摘要:

One bond and long range JCH coupling constants for a series of 2-quinolone derivatives are described. The spectra of the parent compound shows considerable second order character at both 15 MHz and 90 MHz in CDCl3and in DMSO-d6solution, which has been discussed. The variations in the coupling patterns resulting from the fusion of the lactam ring and change of heteroatom are highlighted.

ISSN:0038-7010    

DOI:10.1080/00387019408002504

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The 200 MHz1H NMR spectra of the anticonvulsant, methetoin,1, have been studied in CDCI3solution at ambient temperatures in the presence of the achiral lanthanide shift reagent tris(6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium(III),2, and the chiral reagent, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato] europium(III),3., With added 1, appreciable enantiomeric shift differences, ΔΔδ, can be induced for the aryl protons and both methyl groups of1. In particular, using3:1molar ratios from ca. 1.2–2, with 0.046 molar1, signals from theCH3CH2and the phenylorthoprotons for the enantiomers of 1 are well resolved, exhibiting excellent potential for direct determinations of enantiomeric excess of1. Relative magnitudes of lanthanide-induced shifts for the different nuclei of 1 with added2or3are compared and discussed.

ISSN:0038-7010    

DOI:10.1080/00387019408002505

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The new vector model (NVM),1designed for approaching the intensity of the secondary transition of the substituted benzene chromophore (towards 260 nm), has been based on MNDO calculations and on the SKLAR's vector model.2–9It leads to the simple relationship: εsm,c= 4905 (TS + V). Experimental intensity is given as εsm, the maximum of the smoothed absorption curve, as it has been defined by BALLESTER and RIERA10(the calculated value is: εsm,c). The vibrational component of intensity (V) is based, too, on their work. S is an increasing function of the number of substituents and of their ability to capture photons. It can be related to the UV cross section of the molecule, increasing when the UV cross section increases. T is the modulus of a vector related to the electronic transition moment. It is based on the distorsion of the π electronic charges, from a pure D6hsymmetry scheme. The MNDO method is used to calculate these charges. Thus, the modulus of the electronic transition moment being related to: μ = (TS)1/2, is the result of two complementary approaches.

ISSN:0038-7010    

DOI:10.1080/00387019408002506

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Electron paramagnetic resonance (EPR) spectra of Cu2+doped lithium potassium sulphate (LP3) have been studied at different temperatures. The spin-Hamiltonian g and A parameters have been evaluated. Phase transitions in LP3 were observed at low temperature. The measured g-values indicate a rhombic field for Cu2+in the lattice at the temperature range 300–215 K. Between 215 K and 123 K an orthorhombic field suggested. The bonding parameter (∞2), Fermi-contact term (K) and the free ion dipolar term (P) are evaluated using the principal g and A values. The ground state were runction for Cu2+ion in (LPS) is determined.

ISSN:0038-7010    

DOI:10.1080/00387019408002507

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Electron energy loss spectra under scattering of electrons on 4-amino-N-(n-butylphenylene)-1, 8-naphthalimide and 4-methylamino-N-(o-tolyl)-1, 8-naphthalimide in a vapour phase is studied. The primary electron energy was varied from 6 to 60 eV and the scattering angle was 90°. It is found that the differential cross section of excitation of complex organic molecules into some triplet states can reach the same value as singlet ones.

ISSN:0038-7010    

DOI:10.1080/00387019408002508

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The use of stable free radicals such as aminoxyl spin-labels has been recently exploited for obtaining information on solution structures of peptides (1,2) and proteins (3,4) from multidimensional NMR spectra. In those reports, it has been suggested that an efficient spin-labelling of water and dimethylsulphoxide (DMSO) solvents may be achieved and the paramagnetic solvent yields relaxation effects on backbone proton nuclei which are directly driven by the molecular surface accessibility. Upon the addition of the paramagnetic probe, the observation of absence in chemical shifts changes and of nuclear relaxation effects which are fully rationalised in terms of the solution structure, support a dynamic model for the interaction between the chemical probe and the biomolecule where weak collisional adducts favour the dipolar coupling of the unpaired electron with the outer nuclei of the investigated molecule.

ISSN:0038-7010    

DOI:10.1080/00387019408002509

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The concentration dependence of surface enhanced Raman scattering (SERS) of adsorbed 4-aminophenyl disulfide on surfaces of silver and gold has been investigated. It has been found that the spectral qualities are inversely proportional to the concentration of solutions applied. Excellent SERS spectral enhancement and perpendicular orientation could be achieved for the sample applied from 4 × 10−6Msolution rather than that from 0.001Msolution. This phenomenon was termed as “dilution effect” on SEES spectrum.

ISSN:0038-7010    

DOI:10.1080/00387019408002510

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The new complexes trans-[PdX2(H4MTO)2] (X = Cl, Br, I),trans-[PdX2(H3MMTO)2] (X = Cl, Br, I),trans-[PdX2(SH3)2] (X = Cl, Br), [Pd(H4MTO)4]CI2and [Pd(H3MMTO)4]CI2, where H4MTO = monothiooxamide, H3MMTO = N(o)-methylmonothiooxamide and SH3= N(s)-methylmonothiooxamide, have been prepared. The complexes were characterized by elemental analyses, conductivity measurements, X-ray powder patterns, thermal methods and spectroscopic (UV/VIS, FT-IR, Laser-Raman) studies. The vibrational analysis of the complexes is given using NH/ND and CH3/CD3isotopic substitutions. Monomeric square planar structures are assigned for the complexes in the solid state. The neutral monothiooxamides behave as monodentate ligands coordinating through their thioamide sulfur atom. The complex [Pd(SH2)2] was isolated during the thermal decomposition oftrans-[PdCl2(SH3)2].

ISSN:0038-7010    

DOI:10.1080/00387019408002511

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The new complexes CuX2(LH2), CuX2(SH3) (X = Cl, Br), CuX(LH2), CuX(SH3) (X = Cl, Br, I), CuX(H4MTO)2(X = Cl, Br), Cul(H4MTO) and CuX(H3MMTO)2(X = Cl, Br, I), where LH2= N.N′-dimethyl-monothiooxamide, SH3= N(s)-methylmonothiooxamide, H4MTO = monothiooxamide and H3MMTO = N(o)-methylmonothiooxamide, have been prepared. The complexes were characterized by elemental analyses, conductivity measurements, magnetic moments and spectroscopic (UV/VIS, FT-IR, Laser-Raman) studies. The vibrational analysis of the complexes has been given using NH/ND, CH3/CD3and63cu/65cu isotopic substitutions. The neutral monothiooxamides behave as monodentate ligands in the Cu(I) complexes coordinating through their thioamide sulfur atom. The ligands LH2 and SH3act as bidentate chelating agents in the Cu(II) complexes with ligated atoms being the thioamide sulfur and the amide oxygen.

ISSN:0038-7010    

DOI:10.1080/00387019408002512

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A facile oxygen-induced chemisorptive replacement reaction occurs when a Bi(0001)-O overlayer is exposed to hydrogen chloride at 298K. The overlayer, which conforms to the stoichiometry BiOCl2, is stable in contrast to analogous chemistry observed earlier with a Pb(110) surface. Evidence for discrete localized states associated with Bi2+or Bi3+species is observed from shifts in the Bi(4f) binding energies while the charge distribution within the bismuth-chlorine bond is shown to be sensitive to the presence of oxygen adatoms within the oxy-chloride overlayer.

ISSN:0038-7010    

DOI:10.1080/00387019408002513

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor