Synthesis,structural, spectral,thermal and comparative biological activity studies of [V<Subscript>2</Subscript>O<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The hydrothermal reaction of a mixture of V₂O₅, VCl₃, 2,5-pyridinedicarboxylic acid and diluted H₂SO₄ for 68 h at 180°C gives a blue colored solution which yields prismatic blue crystals of IV ₂ ^IV O₂(SO₄)₂(H₂O)₆] (1) in 32% yield (based on V). Complex 1 was investigated by means of elemental analysis (C, H and S), TGA, FT-IR, manganometric titration, Single Crystal X-ray Diffraction Methods and also comparative antimicrobial activities. Crystal data for the compound: monoclinic space group P2₁/c and unit cell parameters are a = 7.3850(12) Å, b = 7.3990(7) Å, c = 12.229(2) Å, β = 108.976(12)° and Z = 2. Although structure of 1 as a natural mineral has been previously determined, this work covers new preparation method and full characterization of 1 along with comparison of antibacterial activity between 1 and the commercial vanadium(IV) oxide sulfate hydrate compounds, VOSO₄ · xH₂O (Riedel-de Haën and Alfa Aesar brand names). 1 was evaluated for the antimicrobial activity against gram-positive, gram-negative bacteria, yeasts and mould compared with the commercial VOSO₄ · xH₂O compounds. 1 showed weak activity against bacteria Bacillus cereus, Nocardia asteroides and yeast Candida albicans. A good antimicrobial activity was recorded against Cirtobacter freundii (15 mm). There are only a few reproducible well-defined vanadium(IV) starting materials to use for exploring the synthesis of new materials. VCl₄, VO(acac)₂, VOSO₄ · xH₂O and [V(IV)OSO₄(H₂O)₄] · SO₄ · [H₂N(C₂H₄)₂NH₂] are common starting materials for such applications. In addition to these compounds, 1 can be used as an oxovanadium precursor.     

Phase composition,formation parameters,and morphology of precipitates in the LiVO<Subscript>4</Subscript>-VOSO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system

The phase and chemical compositions of the precipitates formed in the LiVO₃-VOSO₄-H₂O system at initial pH within 1 ≤ pH ≤ 4 and 90°C were studied. The following phases were prepared: an α phase Li_1.4(VO)_1.3[H₂V₁₀O₂₈] · nH₂O and a β phase Li_{0.6 ? x} H_{1.4 + x} [V₁₂O_{31 ? y/2}] · nH₂O (0 ≤ x ≤ 0.5, 1.3 ≤ y ≤ 2.0) with a layered structure. Li_0.4V₂O₅ · H₂O nanorods with the interlayer distance 10.30 ± 0.08 Å were synthesized at 180°C in an autoclave. The morphology, IR spectra, and main formation processes for these polyvanadates were studied.     

Subsolidus phase relations in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Li<Subscript>2</Subscript>O-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> (Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>) systems

The phase composition has been studied and an equilibrium phase diagram has been designed for the Al₂O₃-Li₂O-R₂O₅ (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li₂O. New phases with the composition Li_1+x Al_1?x O_2?x , where x = 0–0.67, have been found.     

Effect of phosphate doping on electric properties and chemical stability of Ba<Subscript>4</Subscript>Ca<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>11</Subscript> protonic conductor

Conductivity of perovskite phosphate–substituted solid solutions of Ba₄Ca₂Nb_{2 –x} P _x O₁₁ (0.0 ≤ x ≤ 0.5) was studied as a function of temperature, partial pressure of oxygen and water vapors. It is proved that the studied systems are protonic conductors at the temperatures below 600°C in the atmosphere with elevated content of water vapors (pH₂O = 1.92 × 10^–2 atm). Introduction of the tetrahedral [PO₄] group in the complex oxide matrix of Ba₄Ca₂Nb₂O₁₁ results in an increase in the oxygen–ionic (dry air, pH₂O = 1.91 × 10^–4 atm) and protonic conductivities (wet air, pH₂O = 1.92 × 10^–2 atm). Is it found that the doping causes a considerable increase in chemical stability of phases with respect to carbon dioxide.     

Hydration and proton transport in solid solutions based on Ba<Subscript>2</Subscript>CaWO<Subscript>6</Subscript>

Hydrated alkaline-earth metal tungstates Ba₄Ca_{2 + x} W_{2 ? x} O_{12 ? 2x} with perovskite structure were studied by the thermogravimetry, ¹H NMR, IR, and Raman spectroscopy methods. Electrical conductivity and transfer numbers were measured with varying T, \(p_{O_2 } \) and \(p_{H_2 O} \). The solid solutions are capable of reversibly intercalating water and can exhibit high-temperature proton transport. The localization of protons on oxygen results in the appearance of energetically nonequivalent OH groups; a small fraction of protons are present in the form of H₂O and H₃O⁺.     

Sm<Subscript>2</Subscript>S<Subscript>3</Subscript>-Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> phase diagram

The Sm₂S₃-Sm₂O₃ phase diagram was studied by physicochemical methods of analysis from 800 K up to melting. Two oxysulfides are formed in the system: Sm₁₀S₁₄O with tetragonal crystal structure (space group I41/acd; unit cell parameters: a = 1.4860 nm, c = 1.9740 nm; microhardness: H = 4700 MPa; solid decomposition temperature: 1500 K) and Sm₂O₂S with hexagonal structure (space group P-3m1; a = 0.3893 nm, c = 0.6717 nm; H = 4500 MPa; congruent melting temperature: 2370 K). Within the extent of the Sm₂O₂S-based solid solution (61–70 mol % Sm₂O₃) at 1070 K, a singular point appears at the compound composition on property-composition curves. The eutectic coordinates: 23 mol % Sm₂O₃ and 1850 K; 80 mol % Sm₂O₃ and 2290 K.     

Coordination Chemistry of the Magic Inorganic Building Block {Fe<Superscript>II</Superscript>[Mo<Subscript>6</Subscript>P<Subscript>4</Subscript>O<Subscript>31</Subscript>]<Subscript>2</Subscript>}: Hydrothermal Synthesis and Crystal Structure of a New Reduced Ferrous Molybdophosphate

A new reduced ferrous molybdophosphate composite solid of the formula, [(C₁₀H₁₄N₂)H]₄[Fe^II ₁₀Mo^V ₂₄(H₂PO₄)₄(HPO₄)₁₂(PO₄)₄(H₂O)₁₆(OH)₁₆O₄₄]·12H₂O, has been synthesized from a reaction mixture of MoO₃, FeSO₄·7H₂O, C₂H₂O₄·2H₂O, nicotine, H₃PO₄, and H₂O under hydrothermal conditions. The crystal data: monoclinic, space group C2/m, a = 24.4349(124), b = 12.9935(66), c = 14.7281(74) Å, β = 104.87(1) Å, V = 4520(4) Å³, Z = 2, R ₁  = 0.0874, wR ₂  = 0.2179. The structure is built from the building blocks of the formula, {Fe^II[Mo₆P₄O₃₁]₂}, consisting of a network of MO₆ (M = Fe, Mo) octahedral and PO₄ tetrahedral linked through their vertices. The connectivity of the building blocks with two pairs of face-sharing dinuclear Fe(II) clusters of the formula of [Fe^II ₂(H₂O)₄O₅] on which a phosphate group is hanging gives rise to one-dimensional chains with eight-membered apertures. The remarkable hydrogen bonded interactions between the chains form a unique and interesting framework with three-dimensional intersecting tunnels where the protonated nicotine molecules as structuring templates and crystallization water molecules are situated.     

Systems Li<Subscript>2</Subscript>O(Na<Subscript>2</Subscript>O)-CdO-V<Subscript>2</Subscript>O<Subscript>5</Subscript>: Phase composition and phase diagrams

The subsolidus phase composition of the M₂O-CdO-V₂O₅ systems with M = Li or Na is studied. Double orthovanadates MCdVO₄ and MCd₄(VO₄)₃ form solid solutions of composition Li_{1 ? 2x/3}Cd _x/3CdVO₄ (0 ≤ x ≤ 1, orthorhombic space group Cmcm, modulation at x = 0.6) and Na_{3 ? 2x} Cd_{3 + x} (VO₄)₃ (0 ≤ x ≤ 0.10 and 0.30 ≤ x ≤ 1, orthorhombic space group Cmcm and Pn2₁ a or Pnma, respectively). In the range 0.10 < x < 0.30, the end-members of the solid solutions coexist. Isothermal sections of the systems are mapped.     

Thermodynamic calculations of phase equilibria in the neodymium-barium-copper-oxygen system at O<Subscript>2</Subscript> pressures of 0.21 and 1 bar

The analytic equations for the Gibbs energy of Nd-Ba-Cu-O system phases obtained earlier were used to calculate the phase diagrams of the Ba_0.5Cu_0.5O-Nd_0.5Cu_0.5O section at oxygen partial pressures of 0.21 and 1 bar. For p(O₂)= 0.21 bar, the coordinates of the nonvariant system points, the projection of the liquidus surface, and the phase diagram of the Nd_{1 + x} Ba_{2 ? x} Cu₃O_{6 + z} compound in the subsolidus region were determined.     

Crystal structures of <Emphasis Type="Italic">trans</Emphasis>-[Re<Subscript>6</Subscript>S<Subscript>8</Subscript>(CN)<Subscript>2</Subscript>L<Subscript>4</Subscript>] complexes,L = pyridine or 4-methylpyridine

The structures of three novel octahedral rhenium cluster compounds [Re₆S₈(CN)₂(py)₄]·H₂O (1), [Re₆S₈(CN)₂(4-Mepy)₄] (2), [Re₆S₈(CN)₂(4-Mepy)₄]·4-Mepy (3) (py = pyridine, 4-Mepy = 4-methylpyridine) are determined by X-ray crystallography. Crystal data are: C2/m space group, a = 14.813(1) Å, b = 14.772(1) Å, c = 9.2122(6) Å, β = 119.085(2)°, V = 1761.7(2) ų, d _x = 3.318 g/cm³, R = 0.0585 (1); I4₁/amd space group, a = 16.0018(3) Å, c = 14.7186(5) Å, V = 3768.81(16) ų, d _x = 3.169 g/cm³, R = 0.0489 (2); P2₁/c space group, a = 9.0452(4) Å, b = 15.8065(7) Å, c = 15.2951(6) Å, β = 103.700(2)°, V = 2124.57(16) ų, d _x = 2.957 g/cm³, R = 0.0245 (3). Molecular cluster complexes interact via π-π stacking affording 3D frameworks in 1 and 2 and chains in 3.     

Synthesis processes and transport properties of solid solutions in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-GeO<Subscript>2</Subscript>-V<Subscript>2</Subscript>O<Subscript>5</Subscript> system

The results of studies of solid solutions with the overall composition of Bi₄V_{2 ? x} Ge _x O_{11 ? δ} and Bi₄Ge_{3 ? x} V _x O_{12 + δ} are presented. The process of phase formation are studied during the synthesis of solid solution using the ceramic method and through liquid precursors. Crystallochemical parameters of the obtained compounds are determined. The size distribution of the particles is studied. Conductivity of annealed of polycrystalline samples as a function of temperature and composition is studied using the impedance spectroscopy method. The shape of impedance complex plane plots of the samples obtained in different ways is studied and analyzed.     

Theoretical modeling of the mechanism of aniline oxidation by singlet O<Subscript>2</Subscript>

The mechanism of aniline oxidation by singlet oxygen was studied by the DFT-PBE/L2 method. According to the calculations, aniline endoperoxide cannot participate in the reaction because of its energy instability. The addition of ¹O₂ to aniline proceeds with the simultaneous proton transfer to the oxygen molecule from the NH₂ group (for the syn-approach of oxygen) or from the aromatic ring (for the anti-approach). For the syn-approach of the ¹O₂ molecule, the HNC₆H₄(H)OOH intermediate is formed, whose decomposition leads to aniline p-hydroperoxide (predominantly) or p-iminoquinone. In the case of the anti-approach, the ¹O₂ molecule is inserted at the C–H bond to form aniline p-hydroperoxide (H₂NC₆H₄OOH). The decomposition of aniline p-hydroperoxide with the formation of p-aminophenol and H₂O₂ molecule proceeds via concerted mechanism.     

Thermal analysis on C<Subscript>6</Subscript>H<Subscript>10</Subscript>Ge<Subscript>2</Subscript>O<Subscript>7</Subscript>-doped MgB<Subscript>2</Subscript>

Additives to MgB₂ can improve the superconducting functional characteristics, such as critical current density (J _c) and irreversibility field (H _irr). Recently, we have shown that repagermanium (C₆H₁₀Ge₂O₇) is an effective additive, enhancing both J _c and H _irr. To look into details of the processes taking place during the reactive sintering, a thermal analysis study (0.167 K s^?1, in Ar) is reported. We used differential scanning calorimetry between 298 and 863 K and simultaneous thermogravimetric—differential thermal analysis between 298 and 1233 K. Samples were mixtures of powders with composition 97 mol% MgB₂ and 3 mol% C₆H₁₀Ge₂O₇. Up to 863 K, repagermanium decomposes by multiple steps and forms amorphous phases. A reaction with MgB₂ is not observed. Above this temperature, partial decomposition of MgB₂ occurs. Crystalline Ge and MgO are detected before formation of Mg₂Ge and MgB₄, when temperature approaches the melting point of Ge (1211 K). Carbon substitution for boron in the crystal lattice of MgB₂ is observed for samples heated above 863 K. The amount of substitutional C does not significantly change with temperature.     

Synthesis and magnetic properties of quasi-unidimensional oxide Sr<Subscript>6.3</Subscript>Rh<Subscript>2.35</Subscript>Mn<Subscript>2.35</Subscript>O<Subscript>15</Subscript>

Attempts of the synthesis in air of complex oxides Sr₃RhMnO_x and Sr₄Rh_1.5Mn_1.5O_x resulted in revealing formation of a new oxide phase Sr_6.3Rh_2.35Mn_2.35O₉ related to quasi-unidimensional family A_3n+3m A′ _n B_3m+n O_9m+6n at n = 1 and m = 1. Its structural characteristics and magnetic properties are studied. X-ray data of the obtained phase is indicated on the basis of trigonal cell (spatial group P321) with the parameters: a 9.6239(4) Å; c ₁ 4.1130(4) Å, c ₂ 2.4946(2) Å. Manganese and rhodium exist in the compound as the cations Mn⁴⁺, Rh³⁺ and Rh⁴⁺, as follows from the data of measuring of magnetic susceptibility in the range 2–300 K.     

High-temperature heat capacity of stannates Er<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript> and Tm<Subscript>2</Subscript>Sn<Subscript>2</Subscript>O<Subscript>7</Subscript>

Erbium stannate Er₂Sn₂O₇ and thulium stannate Tm₂Sn₂O₇ with a pyrochlore-type structure were produced by solid-phase synthesis by calcining stoichiometric mixtures of the respective oxides in air at 1473 K for 240 and 200 h. The high-temperature heat capacity of Er2Sn2O7 and Tm₂Sn₂O₇ was studied by differential thermal calorimetry at 353–1000 K. From the experimental dependences C _P = f(T), the thermodynamic functions (enthalpy change, entropy change, and reduced Gibbs free energy) of oxide compounds were calculated.     

Thermodynamic properties and functions of condensed Bi<Subscript>8</Subscript>O<Subscript>11</Subscript>

The values of ΔH°₂₉₈, S°₂₉₈, H°₂₉₈–H°₀, T, ΔH _fus, and C _p(T), as well as the temperature dependences of the Gibbs energy function, are calculated for Bi₈O₁₁ oxide by proven computational methods.     

Interactions in the Al<Subscript>2</Subscript>TiO<Subscript>5</Subscript>-Ti<Subscript>2</Subscript>O<Subscript>3</Subscript> System

Interactions in the Al₂TiO₅-Ti₂O₃ system were studied and the regions of existence of Al_2?2xTi _2x ³⁺ Ti⁴⁺O₅ solid solutions with a pseudobrookite structure were determined.     

CaCu<Subscript>3</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12</Subscript>-Based materials with variable copper content

The CaO-3 (1 + x)CuO-4TiO₂ system was studied using powder X-ray diffraction in the concentration region near calcium copper titanate. A single-phase material is formed in this system only when x ～ 0. An excess or deficit of copper gives rise to extra phases: CuO or CaTiO₃ and TiO₂, respectively. Impurities increase the dielectric constant of CaCu₃Ti₄O₁₂-based ceramics. An excess of copper oxide (x ～ 0.08) increases ? more than tenfold.     

The first chromate containing both Cr<Subscript>2</Subscript>O<Subscript>7</Subscript> and Cr<Subscript>3</Subscript>O<Subscript>10</Subscript> groups,bis(1,3-bis(4-piperidinium)propane) dichromate trichromate monohydrate: Synthesis and crystal structure

A new organic-inorganic hybrid material (C₁₃H₂₈N₂)₂[Cr₂O₇][Cr₃O₁₀]·H₂O (1) was synthesized by slow solvent evaporation at room temperature, and its crystal structure was determined by single crystal X-ray diffraction. This compound crystallizes in the monoclinic space group P2₁/c. The asymmetric unit contains two crystallographically independent 1,3-bis(4-piperidinium)propane, (H₂bppp)²⁺ cations (A and B), one trichromate Cr₃O ₁₀ ^2? anion, one dichromate Cr₂O ₇ ^2? anion, and one water molecule. All these entities are interconnected into a complicated two-dimensional hydrogen bonded network via N–H?O and O–H?O hydrogen bonds. Furthermore, this structure is stabilized by a large number of C–H?O interactions, thus establishing a three-dimensional network structure. This compound appears to be the first example of chromates containing both Cr₂O₇ and Cr₃O₁₀ groups.     

Synthesis and crystal structure of a supramolecular adduct of the aqua nitrato complex of gadolinium [Gd(NO<Subscript>3</Subscript>)(H<Subscript>2</Subscript>O)<Subscript>7</Subscript>]<Superscript>2+</Superscript> with macrocyclic cavitand cucurbit[6]uril

A supramolecular adduct of gadolinium aqua nitrato complex and cucurbit[6]uril { [Gd(NO₃)(H₂O)₇](C₅H₅N)@(C₃₆H₃₆N₂₄O₁₂)}(NO₃)₂·10H₂O is obtained by slow diffusion of methanol into an aqueous solution containing gadolinium nitrate, pyridine, and cucurbit[6]uril. According to single crystal X-ray diffraction data, water molecules coordinated to metal atom make hydrogen bonds to polarized carbonyl groups of the macrocycle. The heptaaquanitratogadolinium(III) [Gd(NO₃)(H₂O)₇]²⁺ cation is structurally characterized for the first time. Crystal system is triclinic, space group \(P\overline 1 \), a = 12.3137(4) Å, b = 14.2334(5) Å, c = 19.5629(6) Å; α = 80.850(1)°, β = 86.879(1)°, γ = 68.855(1)°; V = 3157.15(18) ų, Z = 2. Oriented hydrogen-bonded chains of alternating cucurbit[6]uril molecules and gadolinium aqua cations form in the crystal structure.