in the ij plane: g 2 ( 0 ) = gf cos2 o + gi sin2 o + g$ sin 20. Thus g$ is positive if g2(0) has a maximum and negative if it has a minimum in the quadrant contained by Ho parallel to + i and +j. In the case of the monoclinic crystal CpMn(CO), it was necessary to examine the spectra for skew directions in order to determine the relative signs of the off-diagonal elements g;b and gbc*. Hyperfine interactions of the central 53Cr nucleus of CpCr(CO), were obtained in a similar way.The 53Cr nucleus has a natural abundance of 9.5%, and a spin of 1.5. The spectrum of CpCr(CO), was sufficiently strong that the outside lines of the four-line manifold due to the 53Cr isotope could readily be detected in natural abundance. Hyperfine interactions of the 13C nuclei of the carbonyl ligands were also detected. The 31P hyperfine interaction of CpCr( C0)2P( C6H5)3 was investigated, but found to be virtually isotropic and hence carried no directional information. 2 5 Results The spectrum of CpCr(CO), at 20 K in the monoclinic crystal of CpMn(CO), was that of a two-site species, each site consisting of a single line with weaker satellites due to the low abundance of ',Cr and 13C isotopes.For certain orientations of the crystal, notably the ac plane, the spectrum of the two sites coalesced to a single signal. In this plane, therefore, the magnitude and sign of the off-diagonal element of the g 2 tensor were directly determinable. This behaviour was entirely normal for a defect paramagnet in a monochic crystal. In the case of CpCr(CO),L, where L is P(C6H5)3, in the triclinic crystal of its Mn analogue an unusual phenomenon was observed. Even in crystals containing as little as 0.3% of the impurity molecule, there appeared to be three locations for the impurity in the lattice. Each 'location' was a doublet due to 31P hyperfine structure, and each one behaved exactly as would be expected for a defect in a triclinic unit cell. There was no site splitting, because in a triclinic unit cell there are no symmetry elements which (in a cell of higher symmetry) connect the different sites.The principal values of the g-tensors of the two species CpCr(CO), and CPC~(CO)~L in their respective Mn-containing matrices are shown in table 1. These are the square roots of the principal values of the g 2 tensors; their direction cosines referred to the crystallographic axes are also indicated. The 53Cr hyperfine interaction, in units of MHz, for CpCr(CO), is also given, together with principal direction cosines referred to the crystallographic axes. The 13C hyperfine interactions of the carbonyl carbon atoms of CpCr(CO),, and the 31P hyperfine interaction of the phosphorus atom of CPC~(CO)~L were virtually isotropic.Average values in units of MHz are given, without directional information.J. R. Morton et al. 3537 Table 1. Principal values of the g- and A-(hyperfinelMHz) tensors for CpCr( CO), and CpCr(C0)2P(C6H5)3, together with their direction cosines referred to the crystallographic axes ~~ tensor direction cosines 1.9969 g 2.0353 2.1339 3 a53 27 44 25 1.9954 2.0207 2.1131 2.0013 g B 2.0080 2.1 108 2.002 gc 2.016 2.115 a3 1 95 CpCr(CO)3 a b C* (0.468, k0.230, 0.853) (-0.785, k0.551, 0.283) (0.405, k0.802, -0.439) (0.453, k0.059, 0.890) (-0.705, *0.635, 0.317) (0.546, *0.770, -0.329) almost isotropic CpCr(CO)*L a* b* C (-0.647, 0.741, 0.181) (0.697, 0.671, -0.253) (0.308, 0.037, 0.951) (-0.478, 0.843, 0.248) (0.735, 0.538, -0.414) (0.482, 0.016, 0.876) (-0.583, 0.784, 0.214) (0.721, 0.621, -0.308) (0.375, 0.025, 0.927) almost isotropic Table 2.Directions of x, y and z referred to the crystallographic axes of c ~ C r ( C 0 ) ~ and CpCr( CO)2L axis direction cosines ~~~~~ ~ CpCr(CO), a b C* X (-0.776, k0.560, 0.291) Y (0.514, k0.293, 0.806) z -0.366, r0.775, 0.515) CpCr( CO)2L a* b* C X (0.653, -0.702, -0.282) z (0.367, -0.032, 0.930) Y (0.662, 0.7 1 1, -0.237) Discussion Notwithstanding the analogy between the Cp negative ion and three carbonyl ligands, CpCr(CO), has lower symmetry than Cr(C0)6. It is customary to define an axis system xyz, where z passes through the chromium atom and the centre of the Cp ring, x is perpendicular to a plane defined by z and a Cr-C or Cr-P bond and y is perpendicular to x and z. We shall use this axis system for both CpCr(CO), and CpCr(C0)2L.In3538 E.S.R. Of CpCr(C03) and CpCr(CO),P( C ~ H S ) ~ table 2 are shown the direction cosines of the axes x, y and z referred to the crystallo- graphic axis systems. Inspection of table 1 confirms the similarity of the three species, which we call A, B and C, trapped in CpMn(CO),L. All three have one principal g-factor near that of a free spin, a second or intermediate g-factor in the range 2.01-2.02 and a third or maximum g-factor close to 2.1 1. All three spectra also carried ,‘P hyperfine structure in the 90-100 MHz range. The lack of anisotropy in the latter, combined with the overlapping of the three spectra, resulted in there being little information in the 31P hyperfine interaction. In table 1 we can also compare the principal g-factors of A, B and C with those of CpCr(C0)3 in its Mn analogue: 1.997,2.035,2.134.Not surprisingly, they are very similar to those of A, B and C. If we examine the principal directions of g,,, in table 1 we note two things. First, the directions of g,,, of A, B and C are nearly parallel; secondly, all three directions are close to that of z in table 2. This means that for A, B and C, the direction of g,,, is very close (a few degrees of arc) to the direction of Cr-C(av), where C(av) defines the centre of the Cp ring. The same is true of g,,, of CpCr(CO), in its matrix. Thus, in both molecules the Cr-C(av) direction can be regarded as a ‘magnetic axis’ along, or very close to, which the g-factor reaches its maximum value. This is very surprising in the case of CPC~(CO)~L, for the P(C6H5), ligand destroys any semblance of a geometric axis.In the case of CpCr(CO),, the Cp-C(av) direction is a natural axis of magnetization, and one would expect it to coincide with that of a principal g-factor. We now examine the plane perpendicular to the magnetic axis z. In CpCr(CO), it is surprising to find that the g-factor is anisotropic in this plane, for in the free molecule z would be a C3 axis, at the very least. A comparison of the vectors in tables 1 and 2 suggests that gint (2.0353) is parallel, or nearly parallel, to x. An examination of the crystal structure of CpMn(CO), projected along z shows that there are three planes containing z which are almost planes of symmetry; these planes contain C( l), C(2) and C(3), respectively, these being the three carbonyl carbons.As pointed out by the crystallographers,2 the most nearly perfect of these planes is that containing z and C( 1). It is, therefore, somewhat surprising to find that the chromium-containing impurity uses not the plane containing z and C(1), but that containing z and C(2). As regards the molecule CPC~(CO)~L, a natural plane of symmetry containing the z axis has been imposed on the C(av)Cr(CO),P skeleton by the substitution of P(C6H5), for a carbonyl ligand. According to the crystal structure of the Mn anal~gue,~ perpen- dicular to this plane (x) is a vector whose direction cosines are (0.653, -0.702, -0.282). Referring to table 1, it is clear that, for all three ‘conformers’, it is gmin that is almost parallel to x.This is in distinct contrast to CpCr(C0)3, where gint was perpendicular to the symmetry plane. The reason for this rather subtle distinction between the two molecules must be sought in the ordering of the energy levels which emerge from the triply degenerate f 2 g level as the symmetry is lowered from o h , through C3u, to C,. The title molecules are Cr d S species containing one electron fewer than required to attain the stable 18-electron configuration. In Oh symmetry, their electronic configuration would be t:,e;. Lowering the symmetry to C,, either as a result of the Jahn-Teller effect, or because of an imposed plane in the case of CpCr(CO,)L, or simply due to the lack of symmetry in the crystallographic site, results in the five-level manifold illustrated in fig.1. The three components of the erstwhile t2g level, t,bO, t,bl and q ! ~ ~ are predominantly (80%) x2-y2, xy and z2, respectively. The components of the eg level, (CI3 and @4, are predominantly yz and xz’. when the magnetic field is parallel to z6 Since the g-shift for Ho parallel to z was large and positive for both molecules, the separation between @o and t,hl must be fairly small, as expected (a crude calculation indicates ca. 3000 cm-’). As regards the plane perpendicular to z, the experimental evidence indicates that x is the direction of gint for CPC~(CO)~, but of gmin for CpCr(CO),L. We can only conclude from this evidence that t,bo contains the unpaired The spin-orbit interaction 2, connects @o andJ. R. Morton et al.3539 Fig. 1. Energy-level schemes for CpCr(C0)3 and CpCr(C0)2P(C6HS)3 in C, symmetry. Arrows at the sides of the figure join levels connected by the spin-orbit interaction, when Ho is parallel to the direction indicated. The symbol ( y z ) is an abbreviation for the atomic orbital Cr 3 4 , , etc. spin in the former and in the latter case, as indicated in fig. 1. The arrows on either side of this figure indicate the levels connected by the spin-orbit interaction for Ifo parallel to the three principal directions. Because of the inversion of +o and +,, x is seen to be the direction of intermediate g in the case of CrCp(CO),, but minimum g in the case of C~CP(CO)~L. The 53Cr hyperfine interaction was measured for CpCr(CO),. As will be seen from table 1, it is highly anisotropic, but its principal values 3,27 and 44 MHz have directions which are (within experimental error) parallel to y, x and z, respectively.In fig. 1 the wavefunctions describing the five d orbitals of an octahedral Cr(C0)6 molecule are given using the xyz axis system defined earlier.' The 53Cr hyperfine anisotropy for an unpaired electron in +o was estimated by combining, in the ratio 2: 1, the anisotropies of x2 - y 2 and y z orbitals7 and adding an isotropic or Fermi-contact term. The results were as follows: axx = aiso ayy = aiso + (2/7) P azz = aiso - (2/7) P where P = yeyn(rP3) for a 3d orbital of chromium. Since the magnetic moment of 53Cr is negative, P will be negative, ca. -100 MHz. With positive aiso due to polarisation effects, a, is expected to be the smallest and azz the largest of the three principal hyperfine values, as observed.Using the experimental values of ayy and azz, one can calculate aiso and P to be 23 and -72 MHz, respectively. With the observed value of axx of 27 MHz, very close to aiso, the validity of the above three equations is confirmed. Even closer agreement can be obtained by incorporating the effects of spin-orbit interaction into the above equations. If y,yn( rP3) is estimated from Hartree-Fock-Slater wavefunctions (-103 MHz),' the experimental value of P indicates an overall chromium 3d spin population of ca. 0.7. We comment finally on the spectrum of CpCr( CO), in solution.* A signal at g = 2.025 in benzonitrile as solvent has been reported and assigned to CpCr(CO),. The above discussion of the energy levels of this molecule implies that in the free state or in solution its electronic configuration would be .. . a:e3 in C3" symmetry. This is the configuration of a Jahn-Teller molecule, and one which we would not expect to be detectable in solution. Moreover, the reported g-factor does not agree with our (g)-value, obtained for CpCr(CO), in its Mn analogue (2.055). Molecules in which a CO ligand has been3540 E.S.R. of CpCr(C0,) and CpCr(CO),P( C,H,), replaced by, say, P(C6H5), have C, symmetry even in solution. Since the C, point-group has no degenerate representations, such species should be detectable in solution. We therefore suspect that the signal attributed to CpCr(CO), in solution is, instead, that of CpCr( CO),L, where L is solvent-derived. We have been informed that experimental confirmation of this hypothesis exists’ and that L is C,H,NC. References 1 T. A. Albright, J. K. Burdett and M. H. Whangbo, Orbital Interactions in Chemistry ( Wiley-Interscience, 2 A. F. Berndt and R. E. Marsh, Acta Crystallogr., 1963, 16, 118. 3 N. Cooley, K. A. Watson, S. Fortier and M. C. Baird, Organometallics, 1986, 5, 2563. 4 J. S. Rollett, Computing Methods in Crystallography (Pergamon Press, London, 1965), chap. 3. 5 J. R. Morton and K. F. Preston, J. Magn. Reson., 1983, 52, 457. 6 A. J. Stone, Roc. R. SOC. London, Ser. A, 1963, 271, 424. 7 J. R. Morton and K. F. Preston, J. Magn. Reson., 1978, 30, 577. 8 T. Madach and H. Vahrenkamp, 2. Naturforsch., Ted. B, 1978, 33, 1301. 9 S. J. McLain, P. J. Krusic, R. D. Farlee and J. Nicholson, unpublished data. New York, 1985), chap. 20. Paper 71661; Received 13th April, 1987

ISSN:0300-9599    

DOI:10.1039/F19878303535

出版商:RSC    

年代:1987

数据来源: RSC