摘要:

AbstractResonance Raman studies of iron protoporphyrin‐IX dimethyl ester chloride [FeIII(PPDME)Cl] in the presence of biologically relevant axial ligands such as 2‐methylimidazole (2‐MeIm) and 1,2‐dimethylimidazole (1,2‐Me2Im) revealed the occurrence of photoreduction even under aerobic conditions by excitation near the Soret absorption band. A comparison of the vibrational modes sensitive to the oxidation, spin and coordination states of the photoreduced and chemically reduced forms of FeIII(PPDME)Cl confirmed that the reduction of the central iron atom in the high‐spin state takes place without any reduction of the porphyrin ring. No photoreduction is observed in pure dichloromethane solvent but trace amounts of alcohols and also some other polar solvents, which facilitate the separation of ion pairs, catalyse the process of photoreduction. From the exponential dependence of the fraction of sample reduced on the rate of photoreduction and illumination time, the rate constant for photoreduction,k−1R= 10 min, is obtained and the action spectrum of photoreduction shows a maximum coinciding with the Soret absorption band. The electron transfer from the axially ligated 2‐MeIm to iron appears to be a primary step in photoreduction. From the dependence of photoreduction on the concentration of 2‐MeIm, the ligand‐free, intermediate spin FeII(PPDME) was identified as the intermediate species formed du

ISSN:0377-0486    

DOI:10.1002/jrs.1250220802

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractTris(dimethylammonium) nonachlorodiantimonate (DMACA) is a ferroelectric with a transition temperatureTc= 242 K. Low‐frequency Raman spectroscopic studies were carried out on this crystal within the temperature range 100‐300 K to look for possible spectral changes resulting from the phase transition. A detailed analysis of frequencies, line widths and intensities was made through the phase transition in order to understand its nature. It follows from the analysis that pseudo‐spin‐phonon interactions of higher order are effective in th

ISSN:0377-0486    

DOI:10.1002/jrs.1250220803

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectra were obtained and analysed for polyhedrin and virion protein ofTrabala vishnounuclear polyhedrosis virus (TvNPV‐P and TvNPV‐VP, respectively). It was found that the secondary structures of the protein of the two samples differ: the protein of TvNPV‐P has predominantly an α‐helical and β‐sheet structure whereas that of TvNPV‐P contains predominantly a β‐sheet content, with an α‐helix content and a lower random‐coil or β‐turn content. All tyrosyl residues in the protein of TvNPV‐P are exposed, whereas 80% of the tyrosyl residues are exposed and 20% are buried in the protein of TvNPV‐VP. The majority of the tryptophan residues in the protein of TvNPV‐VP are in a hydrophobic environment. The TvNPV‐VP has atrans‐gauche‐transconf

ISSN:0377-0486    

DOI:10.1002/jrs.1250220804

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractResonance Raman spectra of two azo dyes, 2‐hydroxy‐2′‐carboxy‐5‐methylazobenzene and 2‐hdroxy‐2′‐carboxy‐5‐methoxyazobenzene, in the solid state and in 0.1MNaOH solution were investigated. For comparison, their infrared absorption spectra were also recorded in the solid state and in solution in chloroform. Characterization of the Bands in the Raman spectra of the alkaline solution and their assignments to different hybridized modes were made on the basis of the deprotonated azo and quinonoid molecular forms (in resonanc

ISSN:0377-0486    

DOI:10.1002/jrs.1250220805

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectroscopy was used to distinguish the individual members of the two feldspar subgroups. All feldspars were found to exhibit a characteristic, intense line between 500 and 515 cm−1which is attributed to a mixed SiOSi (or SiOAl) bending/stretching mode. However, discrimination between the related members within each subgroup relies on the change in frequencies and band widths which occur in the external lattice modes and in the SiO stretching region. Spectra were recorded from single crystals and powders and demonstrate that the laser Raman microprobe can provide non‐destructive and rapid identification of feldspars on the micr

ISSN:0377-0486    

DOI:10.1002/jrs.1250220806

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman and infrared (IR) spectra of diethyl sulfide (CH3CH2SCH2CH3), 2‐chlorodiethyl sulfide (ClCH2CH2SCH2CH3), and 2,2′‐dichlorodiethyl sulfide (mustard gas) (ClCH2CH2SCH2CH2Cl) were measured and their vibrational frequencies were compared to calculated frequencies reported by Sosaet al.the calculated frequencies were used to make probable assignments of the vibrational bands to normal modes of the molecules. Raman depolarization ratios for diethyl sulfide and 2‐chlorodiethyl sulfide also aided in their vibrational assignments. Good agreement of the calculated frequencies with the experimental values was found except for the CS and CCl stretching frequencies, which were consistently calculated to be lower than the experimentally found values. The experimental spectra also provide evidence for the presence of more than one stable molecular conformation in the liquid phase for each of the three sulfides. This has been observed for diethyl sulfide in previ

ISSN:0377-0486    

DOI:10.1002/jrs.1250220807

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe self‐broadening of theQ‐branch vibration‐rotational lines in the CARS spectrum of HCl was studied over the pressure range 0.002‐1.000 bar and the temperature range 298‐1048 K. The broadening coefficients, σp, are dependent onJat 298 and 550 K but are independent ofJat higher temperatures; the σpvalue of 1048 K is only about 25% of its value forJ

ISSN:0377-0486    

DOI:10.1002/jrs.1250220808

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractImperfections in the incident laser beam polarization modulation technique in linear polarization Raman measurements are calculated on the basis of the Stokes‐Mueller formalism. An equation for the depolarization ratio in totally symmetric Raman bands of molecules with cubic point group symmetry is derived, yielding a depolarization ratio of ρ′obs.= 1.38 × 10−3for the ν1CCl stretching vibration in the C35Cl4species. The comparison of the computed depolarization ratio with the smallest experimental value reported so far, ρobs.= 2.30 × 10−3, implies that recent attempts to explain the observation of a non‐zero depolarization ratio for the ν1mode in liquid CCl4by intermolecular interactions present in the condensed phase are less releva

ISSN:0377-0486    

DOI:10.1002/jrs.1250220809

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman (SER) spectra of pyridine and thiophenol on a copper colloid prepared in isopropanol were obtained. Aggregation of the colloid, which occurs only slowly in the presence of adsorbates, was found to be essential to the detection of SER spectral features with excitation at 660 nm. As with aqueous copper sols, thiophenol was found to adsorb more strongly than pyridine to the copper surface. However, both adsorbates required greater concentrations in the bulk solution than for aqueous systems in order for SER features to be observe

ISSN:0377-0486    

DOI:10.1002/jrs.1250220810

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0377-0486    

DOI:10.1002/jrs.1250220801

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY