Synthesis and crystal structure of the low-temperature modification of Li<Subscript>12</Subscript>Zn<Subscript>4</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>5</Subscript>

The crystal structure of a low-temperature modification of the Li₁₂Zn₄(P₂O₇)₅ compound has been determined by full-profile analysis from the X-ray powder diffraction data. The compound crystallizes in the monoclinic crystal system (a = 5.130(1) Å, b = 13.454(1) Å, c = 8.205(1) Å, β = 90.36(1)°, space group P2₁/n, Z = 4) and has a framework structure in which the zinc and lithium atoms statistically occupy equivalent positions.     

Synthesis and crystal structure of a new modification of sodium tetrahydroxyborate NaB(OH)<Subscript>4</Subscript>

A new polymorphic modification of sodium tetrahydroxyborate NaB(OH)₄ is synthesized and its crystal structure is determined. The compound crystallizes in symmetry space group P2₁2₁2₁ with the unit cell parameters a = 5.323(5) Å, b = 9.496(5) Å, and c = 6.596(5) Å. The discrepancy factor for 511 symmetrically nonequivalent reflections is R = 0.0188. Layers that are formed by boron tetrahedra, aligned parallel to the (010) planes, and alternate with layers of sodium cations can be distinguished in the structure.     

Crystal structure and thermal expansion of ammonium pentaborate NH<Subscript>4</Subscript>B<Subscript>5</Subscript>O<Subscript>8</Subscript>

Anhydrous ammonium pentaborate NH₄B₅O₈ has been synthesized by thermal dehydration of larderellite NH₄[B₅O₇(OH)₂] · H₂O at a temperature of 290°C for 7 h. The crystal structure has been determined from the X-ray powder diffraction data: a = 7.58667(5) Å, b = 12.00354(8) Å, c = 14.71199(8) Å, R _p = 6.23, R _wp = 7.98, R _B = 12.7, R _F = 8.95, and β-KB₅O₈ structure type. The double interpenetrating framework is formed by pentaborate groups, each consisting of a boron-oxygen tetrahedron and four triangles, in which all oxygen atoms are bridging. The thermal behavior of the NH₄B₅O₈ compound has been investigated using thermal X-ray diffraction. As for other pentaborates of this type, the thermal expansion of the NH₄B₅O₈ compound is anisotropic and reaches a maximum along the a axis. The thermal expansion coefficients are as follows: α _a = 39 × 10^?6, α _b = 6 × 10^?6, α _c = 20 × 10^?6, and α _V = 65 × 10^?6 °C^?1.     

Structure of a biologically active binuclear palladium complex,bis(bis[(μ<Subscript>2</Subscript>-cysteine)(2,2′-dipyridyl)-palladium(II)]) · hexanitrates · novemhydrates

The structure of a biologically active binuclear palladium complex, namely, [(dipy)Pd(μ-cysH) (μ-cys)Pd(dipy)]³⁺ · 3NO ₃ ^? · 4.5H₂O (dipy = 2,2′-dipyridyl, C₁₀H₈N₂; cys = cysteine, C₃H₇NO₂S), has been determined from X-ray diffractometry data. The compound crystallizes in the triclinic system, symmetry space group P1, with the unit cell parameters a = 13.863(1) Å, b = 13.819(1) Å, c = 12.170(1) Å, α = 122.13(1)°, β = 103.61(1)°, γ = 91.40(1)°, V = 1887.02 ų, Z = 2, and ρ = 1.82 g/cm³. The final discrepancy factor is R1 = 0.0495 for 12884 symmetrically nonequivalent reflections with F ₀ ≥ 4σ(F ₀), wR2 = 0.1071, and GooF = 0.978. The unit cell contains two chemically equivalent but crystallographically independent positively charged binuclear palladium complexes, six NO ₃ ^? anions, and nine water molecules. The π-π stacking interaction between the nearest pyridyl rings of the neighboring layers takes place. Moreover, the interlayer and intralayer interactions occur through van der Waals interactions and a complex three-dimensional system of hydrogen bonds, which are formed by water molecules, NH ₃ ⁺ groups, and carboxyl groups.     

Effect of nitrogen to niobium atomic ratio on superconducting transition temperature of δ-NbN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> powders

Powders of cubic niobium nitride δ-NbN _x with a particle size of below 20 μm were prepared by reactive diffusion at T = 1455?1475°C under nitrogen pressures of P ₁(N₂) = 0.1?3 MPa and P ₂(N₂) = 25 MPa. For these powders, the values of the stoichiometric coefficient x, lattice parameter a, and the superconducting transition temperature Tc were measured and the a(x), T _c(x) and T _c(a) functions were analyzed. The T _c values were found to linearly grow with increasing a (decreasing structure imperfection). A maximum value of T _c (15.8 K) corresponded to a maximum value of a (4.3934 Å). Maximain the a(x) and T _c(x) curves were found to correspond to a slightly substoichiometric nitride with x = 0.98. Having synthesized cubic niobium nitrides with 0.892 < x < 1.062, we managed to measure the dependences of a and T _c on x all over the almost entire homogeneity range for δ-NbN _x . Our a(x) and T _c(a) functions were found to reasonably agree with those previously reported for SHS-produced δ-NbN _x powders.     

Crystal structure of Pb<Subscript>6</Subscript>O[(Si<Subscript>6</Subscript>Al<Subscript>2</Subscript>)O<Subscript>20</Subscript>]

The crystal structure of Pb₆O[(Si₆Al₂)O₂₀)] is investigated using X-ray diffraction. The compound has tetragonal symmetry, space group I4/mmm, a = 11.7162(10) Å, c = 8.0435(12) Å, and V = 1104.13(2) ų. The structure is refined to R ₁ = 0.036 for 562 unique reflections with [F ₀] ≥ 4σF. The structure contains two symmetrically independent positions of the Pb²⁺ cations coordinated by five O atoms (Pb²⁺-O^2? = 2.34–2.68 Å). The TO₄ tetrahedra (T = Si, Al) form tubular [(Si₆Al₂)O₂₀] chains extended along the c axis. The O₄ oxygen atom is not bonded to the Si and Al atoms and is octahedrally coordinated by six Pb atoms with the formation of an oxo-centered OPb₆ octahedron. The assumption is made that, in some of lead silicate and aluminosilicate glasses, a number of oxygen atoms are located outside the tetrahedral structure and represent segregation centers of the Pb²⁺ cations due to the formation of oxo-centered complexes.     

Structure of a biologically active binuclear palladium complex in the compound bis(bis[(μ<Subscript>2</Subscript>-2-chloroethylammonium) (1,10-phenanthroline)-palladium(I)]) · octanitrates · dihydrates

The structure of a biologically active binuclear palladium complex, namely, [(1,10-phenanthroline) Pd(μ₂-2-chloroethylammonium) ₂ ⁴⁺ · 4NO ₃ ^? · H₂O, has been determined using X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group of symmetry Cc, with the unit cell parameters a = 24.527(3) Å, b = 13.097(1) Å, c = 22.651(3) Å, β = 104.23(1)°, V = 7052(2) ų, Z = 8, and ρ = 1.88 g/cm³. The final discrepancy factor is R1 = 0.0316 for 15581 symmetrically nonequivalent reflections with I ≥ 2σ(I), wR2 = 0.0513, and GooF = 1.047. The palladium atoms reside in the oxidation state of 1+, which is rarely encountered in organometallic compounds. The asymmetric part of the unit cell contains two chemically equivalent but crystallographically independent positively charged binuclear palladium complexes, eight NO ₃ ^? anions, and two water molecules. The π-π stacking interaction between the nearest 1,10-phenanthroline rings of the neighboring layers takes place. Moreover, the interlayer and intralayer interactions occur through electrostatic interaction forces and a complex three-dimensional system of hydrogen bonds, which are formed by water molecules and N ₃ ⁺ groups.     

Structure of a biologically active binuclear palladium complex in the compound (bis[(μ<Subscript>2</Subscript>-2-chloroethylammonium)(1,10-phenanthroline)-palladium(I)]) · tetranitrates · hydrate

The structure of a biologically active palladium complex [(1,10-phenanthroline)Pd(μ₂-2-chloroethylammoniu)] ₂ ⁴⁺ · 4NO ₃ ^? · H₂O has been determined from the diffractometric data. The compound crystallizes in the triclinic crystal system, space group of symmetry P \(\bar 1\), with the unit cell parameters a = 12.8352(8) Å, b = 14.4040(8) Å, c = 12.1668(9) Å, α = 116.16(1)°, β = 115.72(1)°, γ = 91.09(1)°, V = 1756.3 ų, Z = 2, and ρ = 1.892 g/cm³. The final reliability factor is R ₁ = 0.0351 for 7357 nonequivalent reflections with I ≥ 2σ(I), wR ₂ = 0.0970, and S = 1.044. The asymmetric part of the unit cell contains one positively charged binuclear palladium complex, four NO ₃ ^?1 anions, and one water molecule. The nanocomplexes are involved in the stacking π-π interaction by pairs: each complex forms a stacking with only one adjacent complex. The interaction between layers and inside each layer occurs through the van der Waals interactions and a three-dimensional system of hydrogen bonds, which are formed by the N ₃ ⁺ groups and water molecules.     

Solid Solution (AlN)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>(SiC)<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">x</Emphasis> ≈ 0.7) by SHS under High Pressure of Nitrogen Gas

Solid solution (AlN) _x (SiC)_1–x (x = 0.7) was prepared from Al–SiC mixtures by SHS under high pressure of nitrogen gas (50, 70 MPa) and characterized by XRD and SEM. Combustion product was found to have a wurtzite 2H structure with lattice parameters a = 3.10889 ± 0.00022 Å and c = 5.00741 ± 0.00080 Å.     

Synthesis and crystal structure of a new oxohalide CdPb<Subscript>2</Subscript>O<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

A new compound, CdPb₂O₂Cl₂, is synthesized by the method of solid-phase reactions. The compound has monoclinic symmetry, space group C2/m, a = 12.392(8) Å, b = 3.8040(14) Å, c = 7.658(5) Å, β = 122.64(5)°, and V = 304.0(3) ų. The structure contains one symmetrically independent position of the Pb²⁺ cation coordinated by three O^2? anions (Pb²⁺-O^2? = 2.29–2.34 Å) and five Cl^? anions (Pb²⁺-Cl^? = 3.35–3.57 Å). The Cd²⁺ cation has a symmetric coordination with the formation of two bonds Cd-O = 2.15 Å and four bonds Cd-Cl = 2.73 Å. The oxygen atom is tetrahedrally coordinated by three Pb²⁺ cations and one Cd²⁺ cation, which leads to the formation of oxo-centered heterometallic OPb₃Cd tetrahedra. The tetrahedra are linked together into chains through common Pb atoms and into layered complexes due to sharing of the equatorial Cd atoms. The chlorine atoms are located above the cavities of the oxo-centered layer.     

Structure of a catalytically active oxo-centered trinuclear cobalt complex triaqua-(μ<Subscript>3</Subscript>-oxo)-hexa(μ<Subscript>2</Subscript>-pivalato-O,O′)-tricobalt(III)

The structure of a catalytically active oxo-centered trinuclear cobalt complex, namely, [triaqua-(μ₃-oxo)-hexa(μ₂-pivalato-O,O′)-tricobalt(III)]¹⁺ · NO ₃ ^? · 3H₂O, has been determined using X-ray diffraction analysis. The compound crystallizes in the hexagonal crystal system, space group of symmetry P6₃/mmc, with the unit cell parameters a = 12.328(1) Å, c = 22.625(1) Å, V = 2978.1(4) ų, Z = 2, and ρ = 1.075 g/cm³. The final discrepancy factor is R1 = 0.0596 for 589 symmetrically nonequivalent reflections with I ? 2σ(I), wR2 = 0.1612, and GooF = 1.035. The high-symmetry complex [C₃₀H₆₀O₁₆Co₃]¹⁺ with symmetry D _6h and a diameter of ～11 Å is an oxo-centered trinuclear cluster consisting of three symmetrically equivalent Co(III) atoms. Among the oxo-centered trinuclear metal complexes known to date, this complex has the highest symmetry and differs by the presence of two chemically equivalent bridges between the metal atoms. Apart from the two positively charged symmetrically equivalent trinuclear complexes, the unit cell contains two symmetrically equivalent NO ₃ ^? ions (statistically disordered over four positions) and six crystal water molecules.     

Preparation,Infra-red,MAS-NMR and Structural Characterization of a New Copper Based Inorganic–Organic Hybrid Compound: [C<Subscript>5</Subscript>H<Subscript>6</Subscript>N<Subscript>2</Subscript>Cl]<Subscript>2</Subscript>CuCl<Subscript>4</Subscript>

The ionic salt [2(C₅H₆N₂Cl)⁺], [CuCl₄]^2? complex of copper(II) has been synthesized and characterized. The X-ray diffraction analysis with a single crystal of this compound showed that the title compound (4-amino-2-chloropyridinium)₂CuCl₄ [(CAP)₂CuCl₄], crystallized at room temperature in the monoclinic system, space group C_2/c (N°.15) and the following : a = 16.0064 (2) Å; b = 7.7964 (10) Å; c = 14.7240 (2) Å; β = 102.497 (10)°; V = 1793.91 (4) ų and Z = 4. The structure was solved by using 1,589 independent reflections down to R value of 0.021. The unit cell is made up of tetrachlorocuprate(II) anions and 4-amino-2-chloropyridinium cations linked together by an extensive hydrogen bond network of types N–H···Cl (N: pyridinium) and N–H···Cl (N: amine), and cation-lone pair of nitrogen element interactions. Solid state NMR spectra showed one and five isotropic resonances, ⁶³Cu and ¹³C, respectively, confirming the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for single crystal, revealed that the conduction in the material was due to a hopping process. This work aims to reveal the thermal properties of a new copper(II) based organic–inorganic hybrid and the conductivity properties that these compounds exhibit.     

The Crystal and Molecular Structure of Dianhydrogossypol

Dianhydrogossypol (4,4′-dihydroxy-5,5′-diisopropyl-7,7′-dimethyl-bis(3H-naphtho[1,8-bc]furan-3-one)) was made by refluxing gossypol in m-xylene. Proton NMR spectroscopy was used to confirm that complete conversion was achieved over a time period of several hours. Single crystals of the compound were obtained by slow evaporation from dichloromethane. Diffraction studies indicate that this crystal form is tetragonal with a I4₁/a space group and with cell dimensions of a = b = 33.8265(4) Å, c = 9.1497(2) Å, V = 10469.4(3) Å³ at 100 K. The structure was solved by direct methods and was refined to an R1 value of 0.0415 on 6,408 independent reflections. Dianhydrogossypol exists as a pair of enantiomers within this structure. The two fused planar ring systems are oriented at a 117° angle to each other (i.e., close to perpendicular), and the isopropyl groups are oriented with the ternary carbon hydrogen atoms pointed inward toward the center of the molecule. Repeating groups of four molecules (of the same chirality) pack to form a helical structure that is supported by intermolecular hydrogen bonds. Each helix is surrounded by four neighboring helices that are composed of molecules of the opposite chirality. The helices form the walls of empty channels that are 5–6 Å wide. As has been found for some gossypol crystal forms, the open-channel structure of dianhydrogossypol might be useful for scavenging or carrying small molecules. Additional NMR studies confirm that dianhydrogossypol can be converted directly to gossypol lactol ethers in the presence of anhydrous alcohols.     

Modeling Self-Organization Processes in Crystal Forming Systems. Symmetry and Topology Codes of Cluster Self-Assembly of Crystal Structure of Na<Subscript>44</Subscript>Tl<Subscript>7</Subscript> (Na<Subscript>6</Subscript>Tl)

The geometrical and topological analysis of the crystal structure of intermetallide Na₄₄Tl₇ (Na₆Tl, a = 24.154 Å, V = 14091.8 ų, space group F-43m) is carried out. The algorithms of the combinatorial-topological analysis, which ensure the recovery of the symmetrical and topological code (program) of the cluster self-assembly of the crystal structure of an intermetallide, are developed. The topological type of the basic 3D network for two types of cluster precursors corresponds to a simple cubic 3D network P _c with CN = 6 and basic 2D network of type 4⁴. There are eight cluster precursors in the unit cell: four K86 and four K50. The cluster precursor K86 made from 86 atoms is formed from eight icosahedra i-TlNa₁₂ linked by the apices. The center of the cluster precursor K86 is at the position 4a (0, 0, 0) with the point symmetry g = –43m. The 50-atomic cluster precursor K50 consists of six i-TlNa₁₂ icosahedra. The center of the cluster precursor K50 is in the partial position 4b (0, 0, 0) with the point symmetry g = –43m. The symmetrical and topological codes of the self-assembly of 3D structures from nanocluster precursors K86 and K50 are reconstructed in the following form: primary chain → microlayer → microframework.     

Perovskite-type MgCNi<Subscript>3</Subscript> superconductors as prepared by combined sintering-ETE process and SHS reaction: Structural and superconducting properties

Complete conversion of the elements into the Perovskite-type MgCNi₃ compound has been achieved in the following two-stage process: (1) isothermal treatment (sintering) of starting powder compacts and (2) their subsequent electrothermal explosion (ETE) under uniaxial pressure. For comparison, similar reaction was also performed by mere sintering and by SHS. The bulk anti-perovskite MgCNi₃ superconductor was prepared from Mg-C-3Ni powder compacts. Isothermal treatments failed in the formation of the perovskite-type compound as a sole product. The hexagonal MgCNi₃ phase obtained by combined sintering-ETE route was found to have the lattice constants a = 3.0845 Å and c = 3.5259Å. The grains of the MgCNi₃ obtained by sintering-ETE process are fine, well compacted, and more homogenous than those prepared by sintering or SHS. The structure of materials was characterized by XRD, SEM, and EDS. The superconducting properties were detected using the temperature dependence of magnetization M as measured in ZFC and FC experiments at H = 15 Oe. For our MgCNi₃, the superconducting transition temperature T _c is around 7 K.     

Cluster Self-Organization of Intermetallic Systems: Two-Layer Quasi-Spherical Nanocluster Precursors K69 and K26 in the Crystal Structure of Li<Subscript>26</Subscript>Na<Subscript>58</Subscript>Ba<Subscript>38</Subscript> (<Emphasis Type="Italic">cF</Emphasis>488)

The geometric and topological analysis of the crystal structure of intermetallic Li₂₆Na₅₈Ba₃₈ (cF488, a = 27.335 Å, V = 20 424 ų, F-43m) is carried out using computer methods (ToposPro software package). The analysis method is based on determining the chemical composition and structure of an intermetallic cluster precursor and constructing a basic 3D network of the structure in the form of a graph whose nodes correspond to the position of their centers of gravity. Using the method of the complete decomposition of the 3D factor graph of the crystal structure into cluster substructures, we find two types of framework-forming nanoclusters, namely, K69 of the 1@16@52 composition and K26 of the 0@4@22 composition with point symmetry g =–43m. The symmetric and topological code of self-assembly of 3D structures from nanocluster precursors is reconstructed in the following form: primary chain → microlayer → microframework. Clusters Ba5, Na₆(Na₄), and Na₂В are determined as spacers occupying voids in the 3D framework of nanoclusters K69 and K26.     

Crystal structure of new compound (Rb,K)<Subscript>2</Subscript>Cu<Subscript>3</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>2</Subscript>

A new compound of (Rb,K)₂Cu₃(P₂O₇)₂ is obtained by high-temperature reactions from a mixture of RbNO₃, KNO₃, Cu(NO₃)₂, and (NH₄)₄P₂O₇. The crystal structure was solved by direct methods and refined to R ₁ = 0.056 for 5022 independent reflections. The compound belongs to a rhombic crystal system, P2₁2₁2₁, Z = 8, a = 9.9410(7) Å, b = 13.4754(6) Å, c = 18.6353 (3) Å, and R = 0.056. The basis of the structure is a complex copper-phosphate skeleton of the composition of [Cu₃(P₂O₇)₂]^2–, which can be regarded as consisting of two types of heteropolyhedral layers parallel to the (001) plane. The layers are alternated with each other, forming a frame, in the cavities of which the positions of alkali cations are located, statistically populated with K⁺ and Rb⁺ ions. Based on the refined populations of the positions of alkali cations, an exact chemical formula of the compound can be written as Rb_1.28K_0.72Cu₃(P₂O₇)₂. The compound is the most complex among those known to this day of the composition of A₂ ^IB₃ ^II(P₂O₇)₂ (A = Li, Na, K, Rb, or Cs; B = Ni, Cu, or Zn).     

Structural characterization and superconducting properties of MgB<Subscript>2</Subscript> prepared by SHS-method

Self-propagating high-temperature synthesis (SHS) of bulk MgB₂ superconductor from Mg-2B powder blend is reported. This reaction proceeds violently at 100 A under a protective atmosphere. Since the heat of reaction of Mg and B was not enough for chain reaction, then (Ti + C) mixed powders were used as the ignition agent to assist the reaction (Mg + 2B). In this case, the combustion front moved without any difficulty. The diffraction lines of the product can be indexed to a hexagonal MgB₂ phase, with lattice constants a = 3.0845 Å, and c = 3.5259 Å. For comparison, the direct synthesis of (Mg + 2B) mixture was carried out at (800°C–1000°C). It can be found, that high-temperature sintering (1000°C) will induce the formation of impurities. The MgB₂ grains are fine, well compacted and more homogenous. The structure of materials was studied using XRD, FESEM and EDX. M-H curvatures were measured under the magnetic fields between ?80 kOe and 80 kOe. J _c was calculated from width of magnetization hysteresis loops based on the extended Bean Model.     

Three New Metal(II) Complexes with Unusual 2D Hydrogen Bond Network Based on <Emphasis Type="Italic">N</Emphasis>-methylimidazole

Three new metal(II) complexes based on N-methylimidazole, [ML₆]·(SH)₂·(H₂O)_2, (M = Ni(II) (1), Co(II) (2), Cu(II) (3), L=N-methylimidazole), have been synthesized and characterized. The single crystal X-ray structural analyses show that complexes 1, 2, and 3 have isomorphous structures and crystallize in monoclinic system with space group P2₁/c. The complexes containing isolated SH^? anions, which may come from the thermochemical sulfate reduction, are located in the gap with lattice water molecules and provide multiple intermolecular hydrogen bonds to form 2D layers. Topology analyses show a 2D hydrogen bond network, which can be regarded as an unprecedented trinodal (3,4,6)-connected topology with Schläfli symbol (3.4.5³.6)₂(3.4.5)₂(3²;5⁴;6⁴;8²;9³). Cyclic voltammetry and UV–vis spectra were studied.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.