1,721,059 research outputs found
Cerium(IV) fluoride and fluoride-arsenate frameworks
No full textFive new cerium (IV) fluoride and fluoride–arsenate framework structures have been synthesised hydrothermally using CeF4 as a fluoride source. Cs[Ce2F8[F·H2O]] ( I) consists of layers, formed from linked Ce(F,O)n polyhedra cross-linked by hydrogen bonding that defines large channels containing the caesium ions. [(NH4)5(H2O)2][Ce4(AsO4)6(H2O)F3] ( II), has an open framework structure with large channels filled with NH4+ cations and H2O molecules. Ce[AsO4]F ( III) and Ce[AsO4]F[H2O] ( IV) exhibit two types of bridging (Ce–O–Ce and Ce–F–Ce) bonds between Ce(O,F)n polyhedra, and (NH4)[CeF2(AsO4)] ( V), is isostructural with the previously reported fluoride-phosphate (NH4)[CeIVF2(PO4
[NH4]12[(MoO2)2O(HPO4)2]4[PO4]X, X = Cl, Br—new porous layer molybdenophosphates with embedded multiple anionic and cationic guests
No full textThe compounds [NH4]12[(MoO2)2O(HPO4)2]4[PO4]X, X = Cl, Br are constructed from molybdenophosphate layers of unique topology that are penetrated by channels containing perfectly ordered, alternating ammonium cations and free orthophosphate (PO43-) or halide (Cl-, Br-) anion
A new host for MnO43-: synthesis and characterisation of the NaCaV1-xMnxO4 system
No full textThe incorporation of the intensely coloured charge transfer species MnO43- has been investigated for NaCaVO4. The series of compounds NaCaV1-xMnxO4 (where x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) has been successfully prepared and results in the formation of blue/green coloured powders. A structural characterisation of the materials has been performed and the results are presented. The series is seen to adopt an orthorhombic structure in the space group Cmcm (No.63). On increasing manganese content an overall reduction of the cell volume was observed and the limit of substitution occurs at x 0.08
Characterisation of four new two-dimensional lithium beryllofluoro-layered compounds
No full textFour new amine-templated materials, containing two-dimensional lithium beryllofluoride sheets of the stoichiometry [LiBeF4](-), have been synthesised under hydrothermal and ambient pressure conditions. [LiBeF4][C6H4(CH3)CH2NH3] (1), [LiBeF4] [C6H4CH2NH3Cl (2), [LiBeF4](2)- [NH3CH2CH2CH2NH3] (3), and [LiBeF4][C6H5CH2CH2CH2NH3] (4) all contain well-separated anionic sheets containing two different topologies with the 'inter-layer' regions comprising of organoamine templating species. Use of the different organoamine templating agents results in compounds possessing very different relative arrangements of the lithium beryllofluoride sheets. The materials crystallise in P-centred orthorhombic and monoclinic cells; for 1 (templating agent: 3-methylbenzylamine) Pca2(1); for 2 (4-chlorobenzylamine) Pbca; for 3 (1,3-diamminopropane) Pccn, and for 4 (3-phenyl-1-propylamine) P2(1)/c. Hydrogen bonding exists between ions situated on the protonated amine groups on the templating species and electronegative fluoride ions, on MF4 tetrahedra (where M = Li and Be)
Synthesis and crystal structures of iron hydrogen phosphates
No full textThree new iron hydrogen phosphate compositions have been synthesised under hydrothermal conditions; Fe(II)2O(HPO4) ( 1), (NH4)3Fe(III)3(HPO4)6 ( 2) and Fe1.34(III)(PO4)OH0.96 ( 3). 1 and 2 have framework structures constructed from FeO6 octahedra and HPO4/PO4 tetrahedra containing cavities; in the case of 2, these are occupied by ammonium cations while in 1 they are cross linked by hydrogen bonding involving the HPO4 groups. Crystals of 3 grow as 30 m octahedral jackstones and this synthetic material adopts the structure from the Lipscombite solid solution. Thermal decomposition of these materials yields simple iron phosphates and the potential of these compounds and their derivatives, formed for example through Li+-ion exchange of NH4+, for battery applications is discusse
Structural observation of photochromism
No full textThe reversible formation of a long-lived, coloured F-centre has been observed in small structural changes delineated by neutron diffraction
Synthesis and structure of new layered copper oxide iodides, Sr2CuO2I2 and Sr2Cu3O4I2
No full textThe first layered copper oxide iodides Sr2CuO2I2 and Sr2Cu3O4I2 have been synthesised by reaction of SrO, SrI2 and CuO in evacuated silica ampoules. Sr2CuO2I2 crystallises with a K2NiF4-type structure and contains infinite CuO2 planes separated by double SrI rocksalt layers. Sr2Cu3O4I2 contains sheets of Cu3O4 stoichiometry separated by fluorite Sr2I2 layers. Incorporation of the iodide ion results in an in-plane Cu–O bond distance of 2.015 Å in Sr2CuO2I2 whilst the two distinct copper sites in Sr2Cu3O4I2possess near identical in-plane Cu–O interactions ? 1.96 Å
New directions in synthetic and structural solid state chemistry: the legacy of high temperature superconductivity beyond cuprate chemistry
No full textThe synthetic and structural chemistry of copper in complex oxides has developed extremely rapidly since the first reports of high temperature superconductivity in 1986. This progress in cuprate solid state chemistry has far outpaced that in many other areas of complex oxide chemistry. Significant new developments have included the formation of new complex oxides incorporating the volatile post transition oxides of Tl, Hg, Pb and Bi, the generation of complex structures based on stacked perovskites and/or other building blocks, the use of very high pressures during synthesis and the stabilisation of complex anions in oxides. Many of these advances are now being developed outside cuprate chemistry particularly with other late first row transition metals such as iron, nickel and cobalt. The aim of this article is not to review cuprate chemistry but to demonstrate where work on high T-c superconductors has resulted in significant recent progress for other transitional metal oxide systems. The syntheses and structures of these new complex oxides are described and areas where developments, derived from the discoveries in cuprate chemistry, can be expected in the next decade are also proposed
Hydrothermal routes to new sodium polytungstates
No full textThe new acidic sodium polytungstates, Na5[H7W12O42]·20H2O ( 1) and Na2[H10W12O42]·20H2O ( 2), have been synthesised under hydrothermal conditions where variations of pH and temperature allow control of the protonation of the [W12O42]12- cluster in the products. The polytungstate cluster, [HnW12O42](12-n)-, in each compound consists of the well known polyhedral unit based on 12 edge- and corner-sharing WO6 octahedra, though the decoration of this unit with varying levels of protons results in significant changes in the W–O distances. The polytungstate clusters exist in arrays separated by sodium ions and water molecules forming well separated, (polytungstate centre to centre distance of 10.87 Å), rhombohedrally stacked units in 1 and strongly hydrogen bonded and more tightly packed units, (centre to centre distance of 9.34 Å), due to the high H : Na ratio in 2<br/
Synthesis and structure of cobalt (II) oxide halides—Sr2CoO2X2 (X = Cl, Br)
No full textThe first layered cobalt (II) oxide halides, Sr2CoO2Cl2 and Sr2CoO2Br2, have been synthesized and their structures determined from Rietveld refinement of powder X-ray data. The materials are structural analogues of the K2NiF4 cuprate phase Sr2CuO2Cl2, crystallizing in space group I4/mmm. The compounds contain CoO2 square planes separated by SrX layers (X=Cl,Br). The bromide material displays the expected increase in cell dimensions, i.e., for Sr2CoO2Cl2, a=4.06251(5) Å, c=15.1251(3) Å and for Sr2CoO2Br2, a=4.08891(7) Å, c=16.4077(4) Å
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