On Two Glycine Zinc Sulfate Phases with Exotic Cation Coordination Geometries

Abstract

Two hitherto hardly characterized glycine zinc sulfates were identified in the product of a batch production process for glycine zinc sulfates of the BASF Company: Gly·ZnSO4·2H2O and β-Gly-ZnSO4. The crystal structures were solved from high resolution synchrotron X-ray powder diffraction data. Gly·ZnSO4·2H2O is the zinc analogue to an isotypic copper compound with space group P21/c (no. 14) and a = 7.8092(1) Å, b = 12.3979(2) Å, c = 8.3732(1) Å, β = 90.673(1) and V = 810.62(2) ų. The crystal structure of the hitherto unknown β-Gly-ZnSO4 with space group P21/c (no. 14) and a = 9.2577(1) Å, b = 5.1268(1) Å, c = 12.9926(1) Å, β = 90.267(1) and V = 616.65(1) Å3 was solved ab initio. In both crystal structures the zinc cations exhibit exotic, fivefold coordination arrangements: squared ZnO5-pyramids are present in the structure of the dihydrate, whereas the crystal structure of β-Gly-ZnSO4 contains trigonal ZnO5-bipyramids.