Vol 64, No 2 (2019)

The results of structural and electrophysical characterization of substituted bismuth niobates Bi₃Nb_{1 – x}Er_xO_{7 – δ} , promising oxygen-ion conductors, are presented. The homogeneity extents were determined and crystallochemical parameters of solid solutions were calculated using X-ray powder diffraction and electron microscopy with energy-dispersive microanalysis (SEM-EDX). The stability of the solid solutions and the occurrence of phase transitions in them were determined by differential scanning calorimetry and dilatometry. The electrical conductivity of sintered samples was studied by impedance spectroscopy.

Hydrolysis of water-ethanol solutions of tetrabutoxytitanium (TBT) in the presence of a chelating agent at various pH values and 100°C yielded nanosized anatase or titanium oxyhydrate. When precipitation occurred at pH of 0.8–8.6, anatase was formed; its crystallite size after calcination at 400°C was 4.8–7.1 nm. Precipitation at pH 10.5–12.7 yielded a poorly crystallized oxyhydrate phase, which converted, after being calcined at 400°C, to a mixture of an oxide phase (unidentifiable by X-rays) and anatase having crystallite sizes of 41–42 nm. Scanning electron microscopy verified the crystallite size determined by X-ray powder diffraction. Benzene adsorption by the prepared oxide materials decayed rapidly from 10 to 0.5 g/100 g adsorbent as pH in the solutions used in the synthesis increased.

Nanosized europium phosphates Eu₃PO₇, Eu(PO₃)₃, and Eu(PO₃)₃: Eu²⁺ have been prepared by low-temperature extraction-pyrolytic method. Optimal temperature and time of precursor pyrolysis for preparing luminophor containing europium in different oxidation states have been determined. Phosphate luminophore based on Eu³⁺ exhibit intense red luminescence with λ_max ∼ 600–650 nm. Luminescence spectra of Eu(PO₃)₃: Eu²⁺ are characterized by emission bands in the region 400–700 nm typical for both Eu³⁺ (the bands of ⁵D₀–⁷F_j(j = 0, 1, 2) transitions), and Eu²⁺ (the band of 4f⁶5d → ⁸S_7/2 transition). Luminescence-exciting wavelengths provide different contribution to the radiation intensity of both Eu²⁺ and Eu³⁺.

The thermal behavior of hydroxylaminate uranyl complexes [UO₂(NH₂O)₂(H₂O)₂] ‧ H₂O, [UO₂(NH₂O)₂], and [UO₂(i-C₃H₇NHO)₂(H₂O)₂] ‧ 2H₂O has been studied. The complexes decompose at a low temperature (<200°C) resulting in nanoscale powders of uranium dioxide. The composition of solid decomposition products for each complex has been determined by powder X-ray diffraction. For the complex with isopropylhydroxylamine, the composition of the gaseous decomposition products has been determined. Schemes of redox reactions, which can take place during the thermal decomposition of the complexes, are proposed. It has been suggested that the redox reactions are dependent on the substituents at the nitrogen atom of the hydroxylaminate ligands.

Triarylbismuth dicarboxylates Ar₃Bi[OC(O)R]₂, Ar = p-Tol, R = CH₂Cl (I); Ar = Ph, R = C₆H₄OMe-2 (II), CH=CHPh (III) have been synthesized by the reactions of tri(para-tolyl)bismuth with monochloroacetic acid and triphenylbismuth with 2-methoxybenzoic and cinnamic acids in methyl-tert-butyl ether in the presence of tert-butyl hydroperoxide with a high yield. The Bi atoms in complexes I–III have a distorted trigonal bipyramidal coordination with carboxylate ligands in axial positions (OBiO angles, 171.06(6)° (I), 170.46(12)° (II), 175.39(8)° (III)). The Sb-O and Sb-C bond lengths are 2.283(2), 2.288(2) Å and 2.185(2)–2.199(2) Å (I), 2.265(7), 2.268(7) Å and 2.194(7)–2.218(8) Å (II), and 2.310(2), 2.310(2) Å and 2.200(2)–2.210(3) Å (III). Molecules of complexes I–III have intramolecular contacts between the Bi atom and the O atoms of carbonyl groups: the Bi⋯O(=C) distances are 2.990(2), 2.985(3) Å (I), 2.753(8), 2.739(8) Å (II), and 2.688(2) Å (III). The structural organization in crystals of complexes I–III is caused by weak inter-molecular hydrogen bonds H⋯O of 2.61–2.65 Å (I), 2.47–2.50 Å (II), and 2.56 Å (III).

New cyclometalated neutral iridium(III) complexes [Ir(L)₂(dbm)] have been synthesized, where L is 2-arylphenanthroimidazoles with various electron-donor or acceptor substituents, dbm is dibenzoyl-methane. The compositions and structures of the ligands and complexes have been studied by X-ray diffraction and high-resolution mass spectrometry. In the absorption spectra of the complexes, a bathochromic shift of the absorption maxima is observed with an increase in the electron donor properties of the ligands. All the complexes show the reversible redox behavior; redox potentials fall in the range of 0.8–1.6 V. The combination of the obtained results allows us to consider the synthesized compounds as potential photosensitizers in solar cells.

Quantum-chemical modeling of anionic forms of malic acid H₂mal and the model complex [V^V(O)₂(mal)]^– in which the mal^2– ligand is coordinated to the metal ion through its carboxyl and hydroxyl oxygen atoms has been performed by the DFT M06/631G(d,p) method. It has been demonstrated that the participation of the hydroxyl group, which loses its proton only in an alkaline medium, in the formation of malate complexes in an acidic medium is not due to its acid dissociation, but to the process of competitive replacement by a more electropositive metal ion. Calculations show that the simultaneous absence of the protons at the carboxyl and hydroxyl groups leads to electron excess in the region of the –CH₂–CHO– bonding. The formation of bonds with electropositive metal ions decreases the electron density in this region, which results in the stabilization of the doubly charged anion.

In this study, quantum chemical calculations using MPW1PW91 method were applied to analyze the solvent effect on the NMR parameters for a platinum-based anticancer drug, namely complex trans-(NHC)PtI₂Py. The solvent effects on isotropic magnetic shielding tensor data (σ_iso) for Pt and C_NHC atoms and spin–spin coupling constants of Pt–C and Pt–N in the complex were studied by the self-consistent reaction field theory (SCRF) based on the Polarizable Continuum Model (PCM). The linear correlations between these parameters and dielectric constants of solvents were studied. The σ_iso (Pt) values in different solvents were correlated with the Kirkwood–Bauer–Magat equation (KBM).

The FeS–PbS system was studied by differential thermal, X-ray powder diffraction, and micro-structural analyses and microhardness measurements. It was determined that the FeS–PbS system is a quasibinary section and is of the eutectic type. The coordinates of the eutectic point are 45 mol % PbS and 1123 K. Narrow solubility regions based on the initial components form.

The phase complex is found and the chemical interaction is studied in the composition polyhedra of a quinary reciprocal system based on halides, metavanadates, and molybdates of lithium and potassium. The compositions of low-melting mixtures were determined for the possible use as electrolytes for chemical power sources and heat-storage materials.

The phases NdF₃ (I), x (II), NdTi₂O_4.75F_0.5(SO₄)_0.5 · 3H₂O (III), NdTiF₃(SO₄)₂ · 6H₂O (NdTiOF(SO₄)₂ · 6H₂O) (IV), Nd₂(SO₄)₃ · 8H₂O (V), and Nd₂(SO₄)₃ · 4H₂O (VI) formed in sulfuric acid and fluorine-containing solutions during the synthesis of materials from feedstocks and the purification and separation of metals were separated. The regions of their existence were schematically presented. Particles with a “core-shell” structure were detected. The compounds were studied by elemental, crystallooptic, X-ray diffraction, and thermal analyses. The composition was determined for phase III (from thermogravimetric (TG) data) and spherolith-like particles of H₆NdF_7.8(SO₄)_0.5 · 3.75H₂O (VII) (by X-ray diffraction microanalysis). Freshly separated particles evolved HF. Phase IV corresponding to NdTiF₃(SO₄)₂ · 6H₂O (according to TG data) acquired the composition and form of the known NdTiOF(SO₄)₂ · 6H₂O phase after storage.

Extraction of scandium and concomitant elements: titanium, zirconium, thorium, iron, and vanadium from solutions of hydrochloric, nitric, and sulfuric acids with mixed trialkyl phosphine oxide has been studied. It has been shown that the phosphine oxide can be used for scandium preconcentration processes. It has been found that scandium recovery from hydrochloric acid solutions is rather selective and can be performed from solutions containing at least 2 mol/L HCl. When this reagent is used for scandium recovery from nitric acid solutions, the main extracted element is thorium; scandium can be separated from iron(III) and vanadium upon extraction from sulfuric acid solutions, while separation from zirconium can be provided by back extraction with diluted sulfuric acid.