Synthesis and structure of A4V6[Te24+Te6+]O24 (A = K, Rb)—two new quaternary mixed-valent tellurium oxides

Abstract

Two new mixed-valent tellurium oxides with vanadium(V), A₄V₆[Te₂⁴⁺Te⁶⁺]O₂₄ (A = K and Rb), have been synthesized by hydrothermal and conventional solid state techniques. Their structures were determined by single-crystal X-ray diffraction analysis. These two iso-structural compounds exhibit layered structural topologies consisting of [V₆Te₃O₂₄]⁴⁻ anionic units. In these anionic structural units, a Te⁶⁺O₆ octahedron is connected to six VO₄ tetrahedra by corner-sharing to generate a [V₆TeO₂₄] unit, and each of these [V₆TeO₂₄] units are interconnected by sharing two Te⁴⁺O₃ polyhedra to complete the infinite [V₆Te₃O₂₄]⁴⁻ sheets. Infrared spectroscopy, UV-Visible diffuse reflectance spectroscopy, and thermogravimetric analysis were also performed on these two compounds. Crystal data: K₄V₆Te₃O₂₄, trigonal, space group Rc (No. 167) with a = b = 9.7075(6) Å, c = 42.701(3) Å, V = 3484.9(4) ų, and Z = 6; Rb₄V₆Te₃O₂₄, trigonal, space group Rc (No. 167) with a = b = 9.8399(9) Å, c = 43.012(4) Å, V = 3606.6(6) ų, and Z = 6.