The title compound, [Ni(C7H3NO4)(C12H8N2)(H2O)]- C7H5NO44H2O or [Ni(pydc)(phen)(H2O)].pydcH24H2O, was obtained by the reaction of nickel(II) nitrate hexahydrate with the proton-transfer compound (phenH)2(pydc) (phen is 1,10-phenanothroline and pydcH2 is pyridine-2,6-dicarboxylic acid) in aqueous solution. Both the cationic and anionic portions of the starting proton-transfer compound are involved in the complexation. The NiII atom has a distorted octahedral geometry and is hexacoordinated by three O atoms and three N atoms from one phen fragment (as a bidentate ligand), one (pydc)2 unit (as a tridentate ligand) and one water molecule. In the crystal structure, extensive O—H O, O—H N and C—H O hydrogen bonds with D A distances ranging from 2.573 (2) to 3.385 (2) A ° , – interactions between the phen ring systems [with centroid–centroid distances of 3.4694 (12), 3.4781 (11) and 3.8310 (11) A ° ] and intermolecular C—O interactions [C distances of 3.4812 (17), 3.5784 (16) and 3.5926 (16) A ° ] connect the various components together.
