Yb5Ni4Sn10 and Yb7Ni4Sn13: New polar intermetallics with 3D framework structures

The title compounds have been obtained by solid state reactions of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. Yb₅Ni₄Sn₁₀ adopts the Sc₅Co₄Si₁₀ structure type and crystallizes in the tetragonal space group P4/mbm (No. 127) with cell parameters of a=13.785(4) Å, c=4.492 (2) Å, V=853.7(5) Å³, and Z=2. Yb₇Ni₄Sn₁₃ is isostructural with Yb₇Co₄InGe₁₂ and crystallizes in the tetragonal space group P4/m (No. 83) with cell parameters of a=11.1429(6) Å, c=4.5318(4) Å, V=562.69(7) Å³, and Z=1. Both structures feature three-dimensional (3D) frameworks based on three different types of one-dimensional (1D) channels, which are occupied by the Yb atoms. Electronic structure calculations based on density functional theory (DFT) indicate that both compounds are metallic. These results are in agreement with those from temperature-dependent resistivity and magnetic susceptibility measurements.     

Synthesis and crystal structures of La3MgBi5 and LaLiBi2

Two new ternary bismuthides, La₃MgBi₅ and LaLiBi₂, have been prepared by solid-state reactions of the corresponding pure metals in welded niobium tubes at high temperature. Their structures have been established by single-crystal X-ray diffraction studies. La₃MgBi₅ crystallizes in the hexagonal space group P6₃/mcm (No.193) with cell parameters of , , , and Z=2. LaLiBi₂ belongs to tetragonal space group P4/nmm (No.129) with cell parameters of , ,, and Z=2. The structure of La₃MgBi₅ is of the ‘‘anti’’ Hf₅Sn₃Cu type, and features 1D linear Bi⁻ anionic chains and face-sharing [MgBi_6/2]⁷⁻ octahedral chains. The structure of LaLiBi₂ is isotypic with HfCuSi₂, and is composed of 2D Bi⁻ square sheets and 2D LiBi layers with La³⁺ ions as spacers. Band calculations indicate that both compounds are metallic.     

Sm2NiSn4: The intermediate structure type between ZrSi2 and CeNiSi2

A new rare earth nickel stannide, Sm₂NiSn₄, has been prepared by reacting the pure elements at high temperature in welded tantalum tubes. Its crystal structure was established by single crystal X-ray diffraction studies. Sm₂NiSn₄ crystallizes in the orthorhombic space group Pnma (No. 62) with cell parameters of a=16.878(2) Å, b=4.4490(7) Å, c=8.915(1) Å, and Z=4. Its structure can be viewed as the intermediate type between ZrSi₂ and CeNiSi₂. Sm₂NiSn₄ features two-dimensional (2D) corrugated [NiSn₄]⁶⁻ layers in which the 1D Sn zigzag chains and the 2D Sn square sheets are bridged by Ni atoms. The Sm³⁺ cations are located at the interlayer space. Results of both resistivity measurements and extended-Hückel tight-binding band structure calculations indicate that Sm₂NiSn₄ is metallic.     

Yb3Cu6Sn5, Yb5Cu11Sn8 and Yb3Cu8Sn4: crystal structure of three ordered compounds

Yb₃Cu₆Sn₅, Yb₅Cu₁₁Sn₈ and Yb₃Cu₈Sn₄ compounds were prepared in sealed Ta crucibles by induction melting and subsequent annealing. The crystal structures of Yb₃Cu₆Sn₅ and Yb₅Cu₁₁Sn₈ were determined from single crystal diffractometer data: Yb₃Cu₆Sn₅, isotypic with Dy₃Co₆Sn₅, orthorhombic, Immm, oI28, a=4.365(1) Å, b=9.834(3) Å, c=12.827(3) Å, Z=2, R=0.019, 490 independent reflections, 28 parameters; Yb₅Cu₁₁Sn₈ with its own structure, orthorhombic, Pmmn, oP48, a=4.4267(6) Å, b=22.657(8) Å, c=9.321(4) Å, Z=2, R=0.047, 1553 independent reflections, 78 parameters. Both compounds belong to the BaAl₄-derived defective structures, and are closely related to Ce₃Pd₆Sb₅ (oP28, Pmmn). The crystal structure of Yb₃Cu₈Sn₄, isotypic with Nd₃Co₈Sn₄, was refined from powder data by the Rietveld method: hexagonal, P6₃mc, hP30, a=9.080(1) Å, c=7.685(1) Å, Z=2, R_wp=0.040. It is an ordered substitution derivative of the BaLi₄ type (hP30, P6₃/mmc). All compounds show strong Cu-Sn bonds with a length reaching 2.553(3) Å in Yb₅Cu₁₁Sn₈.     

Synthesis and crystal structure of EuBi2

The new hypervalent binary phase EuBi₂ was obtained from high temperature solid-state reactions of the pure metal elements in welded Ta tubes under argon atmosphere. Its structure was established by single-crystal X-ray diffraction. The title compound crystallizes in the tetragonal space group I4₁/amd (No. 141) with cell parameters of , and Z=8. The structure of EuBi₂ is isotypic with HfGa₂ and features 1D Bi⁻ zigzag anionic chains along both a- and b-axes and 2D Bi⁻ square sheets normal to c-axis. It can be formulated as Eu²⁺(Bi)_chain⁻(Bi)_square⁻.     

Synthesis and structural characterization of A3In2Ge4 and A5In3Ge6 (A=Ca, Sr, Eu, Yb)—New intermetallic compounds with complex structures, exhibiting Ge-Ge and In-In bonding

Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr_1-xCa_x)₅In₃Ge₆ and (Eu_1-xYb_x)₅In₃Ge₆ (x≈0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) Å, b=4.4089(9)-4.4703(12) Å, and c=23.316(5)-23.557(6) Å. (Sr_1-xCa_x)₃In₂Ge₄ and (Sr_1-xYb_x)₃In₂Ge₄ (x≈0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) Å, b=4.5287(5)-4.5664(5) Å, c=10.3295(12)-10.3447(10) Å, and β=98.214(2)-98.470(2)°, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe₄ corner-shared tetrahedra. The A₅In₃Ge₆ structure (A=Sr/Ca or Sr/Yb) also features Ge₄ tetramers, and isolated In atoms in nearly square-planar environment, while the A₃In₂Ge₄ structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations.     

Syntheses, crystal and electronic structures of three new potassium cadmium(II)/zinc(II) tellurides: K2Cd2Te3, K6CdTe4 and K2ZnTe2

Three new ternary potassium(I) zinc(II) or cadmium(II) tellurides, namely, K₂Cd₂Te₃, K₆CdTe₄ and K₂ZnTe₂, were synthesized by solid-state reactions of the mixture of pure elements of K, Cd (or Zn) and Te in Nb tubes at high temperature. K₂Cd₂Te₃ belongs to a new structure type and its structure contains a novel two-dimensional [Cd₂Te₃]²⁻ layers perpendicular to the b-axis. K(5) cation is located at the center of five member rings of the 2D [Cd₂Te₃]²⁻ layer, whereas other K⁺ cations occupy the interlayer space. K₆CdTe₄ with a K₆HgS₄ type structure features a “zero-dimensional” structure composed of isolated CdTe₄ tetrahedra separated by the K⁺ ions. K₂ZnTe₂ in the K₂ZnO₂ structural type displays 1D [ZnTe₂]²⁻ anionic chains of edge sharing [ZnTe₄] tetrahedra separated by the potassium(I) ions. K₂Cd₂Te₃, K₆CdTe₄ and K₂ZnTe₂ revealed a band gap of 1.93, 2.51 and 3.0 eV, respectively.     

New open-framework in the uranyl vanadates A3(UO2)7(VO4)5O (A=Li, Ag) with intergrowth structure between A(UO2)4(VO4)3 and A2(UO2)3(VO4)2O

New uranyl vanadates A₃(UO₂)₇(VO₄)₅O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for _∞²[UO₂(VO₄)₂]⁴⁻ and D for _∞²[(UO₂)₂(VO₄)₃]⁵⁻ built from UO₆ square bipyramids and connected through VO₄ tetrahedra to _∞¹[U(3)O₅-U(4)O₅]⁸⁻ infinite chains of edge-shared U(3)O₇ and U(4)O₇ pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar _∞[UO₅]⁴⁻ chains are connected only by S-type sheets in A₂(UO₂)₃(VO₄)₂O and by D-type sheets in A(UO₂)₄(VO₄)₃, thus A₃(UO₂)₇(VO₄)₅O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoKα, λ=0.71073 Å, tetragonal symmetry, space group P4¯m2, Z=1, full-matrix least-squares refinement on the basis of F²; 1,a=7.2794(9) Å, c=14.514(4) Å, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I?2σ(I); 3, a=7.2373(3) Å, c=14.7973(15) Å, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I?2σ(I).     

Solid-state syntheses, crystal structures and properties of two novel metal sulfur chlorides—Zn6S5Cl2 and Hg3ZnS2Cl4

Two novel metal sulfur chlorides - Zn₆S₅Cl₂ (1) and Hg₃ZnS₂Cl₄ (2) - were obtained by solid-state reactions and structurally characterized by single-crystal X-ray diffraction. Compound 1 is characteristic of a 1-D tunnel-like structure, which connects to each other to construct a 3-D framework with the chlorine atoms locating at the voids. Compound 2 crystallizes in the acentric space group P6₃mc of the hexagonal system. Compound 2 features a 2-D layered motif, which is composed by the interconnected 12-membered Hg₆S₃Cl₃ rings with chair-like conformation. There are ZnSCl₃ tetrahedra located between the layers, yielding a sandwich-like structure. TG-DTA measurement shows that compound 1 is thermally stable up to 220 °C. Optical absorption spectra reveal the presence of sharp optical gap of 2.71 and 2.65 eV for 1 and 2, respectively.     

Syntheses, crystal structures and optical properties of the first strontium selenium(IV) and tellurium(IV) oxychlorides: Sr3(SeO3)(Se2O5)Cl2 and Sr4(Te3O8)Cl4

Two new quaternary strontium selenium(IV) and tellurium(IV) oxychlorides, namely, Sr₃(SeO₃)(Se₂O₅)Cl₂ and Sr₄(Te₃O₈)Cl₄, have been prepared by solid-state reaction. Sr₃(SeO₃)(Se₂O₅)Cl₂ features a three-dimensional (3D) network structure constructed from strontium(II) interconnected by Cl⁻, SeO₃²⁻ as well as Se₂O₅²⁻ anions. The structure of Sr₄(Te₃O₈)Cl₄ features a 3D network in which the strontium tellurium oxide slabs are interconnected by bridging Cl⁻ anions. The diffuse reflectance spectrum measurements and results of the electronic band structure calculations indicate that both compounds are wide band-gap semiconductors.     

A novel open-framework with non-crossing channels in the uranyl vanadates A(UO2)4(VO4)3 (A=Li, Na)

A new sodium uranyl vanadate Na(UO₂)₄(VO₄)₃ has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. It crystallizes in the tetragonal symmetry with space group I4₁/amd and following cell parameters: a=7.2267(4) Å and c=34.079(4) Å, V=1779.8(2) Å³, Z=4 with ρ_mes=5.36(3) g/cm³ and ρ_cal=5.40(2) g/cm³. A full-matrix least-squares refinement on the basis of F² yielded R₁=0.028 and wR₂=0.056 for 52 parameters with 474 independent reflections with I?2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector. The crystal structure is characterized by _∞²[(UO₂)₂(VO₄)] sheets parallel to (001) formed by corner-shared UO₆ distorted octahedra and V(2)O₄ tetrahedra, connected by V(1)O₄ tetrahedra to _∞¹[UO₅]⁴⁻ chains of edge-shared UO₇ pentagonal bipyramids alternately parallel to the a- and b-axis. The resulting three-dimensional framework creates mono-dimensional channels running down the a- and b-axis formed by face-shared oxygen octahedra half occupied by Na. The powder of Li analog compound Li(UO₂)₄(VO₄)₃ has been synthesized by solid-state reaction. The two compounds exhibit high mobility of the alkaline ions within the two-dimensional network of non-intersecting channels.     

One-dimensional chains in uranyl tungstates: Syntheses and structures of A8[(UO2)4(WO4)4(WO5)2] (A=Rb, Cs) and Rb6[(UO2)2O(WO4)4]

Three new uranyl tungstates, A₈[(UO₂)₄(WO₄)₄(WO₅)₂] (A=Rb (1), Cs (2)), and Rb₆[(UO₂)₂O(WO₄)₄] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to R₁=0.050, 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P2₁/n, (1): a=11.100(7), b=13.161(9), , β=90.033(13)°, , Z=8 and (2): , , , β=89.988(2)°, , Z=8. There are four symmetrically independent U⁶⁺ sites that form linear uranyl [O=U=O]²⁺ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO₅), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO₂)₄(WO₄)₄(WO₅)₂]⁴⁻ chains, consisting of WU₄O₂₅ pentamers linked by WO₄ tetrahedra and WO₅ square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (0 1 0). The A⁺ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W⁶⁺ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯ a=10.188(2), b=13.110(2), , α=97.853(3), β=96.573(3), γ=103.894(3)°, , Z=4. There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO₂²⁺, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO₂)₂O(WO₄)₄]⁶⁻ composed of UO₇ pentagonal bipyramids and W polyhedra. The chains involve dimers of UO₇ pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO₄ tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (1 1 1). The Rb⁺ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb₆[(UO₂)₂O(MoO₄)₄]. However, the compounds are not isostructural. Due to the tendency of the W⁶⁺ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO₅ configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type.     

Synthesis and structure of ternary transition-metal silicides Zr3Mn4Si6 and Hf3Mn4Si6

The isostructural ternary transition-metal silicides Zr₃Mn₄Si₆ and Hf₃Mn₄Si₆ can be prepared by direct reaction of the elemental components or by arc-melting. The single-crystal structure of Zr₃Mn₄Si₆ was determined by X-ray diffraction (Pearson symbol tP104, tetragonal, space group P4₂/mbc, Z=8, , ). Zr₃Mn₄Si₆ is isostructural to Nb₃Fe₃CrSi₆ and contains an essentially ordered arrangement of the transition-metal atoms. Square antiprismatic clusters with Zr and Mn atoms at the corners and Si atoms at the center share opposite faces to form one-dimensional columns extending along the c direction. These columns occupy channels that are outlined by a framework of edge- and face-sharing MnSi₆ octahedra. The extensive metal-metal interactions in the structure are complemented by Si-Si bonding in the form of dumbbells, linear chains, and zigzag chains.     

A new uranyl niobate sheet in the cesium uranyl niobate Cs9[(UO2)8O4(NbO5)(Nb2O8)2]

A new cesium uranyl niobate, Cs₉[(UO₂)₈O₄(NbO₅)(Nb₂O₈)₂] or Cs₉U₈Nb₅O₄₁ has been synthesized by high-temperature solid-state reaction, using a mixture of U₃O₈, Cs₂CO₃ and Nb₂O₅. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) Å, b=14.933(2) Å, c=20.155(2) Å β=110.59(1)°, P2₁/c space group and Z=4. The crystal structure was refined to agreement factors R₁=0.049 and wR₂=0.089, calculated for 4660 unique observed reflections with I?2σ(I), collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector.In this structure the UO₇ uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb₂O₈ entities and NbO₅ square pyramids, respectively, to form infinite uranyl niobate sheets stacking along the [010] direction. The Nb₂O₈ entities result from two edge-shared NbO₅ square pyramids. The Cs⁺ cations are localized between layers and ensured the cohesion of the structure.The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs⁺ cations to the infinite uranyl niobate layers and by the high density of these cations in the interlayer space without vacant site.Infrared spectroscopy investigated at room temperature in the frequency range 400-4000 cm⁻¹, showed some characteristic bands of uranyl ion and niobium polyhedra.     

Syntheses, crystal and electronic structures of two new lead indium phosphates: Pb2In4P6O23 and Pb2InP3O11

Two compounds Pb₂In₄P₆O₂₃ and Pb₂InP₃O₁₁ in the new family of lead indium phosphates were synthesized by high temperature solution growth (HTSG) method and structurally characterized by X-ray single crystal diffraction, powder diffraction and electron microscopy. Two title compounds display different types of 3D architectures with interesting tunnel structure are built up of the InO₆ octahedra and PO₄ tetrahedra, sharing the corners or edges, and the Pb²⁺ cations are sitting in the tunnel. The structure of Pb₂In₄P₆O₂₃ features a novel 3D open framework which can be considered as built from the layer of {In₄(P₂O₇)(PO₄)₂}²⁻ parallel to the ac plane interconnected by bridging the single PO₄. The structure of Pb₂InP₃O₁₁ can be described by the assemblage of [InP₂O₁₁] units with monophosphate groups. The stereochemical activity of the Pb^II lone pair has also been discussed. The electronic band structure calculations for the two compounds have also been performed with the density functional theory method. The study of calculations and optical diffuse reflectance absorption spectrum measurement show both compounds are indirect band-gap insulators.     

cis-trans Germanium chains in the intermetallic compounds ALi1-xInxGe2 and A2(Li1-xInx)2Ge3 (A=Sr, Ba, Eu)—experimental and theoreticalstudies

Two types of strontium-, barium- and europium-containing germanides have been synthesized using high temperature reactions and characterized by single-crystal X-ray diffraction. All reported compounds also contain mixed-occupied Li and In atoms, resulting in quaternary phases with narrow homogeneity ranges. The first type comprises EuLi_0.91(1)In_0.09Ge₂, SrLi_0.95(1)In_0.05Ge₂ and BaLi_0.99(1)In_0.01Ge₂, which crystallize in the orthorhombic space group Pnma (BaLi_0.9Mg_0.1Si₂ structure type, Pearson code oP16). The lattice parameters are a=7.129(4)-7.405(4) Å; b=4.426(3)-4.638(2) Å; and c=11.462(7)-11.872(6) Å. The second type includes Eu₂Li_1.36(1)In_0.64Ge₃ and Sr₂Li_1.45(1)In_0.55Ge₃, which adopt the orthorhombic space group Cmcm (Ce₂Li₂Ge₃ structure type, Pearson code oC28) with lattice parameters a=4.534(2)-4.618(2) Å; b=19.347(8)-19.685(9) Å; and c=7.164(3)-7.260(3) Å. The polyanionic sub-structures in both cases feature one-dimensional Ge chains with alternating Ge-Ge bonds in cis- and trans-conformation. Theoretical studies using the tight-binding linear muffin-tin orbital (LMTO) method provide the rationale for optimizing the overall bonding by diminishing the π-p delocalization along the Ge chains, accounting for the experimentally confirmed substitution of Li forIn.     

Syntheses, structures, optical properties, and theoretical calculations of Cs2Bi2ZnS5, Cs2Bi2CdS5, and Cs2Bi2MnS5

Three new compounds, Cs₂Bi₂ZnS₅, Cs₂Bi₂CdS₅, and Cs₂Bi₂MnS₅, have been synthesized from the respective elements and a reactive flux Cs₂S₃ at 973 K. The compounds are isostructural and crystallize in a new structure type in space group Pnma of the orthorhombic system with four formula units in cells of dimensions at 153 K of a=15.763(3), b=4.0965(9), c=18.197(4) Å, V=1175.0(4) Å³ for Cs₂Bi₂ZnS₅; a=15.817(2), b=4.1782(6), c=18.473(3)  Å, V=1220.8(3)  ų for Cs₂Bi₂CdS₅; and a=15.830(2), b=4.1515(5), c=18.372(2) Å, V=1207.4(2) Å³ for Cs₂Bi₂MnS₅. The structure is composed of two-dimensional _∞²[Bi₂MS₅²⁻] (M=Zn, Cd, Mn) layers that stack perpendicular to the [100] axis and are separated by Cs⁺ cations. The layers consist of edge-sharing _∞¹[Bi₂S₆⁶⁻] and _∞¹[MS₃⁴⁻] chains built from BiS₆ octahedral and MS₄ tetrahedral units. Two crystallographically unique Cs atoms are coordinated to S atoms in octahedral and monocapped trigonal prismatic environments. The structure of Cs₂Bi₂MS₅, is related to that of Na₂ZrCu₂S₄ and those of the AMM′Q₃ materials (A=alkali metal, M=rare-earth or Group 4 element, M′= Group 11 or 12 element, Q=chalcogen). First-principles theoretical calculations indicate that Cs₂Bi₂ZnS₅ and Cs₂Bi₂CdS₅ are semiconductors with indirect band gaps of 1.85 and 1.75 eV, respectively. The experimental band gap for Cs₂Bi₂CdS₅ is ≈1.7 eV, as derived from its optical absorption spectrum.     

Syntheses and structures of three new scandium selenites: Sc2(SeO3)3·H2O, Sc2 (SeO3)3·3H2O and CsSc3(SeO3)4 (HSeO3)2·2H2O

Three new hydrated scandium selenites have been hydrothermally synthesized as single crystals and structurally and physically characterized. Sc₂(SeO₃)₃·H₂O crystallizes as a new structure type containing novel ScO₇ pentagonal bipyramidal and ScO₆₊₁ capped octahedral coordination polyhedra. Sc₂(SeO₃)₃·3H₂O contains typical ScO₆ octahedra and is isostructural with its M₂(SeO₃)₃·3H₂O (M=Al, Cr, Fe, Ga) congeners. CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O contains near-regular ScO₆ octahedra and has essentially the same structure as its indium-containing analogue. All three phases contain the expected pyramidal [SeO₃]^2- selenite groups. Crystal data: Sc₂(SeO₃)₃·3H₂O, M_r=524.85, trigonal, R3c (No. 161), , , , Z=6, R(F)=0.018, wR(F²)=0.036; Sc₂(SeO₃)₃·H₂O, M_r=488.82, orthorhombic, P2₁2₁2₁ (No. 19), , , , , Z=4, R(F)=0.051, wR(F²)=0.086; CsSc₃(SeO₃)₄(HSeO₃)₂·2H₂O, M_r=1067.60, orthorhombic, Pnma (No. 62), , , , , Z=4, R(F)=0.035, wR(F²)=0.070.     

[Ni(C6N2H14)2][Zn4(H2O)(HPO3)5]: A new open-framework zinc phosphite with intersecting 8-, 12- and 16-ring channels

A new three-dimensional (3-D) zinc phosphite with Zn/P ratio of 4/5, [Ni(C₆N₂H₁₄)₂][Zn₄(H₂O)(HPO₃)₅] (1), has been prepared by using self-assembled nickel complexes as the structure-directing agents. Its structure is built up from strict alternation of ZnO₄ tetrahedra and HPO₃ pseudo-pyramids, resulting in an open framework with multi-directional intersecting 8-, 12- and 16-ring channels. The unique nickel complexes Ni(DACH)₂ (DACH=1,2-diaminocyclohexane) only involving the cis-DACH acting as ligands are self-assembled under hydrothermal conditions, and act as the structure-directing agents (SDAs) to direct the formation of compound 1. Nickel complexes reside in the channels in a manner that the hydrophobic ends of the cis-DACH molecules exclusively protrude into the 16-ring pores and the amino groups closely interact with the charged inorganic framework through weak H-bonds. The interesting arrangements of nickel complexes imply a feasible approach to the design and synthesis of extra-large pore materials.