Vol 64, No 1 (2019)

Solid solution Zn_2−2xCu_2xSiO₄ with the willemite structure has been synthesized by the proposed solid-phase synthesis procedure. It is shown that the maximum annealing temperature is 1030 ± 1°C because of the decomposition of CuO. The extent of the Zn_2−2xCu_2xSiO₄ solid solution is 7.5 at % Cu. The unit cell crystal-chemical parameters and coefficients of thermal linear and volume expansion are independent of the Cu²⁺ concentration. Melting points of Zn_2−2xCu_2xSiO₄ samples in the homogeneity region are also independent of the dopant index x and close to the values found for undoped Zn₂SiO₄ (1512 ± 1°C). The deformation phase transition in Zn₂SiO₄ and Zn_2−2xCu_2xSiO₄ is found for the first time being 10 ± 2°C below the melting point. The combination of the obtained crystal-chemical and thermal data allowed us to carry out the triangulation of the diagram of the ZnO−SiO₂−CuO system to divide it into five secondary triangles by two-phase equilibria lines.

Anhydrous basic bismuth nitrate Bi₆(NO₃)₂O₇(OH)₂ was shown to be produced by reacting bismuth nitrate with aqueous ammonia under microwave-assisted hydrothermal treatment as a result of hydrolysis. The composition of the basic nitrate was verified by titration, CHNS analyses, DTG, and IR spectroscopy. Photocatalytic tests showed that Bi₆(NO₃)₂O₇(OH)₂ has a photocatalytic activity, but its properties are interior to those of α-Bi₂O₃.

2-Aminopyridine (2-ampy) and acetylacetone has been allowed to react with the Ni(II) and Co(II) metal salts to give complexes of the type [Co^III(acac)₂(2-ampy)₂]ClO₄ (1), [Ni^II(acac)₂(2-ampy)H₂O]ClO₄(2-ampyH) (2), and [Ni^II(acac)₂(2-ampy)H₂O] (3). The crystal structures of the complexes have been determined by X-ray diffraction. The data of antimicrobial analysis have indicated that the complexes have rather good activities against bacterial species. Through investigating the antioxidant activity by FRAP and anti-hemolytic assay, all the metal complexes have shown an acceptable activity. In addition, NiO nanoparticles have been prepared by the combustion synthesis method of complex 3 at 700°C for 8 h.

The structural features of 12 chelate complexes with the general formula [MoO₂(L^m)], where L^m is a tetradentate chelate (N, N, O, O) ligand representing a Schiff base, a salicylaldehyde derivative (m = 1−11), have been considered. In all 12 complexes, the molybdenum atom has a cis,cis,cis-octahedral coordination. Both pairs of N(L^m), O(L^m) atoms occupy both trans- and cis-positions to oxo ligands.

New Pt(IV) perfluorocarboxylate complexes of the composition [Pt(R_FCOO)₄]_n and M₂[Pt(R_FCOO)₆] (R_F = CF₃, C₂F₅; M = Li, Na, K, Rb, Cs, NMe₄) have been synthesized and studied. These complexes are strong oxidizing agents capable of oxidizing alkanes in trifluoroacetic acid under mild conditions to form trifluoroacetic acid esters and acting as catalysts for the oxidative trifluoroacetoxylation of alkanes, cycloalkanes, and framework compounds. They can also be used as starting compounds for the synthesis of other perfluorocarboxylate complexes of platinum in various oxidation states. The structure of (NMe₄)₂[Pt(CF₃COO)₆] · 6CF₃COOH has been determined by X-ray diffraction.

Tri-para-tolylantimony bis(3-nitrobenzoate) (I), tri-para-tolylantimony bis(3,5-dinitrobenzoate) (II), and tri-para-tolylantimony bis(bromoacetate) (III), in which the Sb atoms have a trigonal bipyramidal coordination according to X-ray diffraction analysis, have been synthesized by the reaction of tri-para-tolylantimony (4-MeC₆H₄)₃Sb with 3-nitrobenzoic, 3,5-dinitrobenzoic, and bromoacetic acids in the presence of tert-butyl hydroperoxide. The OSbO axial angles are 171.83(12)°, 173.06(9)°, and 173.82(10)°. The Sb-O and Sb-C bond lengths are 2.109(3), 2.123(3), and 2.095(4)–2.111(5) Å in I, 2.108(2), 2.133(3), and 2.095(4)–2.103(3) Å in II, 2.126(3), 2.133(3), and 2.102(3)–2.115(3) Å in III. The Sb⋯O intramolecular distances (3.105(5), 3.168(5) in I, 3.060(4), 3.096(4) in II, 3.069(4), 3.100(4) ⋯ in III) are ∼0.5 ⋯ smaller than the sum of the antimony and oxygen van der Waals radii.

A design scheme of nanosized sensors based on BC₃ boron-carbon nanotubes (BCNTs) surface-modified by a carboxy group (surface-carboxylated nanotubes) is considered. The potential usefulness of sur-face-carboxylated nanotubes for detecting alkali metals is analyzed. Interactions of a carboxy group with the nanotube surface and subsequent interactions of the thus-prepared nanosystem with lithium, potassium, and sodium atoms are modeled. Calculations are performed using the molecular cluster model in the frame of the density functional theory (DFT) method. Surface-carboxylated boron-carbon nanotubes are proven to highly sensitive to the chosen atoms.

In this research, the formation of Hf_m-Ti_n nanocluster in six configurations of Hf_m-Ti_n and physicochemical behavior of CO₂ adsorption on Hf_m-Ti_n nanoclusters have been studied. The formation of the Hf-CO₂ and Ti-CO₂ bonds has been calculated using the DFT method. The effects of CO₂ adsorption on structural variations and electronic properties have been studied. The adsorption energy ΔE_ads, energy gap (E_g), HOMO and LUMO energies, and dipole moments have been calculated at the 6-311++G** basis set, considering the constant bond lengths of the adsorbed CO₂ molecules on Hf_n-Ti_5-n. The geometrical optimization has been performed by the B3PW91 method. The obtained results of adsorption values allow us to suggest that Hf doping on Ti nanocluster can noticeably improve the adsorption properties of all nanocluster models. Therefore, the decrease in global hardness and energy gaps after CO₂ adsorption on Hf_m-Ti_n nanoclusters can be attributed to the increase of chemical reactivity and hence leads to the lower stability of systems.

The effect of spin—orbit coupling on the electron levels of (5, 3), (8, 7), (11, 3), (18, 11), (10, 5), (8, 8), and (13, 0) gold nanotubes of various diameters and chirality was studied in the framework of the relativistic version of the linear augmented cylindrical wave method. Spin-dependent band structures and electron state densities were calculated. Spin—orbit coupling is manifested as splitting of nonrelativistic dispersion curves. For the dispersion curve that crosses the Fermi level in the (5, 3) tube of the minimum radius, this splitting reaches 0.5 eV and decreases on going to low-lying valence band states. An increase in the radius and a decrease in the cylindrical surface curvature of these nanotubes suppress the spin—orbit splitting. All tubes possess a metal type band structure in which the number of conduction channels increases with increasing radius of the nanotube.

The energies of mixing (interaction parameters) and temperature ranges of stability of solid solutions Lu_{1 − x}Ln_xVO₄ (where Ln is a rare-earth element (REE), scandium, or yttrium) with the zircon structure were calculated using the crystal-energy theory of isomorphous miscibility. It was shown that, with increasing atomic number of REE in the Ce—Lu series, the calculated energies of mixing and critical decomposition temperatures of the solid solutions regularly decrease. The substitution limits at various temperatures, the thermodynamic phase stability, and the temperature of transition to a metastable state were determined. The thermodynamic stability diagram of the REE vanadate solid solutions Lu_{1 − x}Ln_xVO₄ was presented. The results of the work can be used for searching the compositions of matrices and activators of new laser and other materials.

It was determined that the SrS—In₂S₃ system is of the eutectic type with the incongruently melting compound SrIn₂S₄ and limited regions of solid solutions based on polymorphic modifications of In₂S₃. The compound SrIn₂S₄ crystallizes in the orthorhombic system (space group Fddd) with the unit cell parameters a = 2.090 nm, b = 2.113 nm, and c = 1.302 nm. The incongruent melting point of SrIn₂S₄ is 1220 K, and its microhardness is H = 2650 MPa. The composition and melting point of the eutectic are 73 mol % In₂S₃ and 1170 K, respectively. The solubility of SrS in α-In₂S₃ at 1070 K reaches 6 mol % SrS.

Nanosized cadmium sulfide particles (quantum dots; QDs) were synthesized in ethylacetate and (poly)methylmethacrylate by the reaction between cadmium trifluoroacetate and H₂S formed by the hydrolysis of thioacetamide (TAA). The stability of colloid solutions was provided by thioacetamide complexes on the surface of CdS particles. The Cd(II): TAA ratios and the constants of the reaction between cadmium trifluoroacetate and thioacetamide in the (CF₃COO)₂Cd · nH₂O-TAA-P system, where TAA was thioacetamide and P was ethylacetate or (poly)methylmethacrylate, were determined by spectrometric methods. The size of CdS particles and the rate of their formation were estimated. The data on the effect of synthesis conditions on the spectral luminescent properties of CdS in a (poly)methylmethacrylate matrix were presented.