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Abstract: The three new framework Rb uranyl phosphates and arsenates with anionic parts based on different type of polymeric anions have been prepared by high-temperature solid-state reactions: Rb4[(UO2)6(P2O7)4(H2O)] (1), Rb2[(UO2)3(P2O7)(P4O12)] (2), Rb[(UO2)2(As3O10)] (3). The crystal structures of the synthesized compounds have been solved by direct methods: 1—monoclinic P21/c, a=9.672(1)Å, b=12.951(1)Å, c=32.231(3)Å, β=90.116(4)°, V=4037.3(6)Å3, Z=4, R 1=0.0926 for 6351 unique reflections with ; 2—monoclinic, P21/c, a=6.791(1)Å, b=16.155(3)Å, c=19.856(4)Å, β=97.48(5)°, V=2159.8(7)Å3, Z=4, R 1=0.0286 for 3617 unique reflections with ; 3—orthorhombic, Pbcn, a=10.558(1)Å, b=11.037(1)Å, c=11.464(1)Å, V=1335.9(2)Å3, Z=4, R 1=0.0489 for 1384 unique reflections with . The structures of title are compounds based on 3D negatively charged frameworks with chemical compositions [(UO2)6(P2O7)4(H2O)]4− in 1, [(UO2)3(P2O7)(P4O12)]2− in 2 and [(UO2)2(As3O10)]− in 3. These negative charges are compensated by rubidium cations which are in the channels of 1 and closed cages in structures of 2 and 3. The channels in 1 are directed along the a direction and have minimum dimensions ∼5Å×6Å. This is the first example of porosity generation through solid state synthesis in uranyl compounds. For the first time in uranium chemistry polymeric anionic groups P4O12 and As3O10 were observed in structure of 2 and 3. [Copyright &y& Elsevier]

Abstract: Four new Li uranyl phosphates and arsenates have been prepared by high-temperature solid-state reactions: α-Li[(UO2)(PO4)] (1), α-Li[(UO2)(AsO4)] (2), β-Li[(UO2)(AsO4)] (3) and Li2[(UO2)3(P2O7)2] (4). The structures of the compounds have been solved by direct methods: 1—triclinic, , a=5.0271(1)Å, b=9.8799(2)Å, c=10.8920(2)Å, α=108.282(9)°, β=102.993(8)°, γ=104.13(1)°, V=470.69(2)Å3, Z=4, R 1=0.0415 for 2786 unique reflections with |F 0|⩾4σF ; 2—triclinic, , a=5.129(2)Å, b=10.105(3)Å, c=11.080(3)Å, α=107.70(2)°, β=102.53(3)°, γ=104.74(3)°, V=501.4(3)Å3, Z=4, R 1=0.055 for 1431 unique reflections with |F 0|⩾4σ F; 3—triclinic, , a=5.051(1)Å, b=5.303(1)Å, c=10.101(1)Å, α=90.31(1)°, β=97.49(1)°, γ=105.08(1)°, V=258.80(8)Å3, Z=2, R 1=0.0339 for 2055 unique reflections with |F 0|⩾4σ F; 4—triclinic, , a=5.312(1)Å, b=6.696(1)Å, c=12.542(1)Å, α=94.532(9)°, β=99.059(8)°, γ=110.189(7)°, V=409.17(10)Å3, Z=2, R 1=0.0565 for 1355 unique reflections with |F 0|⩾4σ F. The structures of all four compounds are based upon 3-D frameworks of U and T polyhedra (T=P, As). Phases 1 and 2 are isostructural and consist of U2O12 dimers and UO6 square bipyramids linked by single TO4 tetrahedra. The structure of 3 consists of 3-D framework of corner-sharing UO6 bipyramids and AsO4 tetrahedra. In the structure of 4, the framework is composed of U2O12 dimers, UO6 bipyramids and P2O7 dimers. In all the compounds, Li+ cations reside in framework cavities. The topologies of the 3-D frameworks can be described as derivatives of the PtS (cooperite) network. [Copyright &y& Elsevier]

Abstract: Three new uranyl tungstates, A 8[(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 , 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P21/n, (1): , , , , , and (2): , , , , , . 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 (010). 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¯, , , , , , , . There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO2 2+, 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 (111). 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. [Copyright &y& Elsevier]

Two new mixed organic–inorganic uranyl molybdates, (C6H14N2)3[(UO2)5(MoO4)8](H2O)4 (1) and (C2H10N2)[(UO2)(MoO4)2] (2), have been obtained by hydrothermal methods. The structure of 1 [triclinic, P1¯, Z=1, a=11.8557(9), b=11.8702(9), c=12.6746(9) A˚, α=96.734(2)°, β=91.107(2)°, γ=110.193(2)°, V=1659.1(2) A˚] has been solved by direct methods and refined on the basis of F2 for all unique reflections to R1=0.058, which was calculated for the 5642 unique observed reflections (|Fo|⩾4σF). The structure contains topologically novel sheets of uranyl square bipyramids, uranyl pentagonal bipyramids, and MoO4 tetrahedra, with composition [(UO2)5(MoO4)8]6−, that are parallel to (−101). H2O groups and 1,4-diazabicyclo [2.2.2]-octane (DABCO) molecules are located in the interlayer, where they provide linkage of the sheets. The structure of 2 [triclinic, P1¯, Z=2, a=8.4004(4), b=11.2600(5), c=13.1239(6) A˚, α=86.112(1)°, β=86.434(1)°, γ=76.544(1)°, V=1203.14(10) A˚] has been solved by direct methods and refined on the basis of F2 for all unique reflections to R1=0.043, which was calculated for 5491 unique observed reflections (|Fo|⩾4σF). The structure contains topologically novel sheets of uranyl pentagonal bipyramids and MoO4 tetrahedra, with composition [(UO2)(MoO4)2]2−, that are parallel to (110). Ethylenediamine molecules are located in the interlayer, where they provide linkage of the sheets. All known topologies of uranyl molybdate sheets of corner-sharing U and Mo polyhedra can be described by their nodal representations (representations as graphs in which U and Mo polyhedra are given as black and white vertices, respectively). Each topology can be derived from a simple black-and-white graph of six-connected black vertices and three-connected white vertices by deleting some of its segments and white vertices. [Copyright &y& Elsevier]

Five Rb uranyl molybdates have been prepared by solid-state reactions and hydrothermal syntheses. The structure of each compound has been investigated using single-crystal X-ray diffraction data collected using MoKα radiation and a Charge-Coupled-device-based area detector. The structure of Rb6[(UO2)(MoO4)4] (monoclinic, C2/c, Z=4,a=17.312(1) A˚, b=11.5285(8) A˚, c=13.916(1) A˚, β=127.634(1)°, V=2199.4(3) A˚3, R1=0.029) is based on finite clusters of composition [(UO2)(MoO4)4]6− composed of a UrO4 (Ur: UO22+ uranyl ion) tetragonal bipyramid that shares each equatorial vertex with an adjacent MoO4 tetrahedron. The structure of Rb6[(UO2)2O(MoO4)4] (triclinic, P-1, Z=2, a=10.1567(5) A˚, b=10.1816(5) A˚, c=13.1129(6) A˚, α=76.921(1)°, β=76.553(1)°, γ=65.243(1)°, V=1184.8(1) A˚3, R1=0.047) is based upon chains of composition [(UO2)2O(MoO4)4]6− containing UrO5 pentagonal bipyramids and MoO4 tetrahedra. The structure of Rb2[(UO2)(MoO4)2] (monoclinic, P21/c, Z=8, a=12.302(1) A˚, b=13.638(1) A˚, c=13.508(1) A˚, β=94.975(2)°, V=2257.8(4) A˚3, R1=0.059) contains sheets of composition [(UO2)(MoO4)2]2− involving corner-sharing UrO5 pentagonal bipyramids and MoO4 tetrahedra. The structure of Rb2[(UO2)2(MoO4)3] (orthorhombic, Pna21, Z=4, a=20.214(1) A˚, b=8.3744(4) A˚, c=9.7464(5) A˚, V=1649.9(1) A˚3, R1=0.027) consists of a framework with composition [(UO2)2(MoO4)3]2− that involves corner-sharing UrO5 pentagonal bipyramids and MoO4 tetrahedra. The structure of Rb2[(UO2)6 (MoO4)7 (H2O)2] (orthorhombic, Pbcm, Z=4, a=13.961(2) A˚, b=10.7515(16) A˚, c=25.579(4) A˚, V=3839(1) A˚3, R1=0.037) consists of a framework of corner-sharing UrO5 pentagonal bipyramids, UrO4(H2O) pentagonal bipyramids and MoO4 tetrahedra. These structures are compared to those of other uranyl molybdates. The structural diversity and variability of uranyl molybdates is related to the high degree of flexibility of the U–O–Mo linkages. [Copyright &y& Elsevier]

Abstract: Single crystals of Cs2(UO2)(CrO4)2 and Rb2(UO2)(CrO4)2 were prepared by solid state reactions. The structures are based upon the [(UO2)(CrO4)2]2− chains. Within the chains, UrO5 pentagonal bipyramids (Ur=uranyl) form Ur 2O8 dimers, which are linked via CrO4 tetrahedra into one-dimensional chains. The CrO4 tetrahedra coordinate uranyl ions in both mono- and bidentate fashion, which is unusual for uranyl chromates. The bidentate coordination has a strong influence upon geometrical parameters of both U and Cr coordination polyhedra. The conformation of the chains in 1 and 2 is different due to the different size of the Cs+ and Rb+ cations. [Copyright &y& Elsevier]

Abstract: Crystal growth experiments yielded single crystals of Sr4Ga2O7. The title compound is monoclinic, space group P1c1, , , , , , ( for 7155 observed reflections and 660 parameters). The crystals showed twinning by pseudo-merohedry. Furthermore, the diffraction data exhibited the typical features of a superstructure. Sr4Ga2O7 can be classified as a mixed anion gallate comprising insular [GaO4]-groups and [Ga3O10]-trimers. Both anion groups are located in layers perpendicular to [100]. 32 symmetrically independent Sr-cations crosslink between the tetrahedral anion groups. Alternatively, the compound can be described as a 3×4×4 superstructure of ABO3 perovskite, with 22.2% vacancies in the oxygen sublattice. The relationship with perovskite can be expressed in the following crystal chemical formula: Sr(Ga2/3Sr1/3)(O7/9□2/9)3. A discussion of the structure in the context with other similar defect perovskites in presented. [Copyright &y& Elsevier]

K[AsW2O9], prepared by high-temperature solid-state reaction, is the first member of the arsenate–tungsten bronze family. The structure of K[AsW2O9] is based on a 3-dimensional (3D) oxotungstate–arsenate framework with the non-centrosymmetric P212121 space group, a=4.9747(3)Å, b=9.1780(8) Å, c=16.681(2) Å. The material was characterized using X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Raman and infrared (IR) spectroscopic techniques. The results of DSC demonstrate that this phase is stable up to 1076K. Second harmonic generation (SHG) measurements performed on a powder sample demonstrate noticeable (0.1 of LiIO3) non-linear optical (NLO) activity. [ABSTRACT FROM AUTHOR]

Abstract: Two new bismuth phosphate halides [Bi8O8][BiO2](PO4)2Cl and [Bi8O8][BiO2](PO4)2Br, high-temperature phases have been obtained by the solid-state reaction method. Oa–Bi bonds (Oa—additional oxygen atoms not bonded to P) are the shortest and therefore the strongest in the studied structures, which makes it reasonable to consider the Bi–O substructure consisting of OBi4 tetrahedra and OBi3 triangles as an independent structural unit interacting with X atoms and PO4 tetrahedra through relatively weak Bi–X and Bi–O bonds. The topology of this oxocentered Bi–O structural unit is two-dimensional and obviously related to the [O2Bi2]2+ layer typical for the Aurivillius type compounds. The formula of the oxocentered block is ([O8Bi8][O2Bi])7+ with the first part in square brackets designating the moiety formed by the OBi4 tetrahedra, whereas the second part shows 3-coordinated O atoms and the Bi atoms not participating in the OBi4 tetrahedra. The interlayer in between the oxocentered 2D blocks is occupied by the phosphate groups and halogen atoms which are organized in alternating stripes. In the case of studied bismuth oxyphosphate halides as well as in other previously reported compounds, ‘additional’ oxygen atoms can be considered as segregation centers for Bi3+ cations. This viewpoint may appear to be useful for design of new schemes and synthetic routes to the bismuth oxysalt compounds with different structural architectures and possible useful applications. The comparison with the similar stairs-like layers in bismuth oxysalt structures is also given. [Copyright &y& Elsevier]