Structure and electrical properties of crystalline and glassy Ag2PbP2O7

Single crystals of Ag₂PbP₂O₇ have been prepared by melting of the crystalline phase under phosphate flux. Ag₂PbP₂O₇, isotype of Na₂PbP₂O₇, is of triclinic symmetry with the space group P(−1) (Z=2). The unit cell parameters are: a=5.502(6) Å, b=7.008(8) Å, c=10.018(9) Å, α=106.63(6)°, β=93.89(7)°, γ=110,68(6)°. The lattice of Ag₂PbP₂O₇ consists of corner-shared structural units {Pb₂P₄O₁₄}⁴⁻, which form ribbons parallel to the [010] direction. The {Pb₂P₄O₁₄}⁴⁻ units result from the association of corner-shared PbO₅ polyhedra and P₂O₇ pyrophosphate groups. The ribbons are interconnected by Pb–O–P bridges in the [100] direction and form lamina parallel to (001) plan. Silver atoms are located between two alternating lamina. Glasses with the same composition as the crystalline phase have been synthesized. A study of transport properties of Ag₂PbP₂O₇ in the crystalline and glassy forms is reported.     

Crystal structure analysis of Y2Cu2O5

Single crystals of Y₂Cu₂O₅ were obtained in the flux growth process by controlled heating of a mixture of Y₂O₃, BaO, and CuO in a molar ratio of 1∶8∶20. These crystals were analyzed by a single-crystal X-ray diffraction analysis. The crystal contains polymeric chains of Cu₂O₅ interspersed by yttrium ions surrounded by octahedral arrangements of oxygen atoms. Crystal data: space group=Pna2₁,a=10.799(2) Å,b=3.4990(5) Å,c=12.459(2) Å,Z=4, 380 reflections,R=0.026,R _w=0.030.     

Structure and Some Properties of a Double Neptunyl(V) Cesium Molybdate,Cs[NpO<Subscript>2</Subscript>MoO<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)]

A double neptunyl(V) cesium molybdate, Cs[NpO₂MoO₄(H₂O)], was studied by single crystal X-ray diffraction. Crystal data: rhombic system, a = 9.478(2), b = 7.900(1), c = 10.499(2) Å; space group Pnna, Z = 4, d = 5.05 g cm^?3, R = 0.030. The compound has a framework structure; the coordination polyhedron of the Np atom is a distorted pentagonal bipyramid with the equatorial positions occupied by four O atoms of four molybdate groups and an O atom of the coordinated water molecule. The IR and visible absorption spectra of this compound and of Cs₂[(NpO₂)₂Mo₂O₈] whose structure had been determined previously were measured. The NpO ₂ ⁺ stretching vibration frequencies in the IR spectra of these compounds virtually coincide. Incorporation of the O atom of the Mo-O-Mo bridge into the first coordination sphere of the neptunyl(V) ion in Cs₂[(NpO₂)₂Mo₂O₈] exerts the same disturbing effect on the electronic absorption spectrum as does the cation-cation interaction with one of the O atoms acting as a bridge between two Np atoms.     

Crystal structure of β-Cs2Mo4O13

β-Modification of cesium tetramolybdate Cs₂Mo₄O₁₃ was prepared by hydrothermal reaction of lindgrenite Cu₃(MoO₄)₂(OH)₂ with a CsNO₃ solution. The compound crystallizes in the triclinic system, space group $P\bar 1β-Modification of cesium tetramolybdate Cs₂Mo₄O₁₃ was prepared by hydrothermal reaction of lindgrenite Cu₃(MoO₄)₂(OH)₂ with a CsNO₃ solution. The compound crystallizes in the triclinic system, space group P[`1]P\bar 1, a = 8.396(5), b = 8.655(5), c = 10.413(5) ?, α = 106.158(5)°, β = 103.686(5)°, γ = 109.761(5)°, V = 636.6(6) ?³. The Mo atoms are coordinated by O atoms to form strongly distorted MoO₆⁶⁻ octahedra. The Cs atoms coordinate nine O atoms each. Eight MoO₆⁶⁻ octahedra are combined in octamolybdate complexes by sharing common edges. These fragments, in turn, are linked in zigzag chains oriented along a-axis via peripheral octahedra sharing common edges. The compound is isostructural to the previously known alkali metal tetramolybdates A₂Mo₄O₁₃ (A = K, Rb), but differs essentially from α-Cs₂Mo₄O₁₃.     

Synthesis,characterization and crystal structure of a novel Strandberg-type polyoxoselenomolybdate Rb4[Se2Mo5O21]·2H2O

An inorganic compound formulated as Rb₄[Se₂Mo₅O₂₁]·2H₂O (1) has been isolated by conventional solution method and structurally characterized by single-crystal X-ray diffraction methods, scanning electron microscopy (SEM), powder XRD, IR, UV–vis spectra, and cyclic voltammetry measurements. This compound crystallizes in the monoclinic system, space group C2 with unit a = 19.701 (3) Å, b = 10.296 (2) Å, c = 12.134 (4) Å, β = 106.96 (2)° and Z = 4. The crystal structure of (1) is built up from a Strandberg clusters connected through hydrogen-bonding interactions into a three-dimensional supramolecular network.     

A new three-dimensional open-framework iron(III) phosphate, [C2N2H10][Fe2(HPO4)4]

A new open-framework iron(III) phosphate, I, [C₂N₂H₁₀][Fe₂(HPO₄)₄] has been hydrothermally synthesized in the presence of ethylenediamine (en). The structure is built up from the vertex linkages between the FeO₆ octahedra and the PO₄ tetrahedra, strictly alternating, forming the three-dimensional architecture. The linkages between the FeO₆ and PO₄ polyhedra gives rise to ladder-like edge-shared chains, which are connected variously forming two types of channels. The di-protonated en molecules occupy these channels. Crystal data for I, [C₂N₂H₁₀][Fe₂P₄O₁₆]: a=9.341(1), b=8.892(1), c=9.480(1) Å, β=117.6(1)°, V=698.1(1) ų, space group P2/n (No. 13), Z=2, M=557.7, D_calc=2.65 g cm⁻³, MoKα (λ=0.71073 Å), R₁=0.03, wR₂=0.08 and S=1.10. Magnetic susceptibility studies indicate a predominantly antiferromagnetic interaction with T_N=30 K.     

2D-network of inorganic-organic hybrid material built on Keggin type polyoxometallate and amino acid: [L-C2H6NO2]3[(PO4)Mo12O36]·5H2O

A new inorganic-organic hybrid material based on polyoxometallate, [L-C₂H₆NO₂]₃[(PO₄)Mo₁₂O₃₆]·5H₂O, has been successfully synthesized and characterized by single-crystal X-ray analysis, elemental analysis, infrared and ultraviolet spectroscopy, proton nuclear magnetic resonance and differential thermal analysis techniques. The title compound crystallizes in the monoclinic space group, P2₁/c_, with a = 12.4938 (8) Å, b = 19.9326 (12) Å, c = 17.9270 (11) Å, β = 102.129 (1)°, V = 4364.8 (5) Å³, Z = 4 and R₁(wR₂) = 0.0513, 0.0877. The most remarkable structural feature of this hybrid can be described as two-dimensional inorganic infinite plane-like (2D/∞ [(PO₄)Mo₁₂O₃₆]³⁻) which forming via weak Van der Waals interactions along the z axis. The characteristic band of the Keggin anion [(PO₄)Mo₁₂O₃₆]³⁻ appears at 210 nm in the UV spectrum. Thermal analysis indicates that the Keggin anion skeleton begins to decompose at 520 °C.     

Synthesis,structure and photocatalytic properties of <Emphasis Type="Italic">β</Emphasis>-ZrMo<Subscript>2</Subscript>O<Subscript>8</Subscript>

Monoclinic ZrMo₂O₈ was synthesized via solid state method and single crystals of the title compound have been grown by the hydrothermal method. The crystals belong to monoclinic crystal system with space group C2/c (No. 15) with a = 11·4243(19) Å, b = 7·9297(6) Å, c = 7·4610(14) Å and β = 122·15(2)°, Z = 4. The bandgap of the compound was 2·57 eV. Unlike the other polymorphs of ZrMo₂O₈, the monoclinic form has unique crystallographic features with ZrO₈ and Mo₂O₈ polyhedra. The photocatalytic activity of this compound has been investigated for the first time for the degradation of various dyes under UV irradiation and has been compared with the photoactivity of the trigonal form of ZrMo₂O₈. It has been observed that this compound exhibits specificity towards the degradation of cationic dyes.     

Crystal structure of K4[H2J2O10].8H20

Crystals of K₄ [H₂J₂O₁₀] 8H₂O belong to the triclinic system, space group P 1 with a = 7.161 (2) $\text{A}\text{?}\text{, b}\text{= 10,553}$ (5) $\text{A}\text{?}\text{, c}\text{= 7,081}$ (2) $\text{A}\text{?}\text{, α = 98°1′}$, β = 117°8′, γ = 90°6′ and Z = 1. The crystal structure has been determined on the basis of photographic data from 877 independent reflections, with the final R value of 6,6%. The iodine atoms are surrounded by a distorted octahedra consisting of five oxygen atoms and one OH group. The average J-O distance is 2.03 Å. There are 2 independent K atoms in the structure. K(1) has a coordination number of eight, while K(2) is surrounded by 6 (5 water molecules + one OH group) nearest neighbours.     

Hydrothermal synthesis and characterization of a zinc–cobalt phosphate microporous material

A new zinc–cobalt phosphate compound [Zn_(4−x)Co_x(PO₄)₂(HPO₄)][C₃H₄N₂]₃ (x≈0.25) (1) has been hydrothermally synthesized in the presence of imidazole as the template and crystallizes in the triclinic space group P−1 with crystal data a=9.6077(7) Å, b=9.8674(7) Å, c=12.3793(9) Å, α=77.569(4)°, β=78.040(4)°, γ=68.191(4)°, V=1053.52(13) ų, Z=2. Compound 1 exhibits an infinite two-dimensional layered structure, which is built up of {M₈P₆O₂₃} structural unit formed by vertex-sharing MO₄, MO₂N₂, MO₃N, PO₄ and PO₃(OH) (M=Zn, Co) moieties. A study of magnetic measurements indicates compound 1 has the well antiferromagnetic behavior.     

New arsenates (V) NaKAl2O[AsO4]2 and Na2KAl3[AsO4]4

The title compounds have been synthesized by a solid state reaction route using a salt flux. Their crystal structures were determined from single crystal X-ray data. NaKAl₂O[AsO₄]₂ crystallizes with the orthorhombic K₂Fe₂O[AsO₄]₂-type, Pnma, a = 8.2368(6) Å, b = 5.5228(3) Å, c = 17.0160(13) Å and Z = 4, whereas Na₂KAl₃[AsO₄]₄ crystallizes with the orthorhombic K₃Fe₃[AsO₄]₄-type, Cmce, a = 10.5049(9), b = 20.482(2), c = 6.3574(6) Å and Z = 4. The NaKAl₂O[AsO₄]₂ structure is built up of [Al₂As₂O₉]²⁻ layers perpendicular to the c-axis which are separated by A⁺ alkali layers. The [Al₂As₂O₉]²⁻ layers consist of ribbons of edge-sharing AlO₆ octahedra, running along the a direction and which are connected through AsO₄ tetrahedra by sharing corners. The Na₂KAl₃[AsO₄]₄ structure contains [Al₃As₄O₁₆]³⁻ layers perpendicular to the b-axis separated by A⁺ alkali layers. The [Al₃As₄O₁₆]³⁻ layer consists of a layer of corner-sharing AlO₆ octahedra which are also connected to the AsO₄ tetrahedra by sharing corners.     

Oxygen deficiency and formation of a new ordered perovskite-based structure Sr(Sr0.5Sb0.5)O3−y

A new oxygen-deficient and ordered perovskite-type structure with the formula Sr(Sr_0.5Sb_0.5)O_3−y has been synthesized readily by a solid state reaction in air at 1200°C. The structure of the Sr(Sr_0.5Sb_0.5)O_3−y phase as determined by Rietveld analysis using X-ray diffraction data, corresponds to an ordered perovskite with face-centered cubic symmetry, space group Fm3m (no. 225) and lattice parameters, a=8.3136(3) Å, V=574.602(3) ų and Z=8. An important structural feature of Sr(Sr_0.5Sb_0.5)O_3−y is the oxygen deficiency and the displacements of oxygen atoms from their ideal positions toward the Sb⁵⁺ cations. This fact leads to an alternating arrangement of larger [SrO₆] and smaller [SbO₆] octahedra (B-sites), the remaining Sr²⁺ being in the larger 12-fold coordinated A-sites. The thermal stability of the Sr(Sr_0.5Sb_0.5)O_3−y phase is pointed out, its melting point being 1480°C, and the subsequent quenching giving rise to a glass material.     

Mo6 cluster-based compounds for energy conversion applications: comparative study of photoluminescence and cathodoluminescence

Abstract

We report the photoluminescence (PL) and cathodoluminescence (CL) properties of face-capped [Mo₆Xⁱ₈L^a₆]^2? (X = Cl, Br, I; L = organic or inorganic ligands) cluster units. We show that the emission of Mo₆ metal atom clusters depends not only on the nature of X and L ligands bound to the cluster and counter-cations, but also on the excitation source. Seven members of the A_xMo₆Xⁱ₈L^a₆ series (A = Cs⁺, (n-C₄H₉)₄N⁺, NH₄⁺) were selected to evaluate the influence of counter-cations and ligands on de-excitation mechanisms responsible for multicomponent emission of cluster units. This study evaluates the ageing of each member of the series, which is crucial for further energy conversion applications (photovoltaic, lighting, water splitting, etc.).     

Dehydration/amine intercalation in Zn(O3PR)–H2O phosphonates: the missing link,X-ray structure of Zn(O3PCH3)

The hydrothermal synthesis of colorless crystals of Zn(O₃PCH₃) was achieved using a solution of zinc nitrate and methylphosphonic acid (1:1) in water, in the presence of thiourea. The structure was determined by single crystal X-ray diffraction [monoclinic, space group P2₁/c (No. 14), a=8.7226(9) Å, b=5.2156(7) Å, c=10.847(1) Å, V=389.48(9) ų, Z=2]. From this result, the mechanism of the structure modification taking place during the dehydration of Zn(O₃PR)–H₂O phosphonates was clearly demonstrated.     

Hybrid open frameworks: Hydrothermal synthesis and structure determination of MIL-33: a new vanadomethylendiphosphonate intercalating potassium cations

The hydrothermal synthesis and the ab initio structure determination from powder data of K₂(V^VO₂)₄(V^IVO){O₃P–CH₂–PO₃}₂–xH₂O (x=4) or MIL-33 are presented. MIL-33 crystallizes in the monoclinic system [space group C2/m (No. 12)] with lattice parameters a=4.8716(4) Å, b=14.614(1) Å, c=15.825(1) Å, β=94.06(1) Å, V=1123.8(2) ų, Z=2. MIL-33 is a mixed valence V^IV/V^V=1/4 vanadodiphosphonate. Its layered structure shows some potassium cations located both between the hybrid layers and in the eight-membered windows of the latter.     

Crystal structures of Ba4CaCu3O8+δ and Ba6CaCu3O10+δ

The crystal structures of the two ternary compounds, Ba₄CaCu₃O_8+δ and Ba₆CaCu₃O_10+δ, have been investigated by means of X-ray diffraction combined with Rietveld analysis. We found that the Ba₄CaCu₃O_8+δ phase has a cubic structure (Im–3m, a=8.1515(1) Å, δ=+0.8) for high oxygen content as reported in the literature but undergoes a transformation into a tetragonal structure (I4/mmm, a=8.1888(1) Å, c=8.0634(1) Å for δ=−0.3) when the oxygen content is lowered. The crystal structure of Ba₆CaCu₃O_10+δ (I4/mmm, a=4.0463(1) Å, c=21.7322(4) Å for δ=+0.2) is confirmed. Changes in the c value with sintering conditions suggest a variable oxygen content with no structure transformation.     

Synthesis,structure, and properties of the non-centrosymmetric borate Rb<Subscript>2</Subscript>CaB<Subscript>8</Subscript>O<Subscript>26</Subscript>H<Subscript>24</Subscript>

Single crystals of Rb₂CaB₈O₂₆H₂₄, a new non-centrosymmetric borate material, have been grown with sizes up to 8 × 5 × 3 mm³ by the slow evaporation of water solution at room temperature. The structure of the compound was determined by single-crystal X-ray diffraction. It crystallizes in the orthorhombic system, space group P2₁2₁2₁ with a = 11.5288(3) Å, b = 12.6334(4) Å, c = 16.6966(4) Å, Z = 4 and R ₁ = 0.0405, wR ₂ = 0.1043. Ultraviolet (UV)–vis spectrum transmission is performed on the Rb₂CaB₈O₂₆H₂₄, which shows an absorption edge about 195 nm in the UV region. Thermal properties were investigated by TG–DSC analysis. The powder second-harmonic generation (SHG) intensity measured by the Kurtz-Perry method indicates that Rb₂CaB₈O₂₆H₂₄ has about one-third of KDP (KH₂PO₄).The influence of different molar ratios and evaporation speed of water solution on crystal quality and size was also performed on the reported material.     

Synthesis,crystal structure and electrochemical properties of the manganese-doped LiNaFe[PO4]F materials

The new compounds LiNaFe_1−xMn_x[PO₄]F (x ≤ 1/4) were synthesized by a solid state reaction route. The crystal structure of LiNaFe_3/4Mn_1/4[PO₄]F was determined from single crystal X-ray diffraction data. LiNaFe_3/4Mn_1/4[PO₄]F crystallizes with the Li₂Ni[PO₄]F-type structure, space group Pnma, a = 10.9719(13), b = 6.3528(7), c = 11.4532(13) Å, V = 798.31(16) Å³, and Z = 8. The structure consists of edge-sharing (Fe_3/4Mn_1/4)O₄F₂ octahedra forming (Fe_3/4Mn_1/4)FO₃ chains running along the b-axis. These chains are interlinked by PO₄ tetrahedra forming a three-dimensional framework with the tunnels and the cavities filled by the well-ordered sodium and lithium atoms, respectively. The manganese-doped phases show poor electrochemical behavior comparing to the iron pure phase LiNaFe[PO₄]F.     

Crystal chemistry and redox behaviour of antimony strontium calcium perovskites

The compound Sr₂Sb_1.4Ca_0.6O₆ and their reduced forms Sr₂Sb_1.4Ca_0.6O_5.17 and Sr₂Sb_1.4Ca_0.6O_4.84 have been prepared and characterized by powder X-ray diffraction, electron diffraction, iodometric analyses and thermogravimetric analysis. The three phases with different oxygen stoichiometries are structurally related to the perovskite and show symmetry distortions from the ideal cubic structure (with cell parameter a_p). The crystal structure of Sr₂Sb_1.4Ca_0.6O₆ may be refined by the Rietveld method from powder X-ray diffraction data using the space group P2₁/n, and the cell parameters a=5.776(2), b=5.7837(2), c=8.1718(3) Å, β=90.039(3)° with the same structural model than for previously studied Sr₂Bi_1.4Ca_0.6O₆. It shows two crystallographically independent B positions with occupancies 100% Sb (site 1) and 40% Sb/60% Ca (site 2) ordered in a 3D NaCl-type arrangement. The reduced phases, Sr₂Sb_1.4Ca_0.6O_5.17 and Sr₂Sb_1.4Ca_0.6O_4.84, are obtained from Sr₂Sb_1.4Ca_0.6O₆ by treatment in Ar or Ar/H₂ at 650°C and show respectively the unit cell parameters a≈b≈5.9 Å, c≈8.4 Å (with possible space groups I2/m or Immm), and a=8.4 Å, b=6.0 Å, c=24.2 Å, β=125° (space group C2/c). The reduction process is reversible, and the initial oxidized phase can be obtained from the reduced ones by thermal treatment in oxygen or air, at temperatures close to 500°C.