Vol 64, No 9 (2019)

A series of Ln^III\({\text{Ga}}_{{0.{\text{5}}}}^{{{\text{III}}}}\)\({\text{Sb}}_{{{\text{1}}.{\text{5}}}}^{{\text{V}}}\)O₆ (Ln = La–Tb) complex oxides were prepared by coprecipitation followed by annealing. The phases where Ln = Ce, Pr, Eu, and Tb were prepared for the first time. The 900°С isothermal section of the Ce₂O_x–Ga₂O₃–Sb₂O_y phase diagram was plotted. Structures were calculated by the Rietveld method to show that all of the LnGa_0.5Sb_1.5O₆ (Ln = La–Tb) compounds have rosiaite (PbSb₂O₆) type structures. By the way of example, for LaGa_0.5Sb_1.5O₆ the isobaric heat capacity was determined and thermodynamic functions (entropy, enthalpy increment, and reduced Gibbs energy) were calculated at temperatures in the range from 15 to 1300 K.

A powder of monetite СаНРО₄ with a particle size of 100–300 nm was synthesized from monocalcium phosphate monohydrate Ca(H₂PO₄)₂ ⋅ H₂O and calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ in an acetone medium upon mechanical activation in a planetary mill. According to X-ray powder diffraction data, after heat treatment in the range 900–1100°С, the phase composition of the samples was represented by calcium β-pyrophosphate β-Ca₂P₂O₇. The synthesized powder can be used for producing resorbable calcium phosphate ceramic materials.

A novel azido complex of manganese(III) porphyrin with 1-methylimidazole has been synthesized. This complex can be abbreviated as [Mn^III(THMPP)N₃(1-MeIm)], where THMPP  is  5,10,15,20-tetrakis(4-hydroxy-3-methoxyphenyl)porphine and 1-MeIm is 1-methylimidazole. The complex has been characterized by UV-visible, FT-IR, ESI-MS spectra, elemental analysis, and magnetic susceptibility. The tentative structure has been proposed to be octahedral. The catalytic activity of the complex synthesized has been studied using different oxidants in the selective oxidation of aromatic alcohols to aldehydes. The selectively transformed products have been obtained under room conditions and short time period in high yields.

Isovalent analogues of the composite catalyst Na/W/Mn/SiO₂ prepared by solid-phase reactions, namely, Li/Na(Rb)/W/Mn/SiO₂, Na(Li,Rb,Cs)/Mo/Mn/SiO₂, Na/W/Re/SiO₂, Na/W/Mn/GeO₂, and a nonisovalent analogue Mg(Ca,Sr,Ba)/W/Mn/SiO₂ were studied by X-ray powder diffraction. The composites Li/Na/W/Mn/SiO₂ and Li/Rb/W/Mn/SiO₂ having an equimolar contents of alkali elements with nonadditive changes in SiO₂ matrix polymorphism and the formation of mixed tungstates show equally high product yields (23–24%) in oxidative coupling of methane (OCM), these yields being comparable to those observed for Na/W/Mn/SiO₂. Substitutions of W by Mo, Mn by Re, and Si by Ge in the composite Na/W/Mn/SiO₂, as well as substitutions of Na by Mg, Ca, Sr, and Ba, change the phase constitution of the composite and reduce its catalytic activity.

The new complexes [M(NA)₂(H₂O)₄]SiF₆ ⋅ 2H₂O, where M²⁺ = Co, Ni, Zn (complexes I, II, and III, respectively), and NA = C₆H₆N₂O is nicotinamide, [Cu(NA)₂(SiF₆)(H₂O)₂] ⋅ 2H₂O (IV), and (HNA)₂SiF₆ (V) have been synthesized from aqueous solutions and studied by chemical, IR spectroscopic, and X-ray diffraction analyses. Their unit cell parameters are a = 16.2448(18) Å, b = 6.8834(8) Å, c = 10.0767(11) Å, β = 102.765(3)°, V = 1098.92 ų, space group C2 for I; a = 16.1591(7) Å, b = 6.8777(3) Å, c = 10.0314(5) Å, β = 102.410(1)°, V = 1088.82 ų, space group C2 for II; a = 16.2265(6) Å, b = 6.8965(3) Å, c = 10.0696(5) Å, β = 102.390(1)°, V = 1100.60 ų, space group C2 for III; a = 6.5915(4) Å, b = 7.7670(4) Å, c = 10.1506(5) Å, α = 110.7390(10)°, β = 105.824(2)°, γ = 95.448(2)°, V = 456.868 ų, space group P\(\overline{1}\) for IV; and a = 14.1904(7) Å, b = 9.0468(4) Å, c = 11.8160(7) Å, β = 106.277(2)°, V = 1456.1 ų, space group C2/c for V. Complexes I–III are isostructural and represent ionic compounds formed by hexafluorosilicate anions and complex cations. The coordination polyhedron of the metal is a slightly distorted octahedron built of the O atoms of four coordinated water molecules and the two N atoms of two pyridine rings of two nicotinamide molecules in trans positions of the polyhedron. Complex IV has a polymeric chain structure. The coordination polyhedron of the copper cation represents an octahedron, which is elongated along its axis and built of the two N atoms of two pyridine rings of two nicotinamide molecules, the two O atoms of coordinated water molecules, and the two F atoms of hexafluorosilicate anions acting as bridges between neighboring cations. In the structure of complex V, the nitrogen atom of the pyridine ring HNA⁺ is protonated. The geometry of hexafluorosilicate anions is identical in all the five complexes. The structures have branched networks of hydrogen bonds.

Synthesis procedures have been developed for new supramolecular xylaratogermanate salts with different cations: (HPhen)₄[(OH)₂Ge₂(µ-HXylar)₄Ge₂(µ-OH)₂] · 13H₂O (I), [Fe(Phen)₃]₂[(OH)₂Ge₂(µ-HXylar)₄Ge₂(µ-OH)₂] · 6H₂O · C₂H₅OH (II), [Ni(Phen)₃]₂[(OH)₂Ge₂(µ-HXylar)₄Ge₂(µ-OH)₂] · 8H₂O (III). The compounds have been studied by X-ray diffraction, IR spectroscopy, and thermogravimetry. Their molecular and crystal structure has been determined. Compounds I–III include the same tetrameric μ-dihydroxyxylaratogermanate anion [(OH)₂Ge₂(µ-HXylar)₄Ge₂(µ-OH)₂]^4– with ditopic ligand, in which one of three hydroxyl groups does not coordinate to germanium(IV) but forms intramolecular hydrogen bond.

Complexes [Ln₂(H₂O)₆(μ₂-Htba−O,O')₄(Htba−O)₂]_n (Ln = Tb (I), Gd (II), Nd (III); and H₂tba is thiobarbituric acid) have been synthesized. According to single-crystal X-ray diffraction, monoclinic crystals of I–III are isostructural. They contain three independent Htba^– ions (one terminal and two bridging) and two independent Ln³⁺ ions. Six Htba^– ligands (two terminal and four O,O'-bridging) and two water molecules are coordinated to one Ln³⁺ ion, and four O,O'-bridging Htba^– ions and four water molecules are coordinated to the other Ln³⁺ ion to form square antiprisms. The antiprisms are bound by Htba^– bridging ions into layers. Numerous hydrogen bonds and π–π interactions stabilize the structures of the compounds. Thermal decomposition of complexes I and II performed in air results in mixtures of oxides and oxysulfates, whereas complex III forms Nd₂O₂SO₄.

The band structures of (15, 10), (21, 0), (16, 8), (18, 6), and (12, 12) WS₂ nanotubes of various chirality and diameter have been calculated by the linearized augmented cylindrical wave method in order to elucidate the extent to which they meet the requirement for sunlight water splitting catalysts. It is expected that the introduction of impurities and structural defects should increase the activity of the photocatalyst as compared with perfect tubes.

The compounds DyInGe₂O₇ and HoInGe₂O₇ were synthesized by multistage calcination of stoichiometric mixtures of the constituent oxides (solid-phase synthesis) in air in the temperature range 1273–1473 K. The high-temperature heat capacities of polycrystalline samples of dysprosium–indium and holmium–indium mixed-cation germanates were measured by differential scanning calorimetry. The thermodynamic properties of the investigated oxides were calculated using the C_p = f(T) experimental data.

Physicochemical analysis was shown to be efficient for developing and studying deicing agents. A methodology to design new deicing agents was described, which includes a criterion to choose salts, a method to investigate phase equilibria in water–salt systems (visual polythermal analysis), and determination of the deicing properties of salts and salt mixtures (eutectic temperature and ice-melting ability). A criterion to quantify the efficiency of deicing agents was proposed, which is the ice-melting ability of an agent at various temperatures. Data on phase equilibria in binary and ternary water–salt systems at temperatures below 0°C were presented, and so were data on the new developed deicing agents, including the compositions of the agents, the parameters of the eutectics formed with ice (temperature and concentration of solution), and the ice-melting ability of agents at temperatures of –5, –10, and –20°C.

The solubility was studied for compounds in the system Zr(SO₄)₂–K₂SO₄–H₂SO₄–H₂O in the section at 10 wt % H₂SO₄ under isothermal conditions at 25°C in the cuts at a constant solvent content of 60 wt % (H₂O + H₂SO₄). Equilibrium in the system was reached for 16 h while continuously stirring. In the section at 10 wt % H₂SO₄, equilibrium solid phases are the compounds K₂Zr(SO₄)₃ ⋅ 2H₂O, K₃Zr(OH)(SO₄)₃ ⋅ 2H₂O, K₆Zr(SO₄)₅ ⋅ 3H₂O, and β-K₂SO₄. The recovered compounds were investigated by X-ray powder diffraction, crystal optical, thermal analyses and IR spectroscopy. It was found that the solubilities of the potassium zirconium sulfates are much lower than those of the sodium zirconium compounds. The results are of practical importance for sulfuric acid treatment of eudialyte, a zirconium-containing mineral, huge reserves of which occur in the Kola Peninsula.

Activity coefficients are calculated for aqueous aluminum chloride and aluminum sulfate solutions at 298 K in terms of the generalized Debye–Hückel (DH) theory using experimental static dielectric permittivity versus concentration relationships. A semiquantitative fit of the experimental data is achieved; specifically, nonmonotonic activity coefficient versus concentration trends are reproduced. The applicability of the generalized Debye–Hückel theory to fit the thermodynamic properties of 3,1 and 3,2 valence type electrolytes is shown.