Publications

Preparation, characterization and properties of C-60 And C-70 - spectroscopy, structure, anions, interaction with electron-donors and superconductivity

Preparation and characterization of the fullerenes, C60 and C70, are described in detail, including the design of the generators fabricated locally. The characterization techniques employed are UV-visible, IR, Raman and C-13 NMR spectroscopies, scanning as well as transmission electron microscopy and mass spectrometry. The electron energy level diagram of C60 as well as the one-electron reductions of C60 and C70 leading to various anions are discussed. Electronic absorption spectra of C60- and C60(2-) are reported. Phase transitions from the plastic to the crystalline states of C60 and C70 are examined. Based on a C-13 NMR study in a mixture of nematic liquid crystals, it has been demonstrated that C60 retains its extraordinary symmetry in solution phase as well. Interaction of C60 and C70 with strong electron-donor molecules has been investigated employing cyclic voltammetry. Superconductivity of K(x)C60 has been studied by non-resonant microwave absorption; Na(x)C60 as well as K(c)C70 are shown to be non-superconducting. Doping C60 with iodine does not make it superconducting. Interaction of C60 with SbCl5 and liquid Br2 gives rise to halogenated products.

ChemInform Abstract: EXAFS of Catalytic Materials

No abstract is provided for this article.

Electrical properties of inorganic nanowire–polymer composites

Composites of nanowires of ZnO, RuO2 and Ag with polyaniline (PANI) as well as polypyrrole (PPy) have been prepared, for the first time, by an in-situ process, in order to investigate their electrical properties. Characterization by electron microscopy and IR spectroscopy indicates that there is considerable interaction between the oxide nanowires and the polymer. The room-temperature resistivity of the composites prepared in-situ varies in the 0.01–400 Ω cm range depending on the composition. While the resistivities of the PANI–ZnONW and PPy–ZnONW composites prepared by the in-situ process are generally higher than that of PANI/PPy, those of PANI–RuO2NW and PANI–AgNW are lower. Composites of ZnONW with polyaniline prepared by an ex-situ process exhibit a resistivity close to that of polyaniline.

Pm3m-Fm3m transformations of alkali halides and the Born-Mayer model. CsCl and its solid solutions with RbCl, KCl and CsBr

Some energy aspects of the Pm3m—Fm3m transformation of CsCl have been studied quantitatively. Effects of addition of RbCl, KCl and CsBr to CsCl on the transformation have been examined. Above a critical concentration of RbCl or KCl, the transformation becomes irreversible and at much higher concentrations the Fm3m form gets stabilized. Lattice energy differences between the Pm3m and Fm3m forms of CsCl as well as its solid solutions have been calculated employing various forms of the modified Born-Mayer model with three, and four, structure-dependent parameters. Both the three and the four parameter equations are satisfactory when a higher van der Waals term is used. The four parameter equation satisfactorily explains the variation in the transformation energy of the solid solutions of CsCl with the mole fraction of RbCl.

Substituent and solvent effects on the n → π* (′U ← ′A) transition in aliphatic carbonyl derivatives: evidence for hyperconjugation in the excited states of molecules

No abstract is provided for this article.

Chemistry of materials

Electronic transitions of hydrogen bonded complexes: an electron energy loss spectroscopic study

Electronic spectra of hydrogen bonded complexes have been studied by electron energy loss spectroscopy and assignments made based on experimental orbital energies from HeI photoelectron spectra and molecular orbital calculations. Electronic transitions of diethyl ether-HCl and SO2·HCl complexes show small shifts from those of HCl and the free electron donor, as expected of weakly interacting systems. Electronic spectra of the dimers of formic and acetic acids are markedly different from those of the monomers. Dimers show characteristic n→π* and π→π* transitions in the 7–11 eV region.

Non-bonded interactions in cyclobutane-thiones

Using UVPES and electronic spectral data the presence of an interaction between thd 1,3-thiocarbonyl groups in 2 has been identified. EHT calculations also predict such an interaction. Presence of weak interaction between 1,3-carbonyl and thiocarbonyl groups in 3 has been inferred from electronic absorption and emission spectra.

A layered chlorophosphate, Na3[Cd4Cl3(HPO4)2(H2PO4)4], containing Na+ ions in the interlamellar space

Reaction between CdCl2·H2O and NaH2PO4·H2O under hydrothermal conditions gives rise to a new cadmium chlorophosphate of the formula Na3[Cd4Cl3(HPO4)2(H2PO4)4], I. This material crystallizes in the orthorhombic system with space group Fmm2 (no. 42). I has macroanionic layers of [Cd4Cl3(HPO4)2(H2PO4)4]3− with Na+ ions in the interlamellar space. The discovery of such compounds suggests that metathetic reactions carried out under hydrothermal conditions may provide a novel route for the synthesis of new open-framework structures.

Proton exchange and hydrogen bonding in hydroxylamine derivatives

Proton exchange in hydroxylamines, RNHOH, has been investigated by nuclear magnetic resonance spectroscopy. Hydrogen bonding of the hydroxylamines and their N,N-and N,O-disubstituted derivatives by self-association as well as by their interaction with electron donors has been studied by nuclear magnetic resonance and infrared spectroscopy. The results indicate that the OH group participates to a greater extent in hydrogen bonding than the NH group. The O-H⋯Y (Y = donor site) hydrogen bonds are found to be generally stronger than the N-H⋯Y bonds.

Large magnetoelectric effect in the Al1-xGaxFeO3 family of multiferroic Oxides

AlFeO3, GaFeO3 and Al0.5Ga0.5FeO3, all crystallizing in a non-centrosymmetric space group, are multiferroic and also exhibit magnetoelectric properties, with Al0.5Ga0.5FeO3 showing unusually large magnetocapacitance at 300 K.

A study of micropores in single-walled carbon nanotubes by the adsorption of gases and vapors

No abstract is provided for this article.

Chapter 7. Physical chemistry of solids

C. N. R. Rao, K. J. Rao, S. Ramasesha, D. D. Sarma and S. Yashonath, Annu. Rep. Prog. Chem., Sect. C: Phys. Chem., 1992, 89, 179 DOI: 10.1039/PC9928900179

Magnetic excitations in charge-ordered Nd _0.5 Ca _0.5 MnO ₃ : A Brillouin scattering study

Brillouin scattering studies on single crystals of a charge-ordered manganite, Nd0.5Ca0.5MnO3, have been carried out for the first time. The spectra show two modes at (B-mode) and 60 GHz (S-mode). The B-mode frequency and intensity from 300 K to 27 K, covering both the charge ordering transition at 250 K and the antiferromagnetic transition, at 170 K, exactly follow the same temperature dependence as the d.c. magnetic susceptibility. The B-mode is associated with bulk magnetic excitations and the S-mode with surface magnetic excitations of the manganite with ferromagnetic correlations. The study is strongly indicative of the presence of ferromagnetic inhomogeneities in the charge-ordered as well as antiferromagnetic phases.

Phase transformations of rare earth sesquioxides La2O3, Nd2O3, Pr2O3 and Y2O3

The C form of La2O3 has been prepared and its transformation to the A form is found to take place at ∼590°C. The C→A transformation of Nd2O3 takes place at 550°C. The temperatures as well as the energies of activation of the phase transformations of the rare earth sesquioxides vary with the size of the cation. Y2O3 undergoes a reversible phase transformation in the temperature range 400–900°C. The phase transformation of La2O3, Nd2O3 and Pr2O3 have been followed by electrical conductivity measurements. Presence of water vapour lowers the activation energy for the conduction process as well as the temperature of transformation.

Single-walled nanotubes by the pyrolysis of acetylene-organometallic mixtures

Gas-phase pyrolysis of acetylene along with a metallocene or with a binary mixture of metallocenes in flowing Ar or Ar + H2 at 1100°C yields single-walled carbon nanotubes. Pyrolysis of Fe(CO)5-acetylene mixtures in Ar at 1100°C also gives single-walled nanotubes. The diameter of the nanotubes is generally around 1 nm, showing thereby that on pyrolysis under the dilute conditions employed, the organometallic precursors give rise to very fine metal particles essential for the formation of such nanotubes.

⁵⁷<font>Fe</font> Mössbauer and Mo K-EXAFS Investigations of <font>Mo</font>_x<font>Fe</font>_3−x<font>O</font>₄, an Interesting Mixed-Valent Oxide System

Interaction of nitrogen and oxygen with C60

V. Vijayakrishnan, A. K. Santra, T. Pradeep, R. Seshadri, R. Nagarajan and C. N. R. Rao, J. Chem. Soc., Chem. Commun., 1992, 198 DOI: 10.1039/C39920000198