Metal-organophosphonates: hydrothermal synthesis and structures of [Cu(O3PC10H6CO2H)] and [Cu(bpy)(HO3PC10H6CO2)] (H2O3PC10H6CO2H = 2,6-carboxynaphthalene phosphonic acid)

Hydrothermal methods were used to prepare [Cu(O3PC10H6CO2H)] (1) and [Cu(bpy)(HO3PC10H6CO2)]·2H2O (2·2H2O), where H2O3PC10H6CO2H is 2,6-carboxynaphthalene phosphonic acid (H3cnp). The two-dimensional structure of 1 consists of layers of edge-sharing {CuO6} octahedra, producing an AlCl3- type structure of fused hexagonal rings of copper octahedra, enclosing voids of hexagonal profile. The layer composition is CuO3 or CuO6/2 as each oxygen bridges two copper sites. The Hcnp ligands project from either face of the copper “oxide” layer. Adjacent layers interact through hydrogen bonding interactions between the pendant –CO2H groups of the ligand. Coordination of the bipyridine ligand in [Cu(HO3PC10H6CO2)] (2) obstructs expansion in two-dimensions, and the material exhibits a chain structure. The chain is constructed of binuclear units of edge-sharing ‘4+1’ {CuO3N2} square pyramids linked through the dipodal {HO3PC10H6CO2}2− ligands.