Žurnal neorganičeskoj himii

Mg-containing solid solutions based on Y2FeTaO7 and formed by various mechanisms of heterovalent substitution were synthesized and had the following compositions: Y2Fe0.55Mg0.3Ta1.15O7, Y2Fe0.625Mg0.3Ta1.075O7, Y2Fe0.7Mg0.3TaO7, Y2Fe0.7Mg0.2Ta1.1O7, Y2Fe0.85Mg0.15TaO7, Y1.85Mg0.15Fe0.925Ta1.075O7, and Y1.85Mg0.15FeTaO7. It was shown that all synthesized solid solutions have a pyrochlore-like layered structure (space group P3121), in which Fe3+ ions are distributed over three structural positions. The magnetic properties of these solid solutions are due to the presence of a small ferromagnetic component in a predominantly antiferromagnetic system and characterize a ferrimagnet or a canted antiferromagnet with the Néel transition at the Néel temperature TN above room temperature. According to the data of magnetic measurements, two magnetic phase transitions to the ordered phase occur in all the studied samples. Along with the TN transition, in weak magnetic fields and below TN, there is a second transition, which is most likely due to a spin reorientation of the Morin type. The existence of magnetic ordering at room temperature in one magnetic sublattice or an internal magnetic field (Hin) was confirmed by Mössbauer spectroscopy.

The reaction of a number of nitrilium derivatives of the closo-decaborate anion with hexamethylene- and nonamethylenediamine has been studied. It has been shown that the process proceeds with the functionalization of both amino groups of the nucleophile to form amidines of the type (Bu4N)2[B10H9NH=C(R)NH (CH2)nNH(R)C=NHB10H9] (R = CH3, C2H5, nC3H7; n = 6, 9). Target compounds have been characterized by high resolution multinuclear NMR and ESI mass spectrometry.

The behavior of borylated iminols based on the closo-decaborate and closo-dodecaborate anions in the dichloromethane–water system has been studied as a function of the pH of the aqueous phase. The distribution coefficients of compounds in the n-octanol–water system have been determined: for (Bu4N)[B12H11NHC(OH)CH3], log Kow = –0.46; for (Bu4N)[2-B10H9NHC(OH)CH3], log Kow = –0.51. These compounds show hydrophilic properties similar to those of formic and acetic acids. It has been shown that this method can be used to purify target compounds from hydrolysis products in the preparation of various derivatives as a result of nucleophilic addition of the closo-borate anions to nitrilium derivatives.

Arsenate phosphates 
 (1.75 ≤ x ≤ 3.0) were prepared by coprecipitation. Their unit cell parameter was a linear function of composition: a (Å) = 0.0967x + 11.873. The Na3Cr2(AsO4)2PO4 crystal structure was refined by the Rietveld method; the coordinates of basal atoms and bond lengths were calculated. A garnet solid solution crystallizes at 600–650°C; transition to a high−temperature rhombohedral structure occurred at 994–1044°C. The thermal expansion of the low-temperature phase having a garnet structure was studied in the range from –130 to 200°C. The solid solution samples expanded isotropically and had small thermal expansion.

The paper presents the results of studies of the self-propagating high temperature synthesis (SHS) of boron nitride via chemical reduction of boron oxide with aluminum in a nitrogen medium. The phase composition of the powder reaction products depending on the nitrogen pressure during the synthesis was studied by X-ray diffraction. It was found that SHS in the B2O3–Al system gives the BN–Al2O3 powder material containing 20–28 wt % hexagonal boron nitride depending on the nitrogen pressure. Microstructure examination showed that the obtained powder materials contains separate hexagonal BN particles with <3 μm size. The differences in the density and morphology of BN and Al2O3 determine the possibility of BN isolation from the obtained powder mixture by the pneumatic powder separation methods.

The process of cadmium(II) complexation with 1-ethyl-2-(4-methoxyphenyl)azobenzimidazole (L1), 2,2′-bipyridyl (L2), and 1,10-phenanthroline (L3) in the presence of the [trans-B20H18]2– anion has been studied. It has been found that the nature of the organic ligand affects the composition and structures of the resulting compounds. Complexation with ligand L1, a benzimidazole derivative, has yielded binuclear complex [CdL12NO3(μ-NO3)CdL1(NO3)2] (1), which contains no boron cluster anion. In the case of azaheterocyclic ligands L2 and L3, depending on the Cd : L ratio, heteroleptic complexes [CdL2NO3]2[trans-B20H18] (L = L2 (2); L3 (3)) with coordinated nitrate ions (Cd : L = 1 : 2) or tris-chelate complexes [CdL3][trans-B20H18] (L = L2 (4); L3 (5)) with the boron cluster anion as a counterion (Cd : L = 1 : 3) have been isolated. The structures of complexes [CdL12NO3(μ-NO3)CdL1(NO3)2] (1) and [Cd(L2)2NO3]2[trans-B20H18] (2) have been determined by X-ray diffraction.

Bismuth(III) hexamethylenedithiocarbamate (HmDtc) [Bi2{S2CN(CH2)6}6] (I) and its solvated with dimethyl sulfoxide form [Bi2(S2CNHm)6]⋅2(CH3)2SO (II) have been obtained. The crystal structure of compound I shows an unusual alternation of two unsymmetrical isomeric pseudo-binuclear [Bi1/1B(HmDtc)3···Bi1A/1C(HmDtc)3] molecules, each of which involves two non-equivalent mononuclear moieties combined by secondary Bi···S bonds. The solvation of complex I leads to the structural unification of isomeric [Bi(HmDtc)3] molecules followed by their self-organization into centrosymmetric pseudo-dimers in the structure of compound II. All HmDtc ligands coordinate in S,S'-anisobidentate mode to form four isomeric (in I) or structurally unique [Bi(HmDtc)3] molecules (in II), whose distorted polyhedra can be approximated by pentagonal pyramid or octahedron. Solvating DMSO molecules are retained in the structure II by C–H···O hydrogen bonds. The analysis of energy dispersive X-ray spectra allowed one to identify the residual matter obtained by thermolysis of the complexes as Bi2S3 with admixture of Bi0.

The band structures of two series of chiral single-walled gold nanotubes (5, n2) and (10, n2) have been calculated using the cylindrical wave method with inclusion of spin–orbit coupling. Compounds with high spin polarizability of the electronic structure and spin selectivity of conductivity have been revealed. They can be used as materials for design of molecular spintronics elements.

Pyrochlore-type neodymium and gadolinium zirconate hafnates have been prepared and identified. The heat capacities of the prepared samples have been measured by differential scanning calorimetry in the range 310–1800 K. Temperature-dependent cubic unit cell parameters have been determined and thermal expansion coefficients assessed in the range 298–1273 K using high-temperature X-ray diffraction. The thermal diffusivity of the samples was measured by the laser flash method, and the temperature-dependent thermal conductivity was calculated taking into account the porosity of the samples.

The cocrystallization of potassium, neodymium, and strontium sulfates from aqueous solutions has been studied using X-ray powder diffraction, thermogravimetry, energy-dispersive X-ray spectral analysis, and electron microscopy. Extensive solid solutions based on trigonal KNd(SO4)2⋅H2O have been found to exist in the concentration range 100–20 mol % of the KNd(SO4)2⋅H2O–SrSO4⋅0.5H2O system. The unit cell parameters of the solid solutions have been determined. Two phases have been discovered: trigonal KNd(SO4)2⋅H2O (space group P3121) and monoclinic KNd(SO4)2⋅H2O (space group P21/c1). The heterovalent substitution scheme 2Sr2+ → K+ + Nd3+ stabilizes the structure of solid solutions based on the isostructural KNd(SO4)2⋅H2O and SrSO4⋅0.5H2O trigonal phases.

Phase equilibria in sections of the Ca(NO3) system are investigated2–i-PrOH–H2O at temperatures below 0 °C and anti-icing properties of calcium nitrate and isopropanol compositions with a component ratio from 1 : 3 to 3: 1, temperatures, composition of eutectic with ice and melting ability of nitrate-isopropanol compositions at temperatures of -5 and -10 °C. Compositions characterized by good anti-icing properties have been identified.

The interaction of gold(III) complexes (Au(bipy)
, Au(phen)
, and Au(dien-H)Cl+) with human serum albumin (HSA) was studied in aqueous solutions (pH 7.4, CNaCl = 0.2 M, CAu = (2–10) × 10–5 M, CHSA < 6 × 10–4 M) at 25°C. In all cases, gold(III) is reduced to gold(I), which forms a complex with HSA. When an excess of HSA is present, the time required for complete transformation of the complexes does not exceed 1 h. In addition, it was shown that the redox reaction of gold(III) complexes with cysteine is much faster than the reaction with methionine.

For the first time, an analysis was made of the antioxidant properties of conjugates of CeO2 nanoparticles with human serum albumin (CeO2@HSA), including HSA isolated from blood plasma and biological fluids similar in composition to blood plasma, namely, peritoneal (ascitic) and synovial (articular) fluids. The antioxidant activity of hybrid nanomaterials was studied in relation to alkylperoxyl radicals by luminol-dependent chemiluminescence. It was shown that the interaction of CeO2 nanoparticles with purified human serum albumin is accompanied by a decrease in the antioxidant and prooxidant potential of albumin by a factor of ⁓1.5. Presumably, this is caused by the interaction of nanodispersed CeO2 with sulfhydryl groups of the protein. Conjugates of CeO2 nanoparticles with albumin isolated from biological fluids (CeO2@HSA) exhibit a synergistic antioxidant effect. In this case, the mechanism of antioxidant activity is fundamentally different from that for CeO2 sols modified with purified human serum albumin. According to quantitative assessment, the antioxidant capacity of CeO2@HSA conjugates is ⁓20 times lower than that of Trolox, a water-soluble analog of vitamin E.