Journal of Structural Chemistry最新文献

Expressions are derived for the relationship between the metallicity index _m with the ratio of the absolute value of the potential electron energy density (V) to the kinetic energy density (G) at the bond critical point (BCP) using the quantum theory of atoms in molecules (QTAIM) and the electron localization function (ELF) value at the BCP. It is found that the ELF maximum (ELF^BCP = 1) is achieved at (xi _{m}^{text{BCP}}=-4). It is shown that calculated (xi _{m}^{text{BCP}}) values should not exist in a range (-4<xi _{m}^{text{BCP}}<-1). The (xi _{m}^{text{BCP}}) values are calculated and analyzed for some simple molecules and crystals.

Amorphous transparent SiC_x:H and SiC_xN_y:H films are prepared at a temperature of 200 °C and a discharge power of 200 W in an inductively coupled RF plasma reactor using hexamethyldisilane vapors and additional argon and/or nitrogen gases. The influence of N₂ flow rate on the morphology, chemical structure, elemental composition, transmittance, refractive index, contact angle, and film deposition rate is studied. Plasma components are determined by optical emission spectroscopy. It is shown by HRTEM and EDS mapping methods that the annealed Cu/SiC_x:H/Si(100) sample has distinct substrate/film and film/copper layer interfaces, no Cu diffusion occurs, and that the SiC_x:H the film can be considered as a promising diffusion barrier layer. Stability of the films during storage under ambient conditions is studied. The tendency of SiC_xN_y:H films to oxidize is revealed by EDS, IR spectroscopy, and XPS.

The In₂O₃–Ga₂O₃–ZnO ternary oxide is prospective for electronics applications. Promising methods of fabricating In₂O₃–Ga₂O₃–ZnO based transistors require a technique for the preparation of X-ray pure powders. Data on the influence of the studied organic complexing agent on the morphology of obtained powders are reported. It is shown that ethylene glycol is more preferable to use than citric acid since the powders prepared in the first case contain no admixture phases.

Single crystals of two new compounds, (L-CysH⋯L-Cys)(HC₂O₄) (I) and (L-CysH⋯L-Cys⋯L-CysH)(HC₂O₄)₂·0.5H₂O (II), were obtained. Crystal structures were solved and refined using single-crystal X-ray diffraction, and compared with the previously known orthorhombic and monoclinic modifications of the simple salt (L-CysH)(HC₂O₄). Compound I crystallizes in the triclinic crystal system (space group P1, Z = 2) and contains (L-CysH⋯L-Cys) dimeric cations with very short O⋯O interatomic distance of 2.434(2) Å. Hydrogen oxalate anions form head-to-tail type chains with very short hydrogen bonds, characterized by O⋯O distances of 2.422(2) Å and 2.417(3) Å. The crystal lattice of II is monoclinic with the space group C2, Z = 4. It contains a new type of cation, that has never been observed before for cysteine salts, i.e. trimeric (L-CysH⋯L-Cys⋯L-CysH) cation. Protonated L-cysteinium cations are connected to the zwitterionic L-cysteine moiety through the same oxygen atom of the carboxylate group via hydrogen bonds, with O···O distances of 2.6410(18) Å and 2.4888(19) Å. Similar to the structure I, the hydrogen oxalate anions form head-to-tail type chains linked by short hydrogen bonds with O⋯O distances of 2.4369(17) Å and 2.4330(17) Å, respectively. The crystals were characterized by IR and Raman spectroscopy. The batches obtained on crystallization were also characterized by X-ray powder diffraction, in order to check the phase purity of all the sample.

We present the results of studying HfO_x films formed from tetrakis(dimethylamino)hafnium with different times of water supply pulses. The stoichiometry of the samples obtained is estimated by spectral ellipsometry and Auger electron spectroscopy. It is shown that an increase in the water supply duration promotes an increase in the x value in the HfO_x layer. When the time of water supply pulses varies from 10 ms to 1000 ms, x values ranging from 1.76 to 1.84 are obtained. A method based on the refractive index is proposed to estimate the stoichiometry of HfO_x layers.

Samarium hydrogen iodate Sm(IO₃)₃·HIO₃ was successfully synthesized by the unconventional low-temperature solution-melt method, its structure was determined by X-ray diffraction analysis of single crystals. This compound crystallizes in the monoclinic space group P2₁/c with lattice parameters: a = 10.4637(6) Å, b = 7.4629(5) Å, c = 14.0174(13) Å, β = 110.53(0), Z = 6. In the studied structure, samarium atoms are surrounded by 8 oxygen atoms in a polyhedron in the form of a distorted square antiprism. The iodate groups are linked through common oxygen atoms of the SmO₈ antiprism into a three-dimensional framework. The compound was characterized by X-ray diffraction, IR and NQR spectroscopy and EDX analysis.

An aroylhydrazone compound N’-(5-chloro-2-hydroxybenzylidene)-3-methylbenzohydrazide (H₂L) has been synthesized and characterized by elemental analysis, infrared and electronic spectra, and ¹H NMR spectrum. With the aroylhydrazone and maltol (HL^a) or ethyl maltol (HL^b) as ligands, two oxidovanadium(V) complexes, [VOLL^a] (1) and [VOLL^b] (2), have been synthesized and characterized by elemental analysis, infrared and electronic spectra, and ¹H NMR spectra. Structures of the complexes were further confirmed by single crystal X-ray determination. The V atoms in the complexes are coordinated by the ONO donor atoms of the aroylhydrazone ligand L, OO donor atoms of maltolate (L^a) or ethyl maltolate (L^b) ligand, and one oxido O atom, forming octahedral coordination. The complexes function as effective olefin epoxidation catalysts with hydrogen peroxide as terminal oxidant and sodium hydrogen carbonate as a co-catalyst.

7-Bromo-5-(tert-butyl)-2-phenyl-1H-indene (1) and 6,7-dibromo-2,4-dimethyl-2,3-dihydro-1H-inden-1-one (2) are analyzed by single crystal X-ray diffraction. The conformational structure, vibrational spectrum of molecules, topology and hierarchical complexity of crystal structures are discussed. The structure of 1 is layered and contains (100) molecular layers of the tts topological type. The structure of 2 does not contain long molecular ensembles but demonstrates short Br⋯O contacts linking molecules into a centrosymmetric dimer.

The first aqueous silver borate nitrate Ag₃B₄O₆(OH)₂(NO₃) has a non-centrosymmetric crystal structure (P4₃2₁2, a = 10.0196(3) Å, c = 9.2594(2) Å). The compound is prepared by soft hydrothermal synthesis inside an evacuated quartz ampoule. The structure of the resulting 1D–5B-borate compound is formed by [B₄O₆(OH)₂]^2– chains consisting of two triborate rings with a common (2Δ3□:(‹Δ2□›–‹Δ2□›–)^∞ tetrahedron and NO₃ triangles with silver atoms between the rings. The relationship between the structures of Ag₃B₄O₆(OH)₂(NO₃), Tl₂B₄O₆(OH)₂·2H₂O and the kernite Na₂B₄O₆(OH)₂·3H₂O (also formed by [B₄O₆ (OH)₂]^2– chains) is discussed.

The study of manganese-substituted barium hexaferrite BaFe_12–xMn_xO₁₉ with a degree of substitution x from 0 to 2 is presented. The samples are prepared by the solid-phase synthesis at a temperature of 1275 °C and isothermal holding for 5 h. The elemental composition of the samples is determined using energy dispersive spectroscopy, which shows good correspondence with the specified calculated compositions. Monophasicity of all synthesized samples is confirmed by powder X-ray diffraction. In addition, the effect of manganese substitution on the unit cell parameters is estimated. In the differential scanning calorimetry study of the properties, the effect of manganese substitution for iron on the Curie points of the samples obtained, which are caused by changes in the magnetic structures of the produced materials, is determined. The results indicate a significant effect of manganese substitution on the properties of barium hexaferrite and confirm the possibility to control the substitution process for the production of materials with adjustable magnetic characteristics.