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The near-ultraviolet absorption spectra of polyphenyl derivatives of the IVb and Vb elements have been studied in detail. In the case of the triphenyl derivatives of the Vb elements, the unshared p-electrons on the central atoms interact strongly with the π-orbitals of the benzene rings. When the central atoms do not possess unshared electrons as in the case of the derivatives of the IVb and the pentavalent Vb elements, there appears to be no such resonance interaction. The Hammett reactivity constants of the para- and meta-trityl, triphenylsilyl, and triphenylgermanyl groups are estimated to be close to zero. However, the reactivity constant of the triphenylsilyl group in the para position of phenol is estimated to be about 0.30. The infrared spectra of the phenyl derivatives of the IVb and Vb elements show smooth trends due to mass effects of the central atoms, in the C=C skeletal, C—H out-of-plane, and other vibrations. The absorption frequencies which are assigned to the phosphorus-phenyl and silicon–phenyl bonds in the literature do not appear to be unique for these linkages.
Adsorption of CO has been investigated on the surfaces of polycrystalline transition metals as well as alloys by employing electron energy loss spectroscopy (eels) and ultraviolet photoelectron spectroscopy (ups). CO adsorbs on polycrystalline transition metal surfaces with a multiplicity of sites, each being associated with a characteristic CO stretching frequency; the relative intensities vary with temperature as well as coverage. Whilst at low temperatures (80–120 K), low coordination sites are stabilized, the higher coordination sites are stabilized at higher temperatures (270–300 K). Adsorption on surfaces of polycrystalline alloys gives characteristic stretching frequencies due to the constituent metal sites. Alloying, however, causes a shift in the stretching frequencies, indicating the effect of the band structure on the nature of adsorption. The up spectra provide confirmatory evidence for the existence of separate metal sites in the alloys as well as for the high-temperature and low-temperature phases of adsorbed CO.
Abstract : This infrared bibliography is based on a systematic search of the literature on infrared spectroscopy up to the end of 1960. The literature search has been made by going through journals as well as through Chemical Abstracts. As a general rule, any paper of interest in the field of infrared spectroscopy is included. Examples of fringe areas include microwave spectra where rotational constants are given, papers on preparation of chemical compounds where infrared spectra are used for identification, papers on Beer's law, references to mathematical treatments such as group theory and statistical mechanics and so on. The bibliography has been divided into four sections: I, Organic compounds; II, Inorganic Compounds (a, of non-metals; b, of metals); III, Polymeric Compounds; and IV, Minerals and Ores.
Charge-ordered rare earth manganites Nd 0.5 Ca 0.5 MnO 3 , La 0.25 Nd 0.25 Ca 0.5 MnO 3 , Pr 0.7 Ca 0.3 MnO 3 and Pr 0.6 Ca 0.4 MnO 3 are found to exhibit dielectric constant anomalies around the charge-ordering or the magnetic transition temperatures.Magnetic fields have a marked effect on the dielectric properties, indicating the presence of coupling between the magnetic and electrical order parameters.The observation of magnetoferroelectricity in these manganites is in accord with the recent theoretical predictions of Khomskii and coworkers.
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Thermogravimetry and Cu K-absorption edge measurements show that the superconducting YBa2Cu3O7 sample (annealed in O2) contains more oxygen than the nonsuperconducting sample annealed in N2, the former has a less distorted structure with the actual composition not far from the ideal one. Oxides of the formula Y1−xBa2Cu3O7 (x = 0.05, 0.10 and 0.15) annealed in oxygen also possess the perovskite structure and show high-Tc superconductivity. The superconduccting transition temperature seems to generally increase with the nominal Cu 3+ Cu 2+ ratio in the superconducting copper oxides. Control of the Cu 3+ Cu 2+ ratio (and hence the density of states at the metal-nonmetal transition in the non-superconducting state) through the oxygen stoichiometry or an appropriate cation substitution seems to provide a basis for synthesizing high-Tc copper oxides.
Reaction of a mixture of neodymium carbonate, HCl, oxamic acid and glutaric acid under hydrothermal conditions gives rise to a new mixed carboxylate of neodymium, [Nd4(H2O)2(OOC(CH2)3COO)4(C2O4)2], I. The structure, determined using single crystal X-ray diffraction, comprises a helical column formed by the grafting of the oxalate unit on to helical NdO9 chains, cross-linked by the glutarate anions. It is noteworthy that the pitch of the helix is equivalent to the length of the oxalate unit. Furthermore, I shows about 1.1 times the SHG activity of urea.
Detailed calculations on the condensed phases of biphenyl have been carried out by the variable shape isothermal-isobaric ensemble Monte Carlo method. The study employs the Williams and the Kitaigorodskii intermolecular potentials with several intramolecular potentials available from the literature. Thermodynamic and structural properties including the dihedral angle distributions for the solid phase at 300 K and 110 K are reported, in addition to those in the liquid phase. In order to get the correct structure it is necessary to carry out calculations in the isothermal-isobaric ensemble. Overall, the Williams model for the intermolecular potential and Williams and Haigh model for the intramolecular potential yield the most satisfactory results. In contrast to the results reported recently by Baranyai and Welberry, the dihedral angle distribution in the solid state is monomodal or weakly bimodal. There are interesting correlations between the molecular planarity, the density and the intermolecular interaction.
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