Synthesis and structural characterization of a calcium coordination polymer based on a mu (3) -bridging tetradentate binding mode of glycine

Abstract

A new coordination polymer namely [[Ca-6(H-gly)(12)(H2O)(18)]Cl-12.6H(2)O](n) (1) (H-gly = glycine) has been isolated from the calcium chloride-glycine-water system and structurally characterized. Each Ca(II) in 1 is eight-coordinated and is bonded to eight oxygen atoms three of which are from terminal water molecules and five oxygen atoms from four symmetry related zwitterionic glycine ligands. The H-gly ligands exhibit two different binding modes viz., a monodentate carboxylate ligation and a mu(3)-tetradentate bridging carboxylate binding mode, which results in the formation of a one-dimensional coordination polymer. In the infinite chain the Ca(II) atoms are organized in a zigzag fashion. A comparative study reveals a rich and diverse structural chemistry of calcium halide-glycine compounds.