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The α→γ→α→β transitions of para-dichlorobenzene have been studied by employing infrared and n.q.r. spectroscopy as well as differential scanning calorimetry. The γ phase is associated with considerably higher values of some of the intramolecular vibration frequencies. The α→γ transition shows athermal nucleation behaviour as in martensitic transitions. Intermolecular vibration bands around 46 and 85 cm–1 present in γ and α phases disappear in the β phase. The α→β transition seems to be associated with some orientational disorder.
Ultraviolet absorption spectra of acetone and acetone-d 6 have been photographed under fairly high resolution and vibrational analyses carried out. The results indicate that the C(CO)C skeleton of the excited state of acetone is non-planar; CNDO/2 calculations also substantiate this observation.
No abstract is provided for this article.
No abstract is provided for this article.
Infrared spectra of various types of organosulphur compounds have been examined and group frequencies arising from G—S, S—S, N—S, O—S, and C=S stretching vibrations have been assigned and discussed. The C—S bands of thioketals and S—S bands of tri- and tetra-sulphides show splittings due to vibrational coupling. The O—S and N—S stretching frequencies are found around 890 and 820 cm −1 respectively, values which are much higher than the C—S stretching frequencies. Potassium alkyl xanthates exhibit the asymmetric and symmetric stretching frequencies of the CS 2 − ion. The splitting of C—O and C=S stretching bands in dialkyl dixanthogens have been interpreted in terms of the Fermi interaction with the combination tone of C—S and S—S stretching vibrations and with the overtone of S—S stretching vibrations respectively. The relative intensity of the C=S stretching bands in a few derivatives show marked dependence on the electronegativities of the elements directly linked to the thiocarbonyl group. It is found that the earlier assignments of the "[Formula: see text] bands" due to mixed vibrations in thioamide type derivatives have been found to be well justified on the basis of the recent normal coordinate treatment. Another band tentatively designated as the "[Formula: see text] IV band" has been assigned for these derivatives in the region 850–680 cm −1 . Examination of the spectra of a number of thioamide type derivatives has shown no evidence for the presence of thiol tautomers. All of them exist as thiones exhibiting characteristic N—H absorption and "[Formula: see text] bands".
No abstract is provided for this article.
Solid state chemistry deals with a variety of solids, inorganic as well as organic; the solids can be crystalline or noncrystalline. A sound knowledge of the structure of solids as well as of the nature of bonding is essential for an appreciation of solid state chemistry since properties of solids are, by and large, determined by the structure. Crystal chemistry of inorganic solids has been reviewed widely in the literature (see, for example, Adams, 1974; Rao, 1974; Wells, 1984), but there has been effort of late to explore new ways of looking at inorganic structures and to understand their stabilities. In this chapter, we shall briefly review the highlights of inorganic crystal chemistry after summarizing some of the basic information related to crystals and the different types of bonding found in them. We shall also discuss polytypism, organic crystal structures and related topics before finally presenting the models employed to understand the structures of noncrystalline or amorphous solids.
Salient structural features of the important families of cuprate superconductors are briefly reviewed. Correlations between the superconducting transition temperature and some of the crucial structure parameters are discussed. Correlations include those with the in-plane Cu-O distances, apical Cu-O distance, Madelung potentials and bond valence sums. The transformation of $YBa_2Cu_3O_{6.7}$ (123 cuprate) to a $YBa_2Cu_4O_8$ (124)-type phase is examined. Structural features of the newly discovered oxyanion derivatives of cuprates are pointed out
Two-dimensional nanostructures in the form of ultra-thin crystalline films of CdSe and CuSe have been prepared at the organic-aqueous interface by reacting toluene solutions of metal cupferronates with an aqueous solution of N,N-dimethyl selenourea. The films have been examined using electron microscopy and optical spectroscopy. At lower concentrations of the reacting species, the CdSe films formed at the toluene-water interface at approximately 30 degrees C consisted mostly of nanocrystals. With increase in concentration as well as temperature, the interface reaction yielded thicker films which are mostly single-crystalline. We have studied the time-dependent growth of the CdSe film at the interface using UV-visible absorption spectroscopy. Ultra-thin films of CuSe formed at the toluene-water interface are generally single-crystalline.
It is shown that $YBa_2Cu_3O_{7.\\delta}$ $(T_c \\sim 90 K)$ is stable and monophasic over the \\delta=0.0-0.2 range; and \\delta=0.25 to 0.5 compositions are monophasic with well-ordered oxygen-deficient structures. The \\delta=0.3-0.4 compositions $(T_c \\sim 60 K)$ seem to be metastable, undergoing transformations on annealing at 470 K for several hours. The 124 and 247 cuprates of a few rare earths have been prepared and characterized by the ceramic method. These cuprates form intergrowths with each other or with the 123 cuprate. Such epitaxial relations may be of significance in using them in materials applications. $Bi_2Ca_{1-x}Ln_xSr_2Cu_2O_{8+\\delta}$ (Ln=Y or rare earth) shows a maximum in the hole concentration as well as Tc around x=0.25. Thallium cuprates of the type $TlSr_{n+1-x}Ln_xCu_nO_{2n+3}$ and $Tl_{1-x}Pb_xSr_{n+1}Cu_nO_{2n+3}$ not containing Ca and Ba have been prepared and characterized for the first time.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
