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.     

Phase equilibria in the system LaMnO<Subscript>3</Subscript>-SrMnO<Subscript>3</Subscript>-SrCrO<Subscript>4</Subscript>-LaCrO<Subscript>3</Subscript>

A continuous solid solution LaMn_1?y Cr _y O₃ with an orthorhombic structure is found to exist in the range of 0.0 ≤ y ≤ 1.0. An orthorhombic solid solution La_1?x Sr _x CrO₃ exists in the range of 0.0 ≤ x ≤ 0.1. The stability boundaries are determined for the perovskite phase La_1?x Sr _x Mn_1?y Cr _y O₃. An isobaric-isothermal section LaMnO₃-SrMnO₃-SrCrO₄-LaCrO₃ of the system La₂O₃-SrO-Mn₃O₄-Cr₂O₃ in air at 1100°C is designed.     

Crystal structures of Ti(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript> and Sn(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript>

The characteristics of crystal structures of the titanium(IV) diammonium (Ti(NH₄)₂P₄O₁₃) and tin(IV) diammonium (Sn(NH₄)₂P₄O₁₃) tetraphosphates, which are isostructural with similar silicon(IV) and germanium(IV) salts, have been obtained by the Rietveld method using X-ray powder diffraction data. The compounds crystallize in the triclinic system, space group P \(\overline 1 \), Z = 2, a = 15.0291(7) Å, b = 7.9236(4) Å, c = 5.0754(3) Å, α = 99.168(3)°, β = 97.059(3)°, γ = 83.459(3)° for Ti(NH₄)₂P₄O₁₃ and a = 15.1454(7) Å, b = 8.0103(5) Å, c = 5.1053(3) Å, α = 99.898(6)°, β = 96.806(3)°, γ = 83.881(4)° for Sn(NH₄)₂P₄O₁₃. The structure is refined in the isotropic approximation using the pseudo-Voigt function: R _p = 0.077, R _Bragg = 0.045, R _F = 0.057 for Ti(NH₄)₂P₄O₁₃; R _p = 0.082, R _Bragg = 0.044, R _F = 0.046 for Sn(NH₄)₂P₄O₁₃. The hydrogen atoms of the ammonium cations are placed in the calculated positions. A comparative analysis of the structures of the compounds of the M^IV(NH₄)₂P₄O₁₃ (M^IV = Si, Ge, Ti, Sn) series has been carried out.     

High-pressure defect phase Tm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

Perovskite-related oxide Tm _x Cu₃V₄O₁₂ (space group Im \(\bar 3\), Z = 2, a = 7.262?7.273 Å) with vacancies in the cationic sublattice has been prepared for the first time under barothermal conditions (p = 7.0?9.0 GPa, T = 900?1100°C). Electric resistivity (10–300 K) and magnetic susceptibility (0–300 K) were studied as a function of temperature. Tm _x Cu₃V₄O₁₂ is shown to have a metallic conductivity and paramagnetism.     

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.     

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-pressure defect phase Nd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

A perovskite-like oxide Nd _x Cu₃V₄O₁₂ (space group Im \(\bar 3\) Z = 2, a = 7.278–7.322 Å) with cationic vacancies was prepared for the first time under triaxial compression of p = 6.0–9.0 GPa at 700–1300°C. The compound has a metal-type conductivity, paramagnetic properties, and a phase transition.     

High-temperature heat capacity and thermodynamic properties of pyrovanadate Pb<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> and orthovanadate Pb<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The heat capacities of Pb₂V₂O₇ and Pb₃(VO₄)₂ as a function of temperature in the range 350–965 K have been studied by the differential scanning calorimetry method. The C_P = f(T) curve for Pb₂V₂O₇ is described by the equation C_p = (230.76 ± 0.51) + (73.60 ± 0.50)×10^-3T ? (18.38 ± 0.54)×10⁵T^-2 in the entire temperature range. For Pb₃(VO₄)₂, there is a well-pronounced extreme point in the C_P = f(T) curve at T = 371.5 K, which is caused by the existence of a structural phase transition. The thermodynamic properties of the oxide compounds have been calculated.     

Convenient regioselective reaction in presence of H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>: synthesis and characterization of pyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]quinoline-3,5-diones

We describe regioselective synthesis of pyrazolo[3,4-b]quinoline derivatives by multicomponent reaction of dimedone, 5-aminopyrazolone, and aromatic aldehydes in presence of H₃PW₁₂O₄₀ as catalyst. When this multicomponent reaction was investigated without catalyst under reflux conditions, a mixture of products was obtained, while the reaction successfully proceeded to formation of pyrazolo[3,4-b]quinoline in presence of H₃PW₁₂O₄₀. Good product yield, short experimental time, and low-cost catalyst provide convenient synthesis for formation of pyrazolo[3,4-b]quinoline pharmacological compounds.     

High-pressure defect phase La<Subscript>x</Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

Perovskite-like nonstoichiometric oxide La _x Cu₃V₄O₁₂ (space group Im \(\bar 3\), Z = 2, a = 7.313–7.354 Å) with cation-site vacancies has been prepared for the first time at high pressures (p = 6.0–8.0 GPa) and high temperatures (T = 700–1100°C). The compound has metal-type conductivity and paramagnetic properties, and undergoes a phase transition.     

Crystal Structure of New One-Dimensional Triple Molybdate Na<Subscript>2</Subscript>K<Subscript>2</Subscript>Cu(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The title compound (disodium dipotassium copper(II) tris-[molybdate (VI)]) is prepared by form melt and characterized by single crystal X-ray diffraction and UV-vis spectroscopy. It crystallizes in the triclinic space group P-1 with a = 7.4946(8) Å, b = 9.3428(9) Å, c = 9.3619(9) Å, α = 92.591(7)°, β = 105.247(9)°, γ = 105.496(9)°, V = 604.7 ų, and Z = 2. Its structure is isotypic with that of Na₄Mn(MoO₄)₃. It is formed by Cu₂O₁₀ distorted bi-octahedral dimers linked by two bridging bidentate Mo₂O₄ tetrahedra and, additionally, two monodentate Mo₁O₄ tetrahedra to form Cu₂Mo₄O₂₀ units. These units are linked by the insertion of Mo₃O₄ tetrahedra to build infinite ribbons disposed along the c axis. All of these ribbons form a one-dimensional framework. Both K1 and K3 cations are located in the inversion center, and all the other atoms are at general positions. The structure model is supported by the bond valence sum (BVS) and charge distribution CHARDI methods. The Cu²⁺ cations adopt the [4+2] CuO₆ Jahn-Teller distortion giving rise to an intense d–d transition in the UV-vis absorption spectra.     

Structure and properties of solid solutions based on bismuth niobate Bi<Subscript>3</Subscript>NbO<Subscript>7</Subscript>

Solid solutions Bi₃Nb_1–yW_yO_{7 ± δ}, Bi₃Nb_1–yV_yO_{7 ± δ}, Bi₃Nb_1–yFe_yO_{7 ± δ} (y = 0.1–0.5; Δy = 0.1), and Bi_3–xY_xNb_1–yW_yO_{7 ± δ} (x = 0.05, 0.1; y = 0–0.3; Δy = 0.1) have been studied. The homogeneity ranges of the solid solutions and crystal-chemical parameters have been determined by means of X-ray powder diffraction. The electrical conductivity of sintered samples has been studied by impedance spectroscopy. The joint introduction of yttrium and tungsten into the niobium sublattice does not lead to an increase in the conductivity of solid solutions, and the change of the dopant type has no noticeable effect on this conductivity.     

Refinement of LiFe<Subscript>5</Subscript>O<Subscript>8</Subscript> crystal structure

The crystal structure and the formation conditions of crystals of the LiFe₅O₈ ordered phase obtained from the solution-melt of the Bi₂O₃-Fe₂O₃-B₂O₃-LiCl quadruple system are refined. The crystals are black, octahedral, of cubic symmetry (space group P4₃32). Unit cell parameters: a = 8.3339(1) Å, V = 578.82(1) ų, Z = 4, d _calc = 4.753 g/cm³. From 6046 of the collected array I _hkl 358 are independent (R _int = 0.0321). As a result of anisotropic refinement of structural parameters, R ₁ factor is found to be 0.0186 (wR ₂ = 0.0467). Lithium atoms are in octahedral environment, Li-O is 2.109(1) Å; iron atoms are of two types: in octahedra with Fe-O (by two) distances of 1.9586(9) Å, 2.0152(9) Å, and 2.0652(10) Å and tetrahedra with Fe-O (three) 1.8848(10) Å and 1.914(2) Å. The structure is of inverted spinel type.     

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.     

Bismuth aluminoborate Bi<Subscript>0.96</Subscript>Al<Subscript>2.37</Subscript>(B<Subscript>4</Subscript>O<Subscript>10</Subscript>)O: Synthesis and crystal structure

The crystal structure of a new bismuth aluminoborate Bi_0.96Al_2.37(B₄O₁₀)O is studied by single-crystal X-ray diffraction. The Bi_0.96Al_2.37(B₄O₁₀)O single crystals are hexagonal (space group \(P\bar 6\) 2m). The unit cell parameters are as follows: a = b = 4.587(4) Å, c = 2.253(9) Å, α = β = 90°, γ = 120°, V = 168.60 ų, Z = 1.     

High-pressure nonstoichiometric phase Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

Perovskite-like nonstoichiometric oxide Sm _x Cu₃V₄O₁₂ (space group Im \(\bar 3\), Z = 2, a = 7.276?7.314 Å) with cationic vacancies and a homogeneity region was prepared barothermally (p = 6.0?9.0 GPa, T = 700?1100°C) for the first time. Structural and isotropic thermal parameters, as well as bond lengths and bond angles, were determined. The compound has metal-type conductivity and paramagnetic properties.     

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.     

Theoretical study of V<Subscript>20</Subscript>O<Subscript>50</Subscript> oxovanadate cluster compounds with alkali metal atoms

The energies and structural and spectroscopic characteristics of model М _n V₂₀O₅₀ systems corresponding to compounds of the V₂₀O₅₀ oxovanadate cluster with alkali metal atoms (M = Li, K; n = 1–20) have been calculated by the density functional theory method (B3LYP). It has been demonstrated that, in the K _n V₂₀O₅₀ compounds, all the metal atoms are coordinated in the outer sphere to the edges of the hollow dodecahedral V₂₀O₅₀ cage to form three-center O_t?K?O_t bridges with terminal oxygen atoms. In the Li _n V₂₀O₅₀ compounds, the metal atoms can be coordinated both outside and inside the V₂₀O₅₀ cage. At n = 4, the most favorable isomer is endohedral Li₄O₄@V₂₀O₄₆ in the quintet state (S = 5), in which the four Li atoms are located in the inner cavity of the inverted O₄@V₂₀O₄₆ isomer of the oxovanadate cluster with four O atoms oriented to the cage center and form with them a corrugated eight-membered ring Li₄O₄. The decrease in energy caused by the formation of the endohedral isomer (4Li + V₂₀O₄₅₀ → Li₄O₄@V₂₀O₄₆) is estimated at ~377 kcal/mol. The exohedral isomer 4Li ? V₂₀O₅₀ (S = 5), in which the Li atoms are coordinated to the outside of the V₂₀O₅₀ cage, is ~23 kcal/mol less favorable. For the other members of the Li series with n from 4 to 20, the endohedral isomers with the inner Li₄O₄ ring remain preferable. At n > 4, the extra Li atoms fill the outer sphere of the cage, being coordinated to its edges to form three-center O_t?Li?O_t bridges with terminal oxygen atoms. The specific energy of formation of Li _n V₂₀O₅₀ (by the scheme nLi + V₂₀O₄₅₀ → Li₄O₄@V₂₀O₄₆Li_n-4) per Li atom monotonically decrease from ~98 (n = 2) to ~80 kcal/mol (n = 20). For K _n V₂₀O₅₀, these energies are ~20?25 kcal/mol lower than for the lithium analogues and decrease from ~80 (n = 2) to ~64 kcal/mol (n = 12). The atoms of both alkali metals in the M _n V₂₀O₅₀ systems have large positive effective charges (0.85e?0.92e for K and 0.65e?0.78e for Li), which also monotonically decrease with increasing n. The addition of each alkali metal atom is accompanied by its ionization (М → М⁺) along with the reduction of one of the neighboring pentavalent vanadium atoms to the tetravalent state (V^V → V^IV) and localization of the unpaired electron in its 3d shell. For all Li _n V₂₀O₅₀ complexes, the states with maximal multiplicity and parallel spins are the most preferable.     

Synthesis and crystal structure of the new complex cobalt and nickel oxide Sr<Subscript>2.25</Subscript>Y<Subscript>0.75</Subscript>Co<Subscript>1.25</Subscript>Ni<Subscript>0.75</Subscript>O<Subscript>6.84</Subscript>

The complex cobalt and nickel oxide Sr_2.25Y_0.75Co_1.25Ni_0.75O_6.84 has been synthesized by the citrate method. The oxygen content of the oxide has been determined by iodometric titration. The crystal structure of the compound has been refined using X-ray powder diffraction data (a = 3.7951(2) Å, c = 19.700(1) Å, χ₂ = 1.15, R _F ² = 0.0586, R _p = 0.0365, R _wp = 0.0462). Sr_2.25Y_0.75Co_1.25Ni_0.75O_6.84 has the structure of the second member of the Ruddlesden-Popper series A _{n + 1}B_nO_{3n + 1}.     

Synthesis and crystal structure of strontium borate Sr<Subscript>4</Subscript>B<Subscript>14</Subscript>O<Subscript>25</Subscript>

The new compound Sr₄B₁₄O₂₅ (4SrO · 7B₂O₃) corresponding to an oxide ratio of 4: 7 has been identified and synthesized in the SrO-B₂O₃ system. The crystal structure of the compound has been determined (space group Cmc2₁, a = 7.734(5) Å, b = 16.332(5) Å, c = 14.556(5) Å, Z = 4, 702 F(hkl), R = 0.078). The borate anions form a three-dimensional framework consisting of borate groups of two types: three-ring structures (2□, Δ) and BO₃ triangles. Layers formed by 14-membered rings composed of boron-oxygen tetrahedra and triangles packed within the layer according to the herringbone pattern can be distinguished in the framework. The strontium atoms are located on the mirror symmetry planes between these layers. The compound is metastable and decomposes, on long-term storage, into strontium di- and metaborate.