Structural features of SnCl<Subscript>4</Subscript>–<Emphasis Type="Italic">ortho</Emphasis>-dimethoxybenzene complexes as derived from ab initio computations

Computations for the possible structures of SnCl₄–ortho-dimethoxybenzene complexes and initial components have been performed by MP2/LANL2DZ method. Computation results have been compared with experimental data of ³⁵Cl nuclear quadrupole resonance. cis-Octahedral structure of the complex through the coordination of both oxygen atoms has been confirmed. This complex differs considerably from the majority of studied tetrachlorostannane complexes of cis-octahedral structure in terms of the ratios of axial and equatorial Sn–Cl bond distances, p _σ electron density, and ³⁵Cl NQR frequencies for axial and equatorial chlorine atoms.     

Adsorption and catalytic properties of sulfated aluminum oxide modified with cobalt ions

The adsorption properties of sulfated aluminum oxide (9% SO ₄ ^2- /γ-Al₂O₃) and a cobalt-containing composite (0.5%Сo/SO ₄ ^2- /γ-Al₂O₃) based on it are studied via dynamic sorption. The adsorption isotherms of such test adsorbates as n-hydrocarbons (C₆–C₈), benzene, ethylbenzene, chloroform, and diethyl ether are measured, and their isosteric heats of adsorption are calculated. It is shown that the surface sulfation of aluminum oxide substantially improves its electron-accepting properties, and so the catalytic activity of SO ₄ ^2- /γ-Al₂O₃ in the liquid-phase alkylation of benzene with octene-1 at temperatures of 25–120°C is one order of magnitude higher than for the initial aluminum oxide. It is established that additional modification of sulfated aluminum oxide with cobalt ions increases the activity of this catalyst by 2–4 times. It is shown that adsorption sites capable of strong specific adsorption with both donating (aromatics, diethyl ether chemosorption) and accepting molecules (chloroform) form on the surface of sulfated γ-Al₂O₃ promoted by cobalt salt.     

Thermochemistry of С<Subscript>60</Subscript> fullerene solutions in benzene,toluene, <Emphasis Type="Italic">о</Emphasis>-xylene,and <Emphasis Type="Italic">о</Emphasis>-dichlorobenzene at 298.15 K

The enthalpies of dissolution of С₆₀ in benzene, toluene, о-xylene and о-dichlorobenzene are measured in a sealed high-sensitivity calorimeter at 298.15 K and at different concentrations of the solute. The standard enthalpies of dissolution of С₆₀ in these solvents are determined.     

Theoretical and experimental study of the transformation of 2-pyridone-5-amide into nitrile

Molecular and crystal structures of 2,4-dimethyl-6-oxo-1,6-dihydropyridine-3-carboxamide (1), 2,4-dimethyl-6-oxo-1,6-dihydropyridine-3-carbonitrile (2), and 2-chloro-4,6-dimethylniсotinonitrile (3), which are the products of sequential transformations, are studied by means of single crystal diffraction. The procedure for synthesizing each compound is described. All of the compounds are characterized using IR and ¹H NMR spectra. Possible reaction pathways are simulated using the density functional theory (DFT).     

Structure of a bimolecular crystal of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane and methoxy-<Emphasis Type="Italic">NNO</Emphasis>-azoxymethane

The crystal structure of the bimolecular crystal of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and methoxy-NNO-azoxymethane (МАМ) (1:2) is studied. The CL-20 molecules adopt a ζ-conformation. The crystal structure is formed by layers of CL-20 and МАМ molecules, between which there are shortened NO^δ–?N^δ+O contacts of the neighboring CL-20 and МАМ molecules.     

Palladium-containing composite nanomaterials based on polycaprolactam: Formation and structure

Novel Pd(0) nanocomposites using polycaprolactam as a reducing and stabilizing matrix are synthesized. Data on the nanoparticle formation mechanism in a polycaprolactam matrix under the conditions of changing pH of the medium and reagent concentration ratios are obtained. The nanocomposite structure is studied by electron and infrared spectroscopy, X-ray diffraction analysis, atomic force and transmission electron microscopy. The size of metal-containing particles in the composite composition and their size distribution are determined. The obtained nanocomposites can serve as heterogeneous catalysts.     

Simulation of glycyrrhizic acid associates with cholesterol in methanol

There are experimental evidences that in the methanol solution of glycyrrhizic acid (GA) and cholesterol, the cholesterol molecules have two different types of the environment. One corresponds to free molecules and another corresponds to the molecules associated with GA. However, the nature of these associates remains unclear. The all-atom molecular dynamics simulation of GA solutions in methanol is performed. It is shown that, contrary to aqueous solutions, GA in methanol does not form small stable clusters, even in the presence of cholesterol. The arising associates do not have distinct structures and exist for no longer than dozens of nanoseconds. The concentrations of these clusters and their stability constants are estimated. It is necessary to assume the existence of larger-scale associates to explain the experimental data.     

Possibilities of powder X-ray diffraction methods in determining structural characteristics of carbon materials

The possibilities of using powder X-ray diffraction methods in the study of carbon materials are discussed. To determine the phase composition of the crystalline materials the X-ray phase analysis is employed; the real structure is established by the harmonic analysis of diffraction profiles; the structural features and phase composition of the nanomaterials are found by the radial electron density distribution function.     

X-ray photoelectron and X-ray emission study of the electronic structure of hexanuclear Mn(II,III) pivalate complexes

The electronic structure of hexanuclear Mn(II,III) pivalate complexes with tetrahydrofuran and isonicotinamide are studied by X-ray photoelectron spectroscopy and X-ray emission spectroscopy. It is shown that when isonicotinamide substitutes for tetrahydrofuran the spin state of manganese ions is retained; the electron density increases on the manganese and oxygen atoms of the [Mn₆(O)₂Piv₁₀] core.