The title polymeric compound, [Cd(C7H3NO4)(H2O)3]n or [Cd(py-2,3-dc)(H2O)3]n, where py-2,3-dcH2 is pyridine-2,3- dicarboxylic acid, was obtained by the reaction of cadmium(II) nitrate hexahydrate with (pipzH2)(py-2,3-dc) as a proton-transfer compound in aqueous solution (pipz is piperazine). The molecular structure shows that only the anionic fragment of the starting proton-transfer compound is present in the complex, while the (pipzH2)2+ dication has been lost. Each (py-2,3-dc)2 ligand bridges two CdII atoms in two different coordination modes, i.e. one end acts as a monodentate and the other end as a bidentate ligand. The three remaining coordination sites on the metal center are occupied by water molecules. The geometric arrangement of the six donor atoms around the CdII atom is distorted octahedral. In the crystal structure, O—H O and C—H O hydrogen bonds play an important role in stabilizing the supramolecular structure.
