Cu20Sb35O44Br37 – one structure, two temperature dependencies

The structure of the new compound Cu20Sb35O44Br37 was examined at different temperatures and compared to the previously prepared structural analogue Cu20Sb35O44Cl37. The structure comprises two major units; isolated [Sb35O44Br5]12+ clusters shaped as typical sodalite building blocks (β-cages) and one-dimensional continuous CuBr chains of edge sharing super-tetrahedra. The covalent and ionic building blocks exhibit different temperature dependencies. While the CuBr substructure simply contracts with decreasing temperature, the disordered Sb35O44 part shows a more complex behaviour that can be understood in terms of weak, local, interactions becoming increasingly important at lower temperatures.

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