Synthesis, crystal structure and infrared spectroscopy of a novel copper strontium formate: CuSr(HCOO)4(H2O)2

Abstract

The title compound CuSr(HCOO)4(H2O)2 (1) forms a 3D polymeric structure, which basic structural units are SrO9 polyhedra in the form of monocapped square antiprisms and distorted CuO6 octahedra. The former groups organize as strips running parallel to the unique b axis, while interconnected by the latter into a strongly linked 3D covalent network.The infrared spectra of (1) confirm the existence of four nonequivalent formate groups with large deviations from C2v molecular symmetry. The frequencies of the OD modes (isotopically dilute samples) are assigned on the basis of the respective intermolecular Ow⋯O bond lengths, the metal−water interactions (synergetic effect) and the different hydrogen bond acceptor capability of the oxygen atoms. The hydrogen bond acceptor strengths of the formate oxygen atoms are discussed within the framework of the Brown’s bond–valence theory. Intramolecular OH distances are derived from the novel νOD versus rOH correlation curves [J. Mol. Struct. 351 (1995) 205; J. Mol. Struct. 404 (1997) 63)]. The librations of the water molecules are also discussed.