Synthesis and characterization of two novel mixed metal tellurates: KGaTeO5·H2O and K3GaTe2O8(OH)2·H2O

Ca10Na10[Te9O42](H2O): a hydrothermally synthesized quaternary tellurium(vi) oxide containing edge-sharing octahedral trimers

A new tellurium(vi) oxycompound, Ca10Na10[Te9O42](H2O), was synthesized by a high-temperature, high-pressure hydrothermal reaction at 550 °C, its structure determined by single-crystal X-ray diffraction, and further characterized by energy dispersive, infrared, and X-ray photoelectron spectroscopy. The compound crystallizes in the centrosymmetric trigonal space group R3[combining macron]c (no. 167) with a = 9.743(2), c = 66.337(13) Å, and Z = 6. The structure consists of discrete linear edge-sharing octahedral trimers with the composition Te3O1410-, which is a new type of finite Te-O oligomer with Te6+ only. The large complex anions form a hexagonal close-packed lattice with the octahedral and tetrahedral interstices being filled with Ca2+ and Na+ cations and water molecules. The octahedral trimers in every other h.c.p. layer rotate around the 31 screw axis for 120°; therefore the unit cell has a very long c axis. This work is one of the few examples of the synthesis of metal tellurates by supercritical hydrothermal techniques.

Explorations of new phases in the Ga(III)/In(III)-Cu(II)-Se(IV)-O system

Four new gallium(III)/indium(III), copper(II), selenium(IV) oxides, namely, Ga(2)Cu(SeO(3))(4) (1), Ga(2)CuO(SeO(3))(3) (2), and M(2)Cu(3)(SeO(3))(6) (M = Ga 3, In 4), have been synthesized by hydrothermal or high-temperature solid-state reactions. The structure of Ga(2)Cu(SeO(3))(4) (1) features a 2D layer of corner-sharing GaO(6) and CuO(6) octahedra with the SeO(3) groups hanging on both sides of the 2D layer. Ga(2)CuO(SeO(3))(3) (2) features a pillared layered structure in which the 1D Cu(SeO(3))(3)(4-) chains act as the pillars between 2D layers formed by corner- and edge-sharing GaO(n) (n = 4, 5) polyhedra. Although the chemical compositions of M(2)Cu(3)(SeO(3))(6) (M = Ga 3, In 4) are comparable, they belong to two different structural types. Ga(2)Cu(3)(SeO(3))(6) (3) exhibits a pillared layered structure built by [Ga(2)Cu(3)(SeO(3))(4)](4+) thick layers with Se(3)O(3)(2-) groups as pillars. The structure of In(2)Cu(3)(SeO(3))(6) (4) features a 3D network composed of [In(2)(SeO(3))(2)](2+) layers and [Cu(3)(SeO(3))(4)](2-) layers interconnected through Se-O-Cu and In-O-Cu bridges, exhibiting 8-MR helical tunnels along the a-axis. Results of magnetic property measurements indicate that there are considerable antiferromagnetic interactions between copper(II) centers in Ga(2)CuO(SeO(3))(3) (2) and M(2)Cu(3)(SeO(3))(6) (M = Ga 3, In 4). Interestingly, Ga(2)Cu(3)(SeO(3))(6) (3) behaves as a weak ferromagnet below the critical temperature of T(c) = 15 K. Further magnetic studies indicate that the compound is a canted antiferromagnet with a large canting angle of about 7.1 degrees.

Synthesis, structure, and characterization of novel two- and three-dimensional vanadates: Ba2.5(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O

Two new vanadates, Ba(2.5)(VO2)3(SeO3)4.H2O and La(VO2)3(TeO6).3H2O, have been synthesized by hydrothermal methods using BaCO3, Ba(OH)2.H2O, La(NO3)3.6H2O, V2O5, TeO2, and H2SeO3 as reagents. The structures were determined by single-crystal X-ray diffraction. Ba(2.5)(VO2)3(SeO3)4.H2O exhibits a two-dimensional layered structure consisting of VO(5) square pyramids and SeO3 polyhedra, whereas La(VO2)3(TeO6).3H2O has a three-dimensional framework structure composed of VO(4) tetrahedra and TeO6 octahedra. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis are also presented. Crystal data: Ba(2.5)(VO2)3(SeO3)4.H2O, trigonal, space group P (No. 147) with a = b = 12.8279(15) A, c = 7.2631(9) A, V = 1035.1(2) A(3), and Z = 2; La(VO2)3(TeO6).3H2O, trigonal, space group R3c (No. 161) with a = b = 9.4577(16) A, c = 23.455(7) A, V = 1816.9(7) A3, and Z = 6.

Structure and Properties of the Thorium Vanadyl Tellurate, Th(VO2)2(TeO6)(H2O)2

The hydrothermal reaction of Th(NO3)4.xH2O with V2O5 and H6TeO6 at 200 degrees C under autogenously generated pressure results in the formation of Th(VO2)2(TeO6)(H2O)2 as a pure phase. The single-crystal X-ray data indicate that Th(VO2)2(TeO6)(H2O)2 possesses a three-dimensional structure constructed from ThO9 tricapped trigonal prisms, VO5 distorted square pyramids, VO4 distorted tetrahedra, and TeO6 distorted octahedra. Both of the vanadium polyhedra contain VO2+ vanadyl units with two short V=O bond distances. The tellurate octahedron is tetragonally distorted and utilizes all of its oxygen atoms to bond to adjacent metal centers, sharing edges with ThO9 and VO5 units, and corners with two ThO9, one VO5, and two VO4 polyhedra. Crystallographic data: Th(VO2)2(TeO6)(H2O)2, orthorhombic, space group Pbca, a = 12.6921(7), b = 11.5593(7), c = 13.0950(8) A, Z = 8 (T = 193 K). The UV-vis diffuse reflectance spectrum of Th(VO2)2(TeO6)(H2O)2 shows vanadyl-based charge-transfer absorption features. Th(VO2)2(TeO6)(H2O)2 decomposes primarily to Th(VO3)4 when heated at 600 degrees C in air.