K[(CuII,MnII,MnIII)2(TeO3)3]∙2H2O, the first zemannite-type structure based on a Jahn-Teller-distorted framework

Abstract Synthetic single crystals of K[(Cu II ,Mn III ) 2 (TeO 3 ]·2H O were obtained from an overconcentrated alkaline aqueous solution in the system K O-MnO-CuO-TeO under hydrothermal conditions at T ≤ 220 °C. Subeuhedral have been investigated by means single-crystal X-ray diffraction. The crystal structure this new zemannite-type representative adopts a monoclinic twofold superstructure. doubling unit-cell volume is accompanied hexagonal-to-monoclinic symmetry reduction, resulting threefold twinning with individual domains following space group P 1 . Refinements site-occupation factors and evaluation bond valences suggest distribution di- trivalent cations octahedrally coordinated M sites ratio (Cu + Mn ):Mn approximating 1:1. Based on arguments about cation sizes valence sums, Cu 1– x each two four can be assumed between ~ 0.14 0.50. H molecules inside channels are located off central channel axis. In contrast to most other known phases, extra-framework atoms show full occupancies not disordered. contents supports anisotropic deformation surrounding framework, which follows local reduction as required for Jahn-Teller distortion within framework. arrangement deformed understood origin existing