Vol 62, No 6 (2017)

The synthesis of hydrolytically active heteroligand precursors of the composition [M(O₂C₅H₇)_x(ⁱOC₅H₁₁)_y] (M = Zr⁴⁺ and Y³⁺) using zirconium and yttrium acetylacetonates was investigated. It was shown that the reactivity of the obtained precursors in hydrolysis and polycondensation depends on the composition of the coordination sphere. It was studied how thin films of their solutions are applied by dip coating to the surface of Al₂O₃ substrates with platinum interdigital electrodes and a microheater. A study was made of the effect of the crystallization conditions and thickness of the oxide coatings of the composition 8 mol % Y₂O₃–ZrO₂ on their microstructure and sensor characteristics in oxygen detection.

A new two-step synthesis of Fe₃O₄@Au core–shell nanoparticles stabilized in polyethylene glycol is described. The nanoparticles were characterized by transmission electron microscopy, X-ray powder diffraction, UV and Mössbauer spectroscopy. Fe₃O₄@Au nanoparticles featured both optical properties (they featured a plasmon resonance band) and magnetic properties (they responded to an external magnetic field), typical of individual gold and magnetite nanoparticles, respectively.

We describe the effect caused by the modification of Nafion membranes with nanoparticles of rubidium and cesium acid salts of phosphotungstic and silicotungstic heteropoly acids (HPAs) using layer-by-layer casting on the properties of the membranes depending on the dopant type and the percent modified layer thickness. The ionic conductivity and diffusion permeability of hybrid materials have been studied. The modification is shown to increase the ionic conductivity at low relative humidity. The highest conductivity is observed for the membranes where the modified layer amounts to 35–50% of the total membrane thickness. On the contrary, diffusion permeability is reduced upon modification. Asymmetric ion transfer is observed: the ion transfer rate from the modified layer is lower than from the unmodified layer. This asymmetry arises from the anion concentration gradient in the membrane, which is directed from the modified to unmodified side of the membrane. An asymmetric membrane oriented so that its modified side faces the anode can potentially increase the power of a fuel cell.

The atomic structure of the layered nanocrystalline molybdenum disulfide compound with trimethylphenylammonium cations has been determined for the first time using X-ray powder diffraction analysis adapted for turbostratically disordered systems and quantum chemical density functional theory calculations. It has been demonstrated that, in this compound, a conducting modification of MoS₂ monolayers is stabilized, which is metastable under common conditions. Bonding interaction inside the molybdenum disulfide layers as well as between these layers and organic cations, revealed in the framework of Bader’s atoms in molecules theory, has been considered.

The lithium(I) catena-diaquabarbiturate complex [Li(H₂O)₂(HBA–O,O′)]_n (I), where Н₂ВА is barbituric acid, has been structurally characterized by X-ray diffraction (CIF file CCDC no. 1447689), and its thermal decomposition and IR spectrum have been studied. Crystals of complex I are monoclinic, a = 6.4306(7) Å, b = 16.720(1) Å, c = 7.1732(8) Å, β = 108.253(4)°, V = 732.5(1) ų, space group P2₁/c, and Z = 4. One independent μ₂-bridging HBA^– ligand is coordinated to two Li(I) ions via the two oxygen atoms of C₄₍₆₎=O carbonyl groups. Each Li⁺ ion is linked with two μ₂-HBA^– ions and two terminal water molecules at tetrahedron vertices. μ₂-HBA^– ions link tetrahedra into a chain. The structure is stabilized by multiple hydrogen bonds and π–π-interaction between HBA^–. The shift of ν(C=O) vibration bands in the IR spectrum of complex I in comparison with Н₂ВА towards lower frequencies agrees with the coordination of HBA^– via oxygen atoms. The dehydration of complex I occurs in two stages in the regions of 100–150 and 150–240°C.

New double complexes [Co(DMSO)₆][SiF₆] ⋅ 2H₂O (I) and [Co(DMF)₃(H₂O)₃][SiF₆] ⋅ DMF (II) have been synthesized and studied by IR spectroscopy and X-ray diffraction. Crystals of complex I belong to the tetragonal symmetry system, space group R3̄, Z = 3, a = 11.8232(3) Å, c = 18.4699(5) Å, V = 2235.97(10) ų, ρ_calc = 1.573 g/cm³. Crystals of complex II are triclinic, space group P1̄, Z = 2, a = 8.6264(4) Å, b = 10.1419(4) Å, c = 13.9657(6) Å, α = 100.847(2)°, β = 98.549(2)°, γ = 93.479(2)°, V = 1181.71(9) ų, ρ_calc = 1.539 g/cm³.

Association of sulfonated derivatives of cobalt phthalocyaninate in solutions in the presence of nitrogen-containing organic ligands is studied. Ligand denticity and spatial structure are found to be the main factors controlling the association equilibrium between sulfonated metallophthalocyanines.

The band structure of ten single-walled gold nanotubes of different radius and chirality angle have been calculated by the linearized augmented cylindrical wave method. For all tubes, the Fermi level crosses the half-filled band; therefore, the tubes are characterized by a metallic electronic structure. The band structure of the nanotubes changes relatively weakly with a change in nanotube structure. The valence band width for all the tubes is 9.1 eV. The density of states at the Fermi level remains unaltered with a change in chirality angle and decreases by 30% with an increase in radius from 3 to 12 Å.

Consideration was made of structural features of the liquidus and solidus hypersurfaces of the isobaric melting diagrams of quaternary systems with a single liquid phase and solid phases of constant compositions which undergo neither phase transitions nor decomposition into other phases while cooling. An intimate relationship between the topologies of such hypersurfaces was noted. The oriented graph of the liquidus hypersurface can be obtained from the graph of the solidus hypersurface by drawing arrows on its edges in the direction of decreasing temperature along the corresponding monovariant lines or by labeling its vertices with symbols of types of invariant reactions. An example was given for constructing different variants of the melting diagram of a system that correspond to the same topology of the solidus hypersurface.

The reactions of 1,4-dioxane-substituted closo-decaborate anion ([B₁₀H₉O₂C₄H₈]^–) with metal acetylenides, diethyl malonate, ethyl acetoacetate, triethyl orthoformate, acetylacetone, and malonodinitrile were studied. The reactions were shown to be accompanied with substituent ring opening and attachment of the corresponding pendant functional group. The obtained compounds were characterized by various physicochemical methods (IR and polynuclear NMR spectroscopy, ESI mass spectrometry).

Thermal behavior and thermodynamic characteristics of vanadyl β-diketonates—acetylacetonate VO(acac)₂, dipivaloylmethanate VO(thd)₂, and tris-hexafluoroacetylacetonate VO(hfa)₂ (Hacac, 2,4-pentanedione; Hthd, 2,2,6,6-tetramethyl-3,5-heptanedione; Hhfa, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione)—have been studied by thermal analysis and the Knudsen effusion mass spectrometry study of gas phase composition. The compounds have been shown to undergo congruent sublimation. Saturated vapor over the complexes has been shown to comprise monomeric VOL₂ molecules. Absolute values of partial pressures and sublimation enthalpies of these compounds have been determined.

Thermal decomposition of fluorooxalatozirconates (FOxZs) K₃ZrF₅C₂O₄, K₂ZrF₄C₂O₄ ⋅ 2H₂O, KZrF₃C₂O₄ ⋅ 3H₂O, and Zr₄O₃F₂(C₂O₄)₄ ⋅ 2H₂O in air flow is studied. Crystalline K₂ZrF₄C₂O₄ and KZrF₃C₂O₄ are detected. The decomposition onset temperature of anhydrous products goes down as the K/Zr molar ratio decreases. Disproportionation of potassium FOxZs both at the oxalate group yielding K₂ZrF₄C₂O₄ and ZrO_2–x/2F_x, K₂C₂O₄ and K₃ZrF₇ and at fluorine yielding K₃ZrF₇ and ZrO₂ takes place. FOxZs can be used as precursors to produce fine-grained ZrO₂ (baddeleyite).

Phase equilibria were studied at temperatures 475–520°C and a pressure to 130 MPa in the ternary system Na₂SO₄–NaCl–H₂O with boundary binary subsystems of two types. In type 1 subsystems (the NaCl–H₂O subsystem in this work), there are no critical phenomena in saturated solutions. Type 2 subsystems (the Na₂SO₄–H₂O subsystem in this work) have terminal critical points p (G = L – \({S_{N{a_2}S{O_4}}}\)) and Q (L₁ = L₂ – \({S_{N{a_2}S{O_4}}}\)). It was shown that the ternary system contains two regions of three-phase equilibria ((G–L–S) and (L₁–L₂–S)), divided by a two-phase fluid region (F – \({S_{N{a_2}S{O_4}}}\)), and two types of monovariant critical curves ((G = L – \({S_{N{a_2}S{O_4}}}\)) and (L₁ = L₂ – \({S_{N{a_2}S{O_4}}}\))). With increasing temperature, these three-phase regions approach each other until the two-phase fluid equilibrium vanishes and the monovariant critical curves meet at a binary homogeneous critical point (G = L–S ⇔ L₁ = L₂ – \({S_{N{a_2}S{O_4}}}\)) at a maximal temperature of ~495°C and a pressure of ~75 MPa.

Separate and concurrent extraction of palladium and europium from nitric acid and carbonate solutions with calix[4]- and thiacalix[4]arenes, their phosphorylated derivatives, and mixtures have been carried out. Charge state of sulfur and oxygen donor atoms in the extractants have been studied by XPS, XES, and quantum chemical calculations. It has been experimentally confirmed that the electronic structure of substituents at PO group has no effect of on the charge state of sulfur atoms in phosphorylated thiacalixarenes and assumption on the possible electronic effect of bridging sulfur atoms on the charge state of phosphoryl oxygen in bifunctional extractants has been made. These results substantiate the method of combined extraction of Pd and Eu from nitric acid solutions and their separation with factor 2 × 10³ upon carbonate back extraction of europium and are of interest for simplified (Purex) and promising (Carbex) processes.