The Crystal Structures and Raman Spectra of Three New Hydrothermally Synthesized Copper-Zinc-Oxotellurates(IV)

Three new copper-zinc-tellurites, Zn4Cu((TeO3)-O-IV)(4)Cl-2, Cu2Zn2((TeO3)-O-IV)(2)(SO4)(OH)(2)center dot H2O and Cu2Zn((TeO4)-O-IV)(SO4)center dot H2O (henceforth I, II and III), were synthesized under mild hydrothermal conditions (473 K, in Teflon-lined steel vessels). They were characterized in detail by a combination of crystal-structure determination (using single-crystal X-ray diffraction data), single-crystal micro-Raman spectroscopy and chemical analyses (energy-dispersive X-ray spectroscopy in a scanning electron microscope). Each compound crystallizes in a new structure type, and additionally, II and III represent the first two ever reported copper-zinc-tellurite-sulfates. I [systematic name: tetrazinc copper(II) tetrakis-oxotellurate(IV) dichloride] is triclinic, P1, and forms a framework structure based on ZnO6 and ZnO5Cl octahedra, linked into sheets connected via Jahn-Teller-distorted CuO4Cl2 octahedra, with (TeO3)-O-IV trigonal pyramids and (Te2O6)-O-IV dimers (composed of two edge-sharing (TeO4)-O-IV disphenoids) filling the remaining space. II [dicopper(II) dizinc bis-oxotellurate(IV) oxosulfate(VI) bis-hydroxide monohydrate] is trigonal, R3m, with a simonkolleite-like framework. Distinct layers formed from (Cu,Zn)phi(6) (phi = O, OH) octahedra and (TeO3)-O-IV trigonal pyramids extend parallel to (001) and sandwich disordered SO42- anions and H2O groups. III [dicopper(II) zinc oxotellurate(IV) oxosulfate(VI) hydrate] is orthorhombic, Pnma, and also has a layered structure [extending parallel to (100)]. Positively charged layers of composition [(Cu2ZnTeO4)-O-IV](2+) (containing Te as (TeO4)-O-IV disphenoids) alternate with SO42- anions and H2O groups in the interlayer space. Stacking disorder caused by the order-disorder nature of the crystal structure is reflected by the presence of residual electron density in difference-Fourier maps and the structure was refined as an overlay of two stacking possibilities.