摘要:

The n.q.r. spectra of a number of complexes of the type [Y3PCo(CO)3]2have been recorded. The results are compared with those from related studies.

ISSN:0008-4042    

DOI:10.1139/v74-552

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Length change and sorption isotherms have been determined for water, ammonia, ethyl chloride, and methane on compacted samples of zeolite NaX. Methane sorption at 0 °C and ethyl chloride sorption at −10°C were accompanied by little or no framework distortion as monitored by length change measurements; sorption of ammonia in the temperature range −50 to −70 °C produced more appreciable distortion; and water sorption at room temperature caused large changes. In each case the framework distortion was correlated with different stages in the sorption process. The sorption isotherms for the ammonia/NaX system indicated the possibility at high uptakes of two-dimensional condensation or multilayer formation. The critical temperature for two-dimensional condensation would be −70 °C.

ISSN:0008-4042    

DOI:10.1139/v74-553

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The isothermal delayed fluorescence along with the visible (6000 Å) photostimulated fluorescence and phosphorescence emissions have been recorded and analyzed in the following systems: diphénylamine (DPA) – ether rigid glass and carbazole (C) – ether rigid glass at 77°K. The electron–cation recombination after visible light stimulation has been analyzed in terms of a kinetic model already described (10). The triplet quantum yields of the DPA and C molecules are calculated and compared to the existing experimental values. The rate constant ratio (β) of populating the first triplet (T1) relative to populating the first excited singlet (S1) after the recombination event has taken place, is equal to about 2 in both systems investigated here. A value of 4.4 was obtained for indole and tryptophan in the same matrix. This difference can only be explained in terms of various singlet state energies for these molecules and also in terms of the stimulating energies used in these experiments.

ISSN:0008-4042    

DOI:10.1139/v74-554

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The Schiff base, bis(trifluoroacetylacetone)triethylenetetraamine (H2L), forms a nickel complex with the composition NiC16F6H22N4O2(NiL). Crystals of NiL belong to the monoclinic space groupP21/cwitha = 10.040(2),b = 15.077(7),c = 13.943(7) Å, β = 111.88(5)°,Dc = 1.610 g/cc,Do = 1.61(2) g/cc, Z = 4. A total of 1686 independent reflections withF2 ≥ 2σ(F2), 2θ ≤ 42° were measured on a Picker 4-circle diffractometer by the θ–2θ scan technique with MoKα radiation. A full matrix least squares refinement of the structure yielded an unweightedRfactor of 0.057. The structure confirms that condensation of triethylenetetraamine with trifluoroacetylacetone occurs through the acetyl group, not through the trifluoroacetyl group. The nickel atom is octahedrally coordinated by the four nitrogen and two oxygen atoms of the L2−ligand. The triethylenetetraamine moiety has the α-configuration, so that the oxygen atoms occupycispositions on the octahedron. Distortions in the octahedral geometry are due to the three contiguous five-membered rings in the complex; the average N—Ni—N angle is 81.1°. The trifluoroacetylacetone fragments are essentially planar, with an average O—Ni—N angle of 90.6°. These rings are folded about the O—N lines, the folding angles being 17.1 and 8.0° for the two rings. The average Ni—O, Ni—N (trigonal), and Ni—N (tetrahedral) distances are 2.037, 2.044, and 2.128 Å, respectively.

ISSN:0008-4042    

DOI:10.1139/v74-555

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

A device has been set up to determine quantitatively the weak fluorescence intensities of pigment molecules. It consists of a laser spectrofluorimeter. The excitation beam can be produced with either a He/Cd laser (441.6 nm) or a He/Ne laser (632.8 nm). This system allows us to detect the fluorescence of dilute chlorophyllaorbsolutions of the order of 10−12 mol/l. This sensitivity also permits the study of the emission spectra from chlorophyll in monomolecular or solid states, and since a polarization rotator has been incorporated into our apparatus, one may presume some possible orientation of the molecules.

ISSN:0008-4042    

DOI:10.1139/v74-556

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Various transition metal chelates were found to quench1O2in the liquid phase.1O2was generated either photochemically, from an ozonide, or with a microwave source and reacted with rubrene or 3-methyl-2-pentene. Rate constants for1O2quenching by the chelates were measured in various solvents using the three1O2sources, and compared with the constants of previously known1O2quenchers. The most efficient chelates quenched1O2at close to the diffusion controlled rate, as did β-carotene. Some quenchers of1O2in the liquid phase were qualitatively shown to quench in the solid state. The possible1O2quenching mechanisms of the chelates are discussed.

ISSN:0008-4042    

DOI:10.1139/v74-557

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The densities and volumetric specific heats of the alkaline earth chlorides have been measured in water at 25 °C in the concentration range 0.01 to 0.4 Mwith a flow densimeter and a flow microcalorimeter. Apparent molal volumes and heat capacities have been derived.

ISSN:0008-4042    

DOI:10.1139/v74-558

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The crystalline conformation of polypivalolactone was determined by analysis of the chain conformational energies and it was found that the minimum energy corresponds to a planartransconformation for the ester group. The result was compared to published X-ray data based on fiber diffraction which show a significant deviation fromtransplanarity. This difference is discussed in terms of the relative energies involved and by comparison with literature crystallographic results of low molecular weight carboxylic esters. It is stressed that because of the paucity of information in fiber diffraction, internal energy considerations are important for assigning internal rotation angles. Crystallographic results for low molecular weight compounds show that deviations greater than 10° fromtransplanarity are rare for ester groups.

ISSN:0008-4042    

DOI:10.1139/v74-559

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The catalytic effectiveness of eleven aromatic hydrocarbon donors in the acetolysis of 2,4,7-trinitro-9-fluorenylp-toluenesulfonate (TNF-OTs) has been examined. For nine of these donors, the kinetic data were analyzed to obtain the rate constant,kc, for acetolysis of the 1:1 donor–substrate complex, and the 1:1 donor–substrate association constant,K. Two measures of catalytic effectiveness, logkcand logkcKcorrelate well with the highest occupied molecular orbital energy of the donor,E(HOMO), calculated by the Hückel molecular orbital (HMO) method. The success of these correlations is considered to mean that the transition state for acetolysis resembles a π-complex. A model based on Mulliken's charge-transfer theory in its simplest form leads to an estimate of 0.11 of an electron transferred from the donor to the acceptor substrate in the complexed transition state.

ISSN:0008-4042    

DOI:10.1139/v74-560

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The use of RhH(DBP)3as a very active homogeneous hydrogenation catalyst is described and the equilibrium constant for its dissociation to the catalytically active RhH(DBP)2evaluated.

ISSN:0008-4042    

DOI:10.1139/v74-561

出版商:NRC Research Press    

年代:1974

数据来源: NRC