摘要:

AbstractPolarized Raman spectra of oriented single crystals of (CH3CH2NH3)2SnCl6measured over the temperature range 15–300 K have been used to investigate the mechanism of the structural transition at 125 K. A detailed study of some of the external modes and of the internal modes of both the SnCl62−and CH3CH2NH3+ions in the high‐ and low‐temperature phases has enabled the structure of the disordered high‐temperature phase to be confirmed and suggestions for the structure of the low‐temperature phase to

ISSN:0377-0486    

DOI:10.1002/jrs.1250160402

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe infrared and Raman spectra of 5‐methyl‐2‐thiocytosine and its oxygen analogue in the solid state were recorded in the range 4000–200 cm−1. Normal coordinate calculations were performed for these compounds using a simple Urey‐Bradley force field for the in‐plane vibrations and a valence force field for the out‐of‐plane vibrations of the planar skeleton. The assignments of the vibrational fundamentals were made on the basis of normal coordinate calculations and the frequency shifts of bands onN‐deuteriation, The assignments are discussed in relation to vibrational assignments of som

ISSN:0377-0486    

DOI:10.1002/jrs.1250160403

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractUsing excitation radiation of wavelength 248 nm, the peptide linkages of poly(L‐lysine) give rise to important pre‐resonance enhancements in the Raman spectra of the amide bands, specially of the amide II band located in the 1550–1570 cm−1shift region. Using the same excitation wavelength, aromatic amino acids and histidine exhibit resonance enhancement, and their resonance Raman spectra are easily obtainable without a fluorescence background contribution. This background is very large, particularly in the case of phenylalanine when longer wavelength excitation is used. The Raman spectra of native and thermally denatured ribonuclease A have been investigated using 248 nm excitation radiation. These spectra show the major contribution of the tyrosine residues of the protein. It seems that the behaviour of the tyrosine doublet is not a completely adequate probe for following the unfolding of the

ISSN:0377-0486    

DOI:10.1002/jrs.1250160404

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe infrared and Raman spectra of liquid and the infrared spectrum of solid CCl3SBr have been obtained. It was observed that CCl3SBr reacts both with infrared windows made of CsI and with powdered KI, producing CSCl2, and that it also reacts with AgCl windows giving CCl3SCl as a gaseous product.

ISSN:0377-0486    

DOI:10.1002/jrs.1250160405

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractCompacted discs prepared from a mixture of finely divided particles of a compound diluted in a large excess of metal powder facilitate the measurement of Raman spectra for some compounds which give poor scattering by conventional techniques. The method is most useful with coloured compounds. The advantages include simplicity, increased signal‐to‐noise ratio by factors of up to 1000 and decreased or altered fluorescence. The effect appears to be caused mainly by small crevices in the compacted metal surface which act as internal mirrors to produce many small multiple‐reflection cells, but there is also evidence of an electronic interaction with the metal surface. Silver, aluminium and copper matrices were studied, silver being found to be the most advantageous, although aluminium under certain conditions may also be effe

ISSN:0377-0486    

DOI:10.1002/jrs.1250160406

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractResonance Raman spectra and excitation profiles are reported for six azo dyes in CCl4solutions through the visible absorption spectrum region. The excitation profiles observed for the five most intense fundamentals in each dye indicate interference between two overlapping electronic manifolds.

ISSN:0377-0486    

DOI:10.1002/jrs.1250160407

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractExcitation profiles of fundamentals of 4‐nitro‐4′‐diethylaminoazobenzene and 4‐nitro‐6‐cyano‐4′‐(N‐cyanoethyl‐N‐ethylamino)azobenzene reported in the preceding paper are interpreted quantitatively with multi‐mode, three electronic states calculations of Raman intensities. It is demonstrated that the visible absorption spectrum of these azo dyes consists of two overlapping electronic manifolds of nearly equal intensity but with different geometries. Vibrational displacement parameters are determined for five most active totally symmetric vibrations in each dye. The interpretation is supported by observed overtone and combination band intensities. Evidence is presented indicating that inhomogeneous broadening and pre‐resonance scattering from higher excited states play an important role in shaping excitation profiles in the

ISSN:0377-0486    

DOI:10.1002/jrs.1250160408

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman spectra are reported for several bridged diquaternary salts of 2,2′‐bipyridine. Resonance Raman spectra and some excitation profiles of the coloured radical monocations obtained from the diquaternary salts by one‐electron reduction are also reported. Selected frequencies of the parent dications are correlated with changes in the torsional angle between the aromatic rings of the bipyridinium moiety. These correlations, when applied to the spectra of the radical monocations, suggest that the radicals exhibit reduced torsional angle and increased inter‐ring bond order, compared with the parent dications. These changes are consistent with predictions of increased inter‐ring π‐electron delocalization, associated with radical formation. The torsional angle appears to decrease for the radical monocations with increasing number of bridging methylene groups. This is opposite to the trend known to occur in the pare

ISSN:0377-0486    

DOI:10.1002/jrs.1250160409

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractSystems of copper(I), silver(I) and gold(I) cyanides dissolved in aqueous solutions of sodium thiosulphate in different molar ratios have been studied by Raman Spectroscopy. CuCN dissolves completely in aqueous thiosulphate solution in a 1:3 CuCN to S2O32−ratio, forming only mixed cyanothiosulphate species. No evidence was found for the formation of Cu (CN)2−, Cu(CN)32−or Cu(CN)43−. The mixed cyano copper complex was isolated as a white solid insoluble in water and most other solvents. The solid probably consists of a polymeric structure with bridging cyanide and thiosulphate. AgCN dissolves completely in aqueous thiosulphate solution in a 1:1 AgCN to S2O32−ratio, resulting in the formation of Ag(CN)2−and Ag(S2O3)23−species. As the concentration of thiosulphate increases Ag(CN)2(S2O3)3−and Ag(CN)2(S2O3)25−are formed. There is strong evidence for the existence of bridging silver thiosulphate complex in solutions of low S2O32−concentration. AuCN dissolves completely in aqueous thiosulphate solution in a 1:2 AuCN to S2O32−ratio, forming Au(CN)2−, Au(CN) (S2O3)2−and Au(S2O3)23−. No evidence was found for the formation of species of higher coordination number on increasing the concentration of S2O32−, which indicates that the linear two‐coordinate gol

ISSN:0377-0486    

DOI:10.1002/jrs.1250160410

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRelative intensities of the resonance Raman bands of four azo and two phthalein dyes and two colourless aromatic compounds in the solid state have been evaluated by recording the addition Raman spectra using the divided KBr disc method. The 984 cm−1band of potassium sulphate was used as the intensity standard. From the relationship between the relative intensity and the sample concentration, the scattering coefficients for representative resonance Raman bands and the sum of the absorption coefficients at the wavelengths of the excitation and the Raman lines were estimated simultaneously for each dy

ISSN:0377-0486    

DOI:10.1002/jrs.1250160411

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY