摘要:

AbstractSyntheses of stable and metastable isomers for each of the chlorophenylphosphoranes, PhPCl4, Ph2PCl3and Ph3PCl2, together with some Lewis acid salts are described. Comparison of Raman spectra of the salts with one set of isomers suggests an ionic formulation [PhnPCl 4 −n+] [Cl−] (1 ≤n≤ 3); correlation with spectra of Sb and As analogues of known structure suggest pseudo‐trigonal bipyramidal (Ψtbp) structures for the other isomers. Thermodynamically stable isomers are ionic Ph3PCl+Cl−, Ψtbp Ph2PCl3and Ψtbp PhPCl4. Vibrational Raman assignments for the skeletal modes are given for each of the isomers and some of their Lewis acid salts. Frequency shifts arising from non‐bonded interactions in the ionic species are compared with those in the methyl‐s

ISSN:0377-0486    

DOI:10.1002/jrs.1250260202

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman spectra of 14 positional isomers of carboxylic acids esters with 17 skeletal atoms, CH3(CH2)m−1COO(CH2)n−1CH3(CmCOOCn) withm+n= 15 andm= 1—14, have been measured in the crystalline state at liquid nitrogen temperature. The relationship between the observed wavenumbers of the characteristic bands and the positions of the —C(=O)—O— group in the molecular chain was examined. All of the positional isomers of CmCOOCnwithm+n= 15 exhibit a strong LAM‐1 band in the region between 147 and 136 cm−1. The LAM‐1 wavenumbers for the isomers which have the —C(=O)—O— group almost in the middle of the molecular chain are slightly higher (147—143 cm−1) than those for the isomers which have the same group almost at the end of the chain. In order to elucidate the observed LAM‐1 wavenumbers, the Raman spectra of two homologous series of esters, C5COOCnand C6COOCn, were examined. All isomers of CmCOOCngive a strong band at about 1135 cm−1assignable to thek= 1 mode of the C—C stretching vibrations. Some of the isomers give an additionalk= 1 band at about 1125 cm−1. The isomers of CmCOOCn, which exhibit the twok= 1 bands, have the —C(=O)—O— group almost in the middle of the molecular chain, and appear to give the LAM‐1 band at the higher wavenumbers. In the crystalline state all of the esters examined take the all‐transconformati

ISSN:0377-0486    

DOI:10.1002/jrs.1250260203

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA vibrational study of then‐butanoate ion in aqueous solution was undertaken. Four isotopic species (d0, 2‐d2, 3‐d2and 4‐d3) of the potassiumn‐butanoate were studied. A normal coordinate analysis was carried out, using the force fields established for the propanoate ion and forn‐butane, according to the moiety of then‐butanoate ion being considered. The Raman spectra of aqueous solutions (2.5 M) and of the solid phases are described. A spectral subtraction method, which is discussed, was used in order to assign the observed bands, on the basis of their behaviour with temperature increase, to thetransand thegaucheconformers. Finally, an assignment is proposed, taking into account all the experimental observations, for the four isotopic species, except in the δ(CH),v(CD) a

ISSN:0377-0486    

DOI:10.1002/jrs.1250260204

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman and infrared spectra of diglycolic acid and its potassium salts in aqueous solution were recorded from 4000 to 200 cm−1. Vibrational assignments were made for all the observed wavenumbers on the basis of isotopic wavenumber shift, depolarization ratios and group wavenumber considerations and comparison with accepted assignments for certain vibrational modes in other similar compounds. The three compounds (the acid, the acid salt and the neutral salt) belong to theCssymmetry group, but their conformations are quite different. In the crystalline state, the acid salt has a strong hydrogen bond and appeared to be of type A according to Speakmann's classificatio

ISSN:0377-0486    

DOI:10.1002/jrs.1250260205

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe vibrational contribution to the internal rotation potential of toluene and nitromethane is calculated for different force fields which were constructed using permutation‐inversion group and dependent on the internal rotation angle. The assignments of Raman spectra were made using experimental data obtained for the liquid and vapour (toluene) states and supported by vibrational analysis calculation. The vibrational contribution calculated with a ρ‐independent force field represents the kinetic energy contribution to the internal rotation potential of the molecule in question. For toluene (C6H5CH3) and nitromethane (CH3NO2) the kinetic energy contribution is zero, and for C6D5CHD2and CHD2NO2it has a cos (2ρ) dependence. This sort of calculation may serve as a check of any force field used for assigning molecular vibrations by comparing calculated internal rotation potentials in excited vibrational states with the parameters of the potential found from the fit of vapour band con

ISSN:0377-0486    

DOI:10.1002/jrs.1250260206

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSERS spectra of cytosine, 1‐methylcytosine, 5‐methylcytosine and 1,5‐dimethylcytosine on a gold colloid are reported. A tentative assignment of Raman bands is made by comparison with the normal Raman spectra in aqueous solution. This analysis reveals a preferred non‐planar orientation of cytosine and 1‐methylcytosine and a more planar orientation of 5‐methylcytosine and 1,5‐dimethylcytosine with respect to the metal surface, the C=O group being determinant in the interaction. A comparative study using the result obtained previously using silver and copper colloids as supports shows important differences in the electrodynamic behaviour of these molecules which depend on the presence of the methyl substituents and the nature of the metal on whic

ISSN:0377-0486    

DOI:10.1002/jrs.1250260207

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractUrea inclusion compounds containingn‐alkane (CnH2n+2withn= 8 and 19) guest molecules were investigated by means of Raman spectroscopy. Vibrational modes due to the urea confirm the structural identify of the inclusion compounds, and lattice modes of the urea host structure were assigned tentatively. Investigations of the vibrational properties of the CnH2n+2guest molecules were focused on the longitudinal accordion mode (LAM‐1) and the methyl rocking r(CH3) vibrations. These modes were studied as a function of (i) the length (n) of the guest molecule, (ii) temperature and (iii) pressure. The vibrational bands characteristic of the end‐gauche gt‐ andtg‐defects were therefore identified. From these results, trends in the relative amounts ofgauche gt‐ end‐groups for the various guest molecules were assessed in both the low‐ and high‐temperature structural phases of the compounds and found to be constant and of the order ofca.5%. It was also shown that the amount ofn‐alkane chains distorted at their ends depends markedly on the hydrostatic pressure. These results are discussed and compared w

ISSN:0377-0486    

DOI:10.1002/jrs.1250260208

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractRaman scattering was used to probe electronic properties in In‐based structures. First, Raman signatures of undoped and doped InAlAs and InGaAs bulk materials and Raman spectra of InAlAs—InGaAs heterostructures were recorded. Raman scattering by coupled longitudinal optic phonons and two‐dimensional electron gas provides a powerful probe of electronic properties in this structure. More precisely, Raman results allowed information to be obtained on the two‐dimensional gas electron carrier concentration. Then, a specific advantage of the micro‐Raman method was demonstrated by the observation of the carrier concentration the vicinity of the gate of an operating high electronic mobility transistor (HEMT). Qualitative variations of carrier concentration in the two‐dimensional electron gas were observed and compared successfully with carrier concentration calculations using Monte Carlo

ISSN:0377-0486    

DOI:10.1002/jrs.1250260209

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe resonance Raman spectrum of bis(isomaleonitriledithiolato)nickelate(II) was investigated in order to assess the extent of the electronic delocalization within the chromophore. Previous results for the isomeric species bis(maleonitriledithiolato)nickelate(II) indicated an extensive delocalization involving the Ni—S, C=C and C≡N bonds. The present results conclusively indicate that in the case of [Ni(imnt)]2−the delocalization is much more restricted, which is in line with a previous suggestion concerning the marked difference in the two species concerning the stability towards oxidation. The resonance Raman results show a very pronounced enhancement of thev(Ni—S) and δ(ring) modes via the Albrech'sAterm, which is supported by the simulations undertaken using the transform method and the time‐dependen

ISSN:0377-0486    

DOI:10.1002/jrs.1250260210

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250260201

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY