Aqua(1,10-phenanthroline)(pyridine-2,6-dicarboxylato)nickel(II) pyridine-2,6-dicarboxylic acid solvate tetrahydrate

The title compound, [Ni(C7H3NO4)(C12H8N2)(H2O)]center dot-C7H5NO4 center dot 4H(2)O or [Ni(pydc)(phen)(H2O)].pydcH(2)center dot 4H(2)O, was obtained by the reaction of nickel(II) nitrate hexahydrate with the proton-transfer compound (phenH)(2)(pydc) (phen is 1,10-phenanothroline and pydcH(2) 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 Ni-II 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 center dot center dot center dot O, O-H center dot center dot center dot N and C-H center dot center dot center dot O hydrogen bonds with D center dot center dot center dot Lambda distances ranging from 2.573 (2) to 3.385 (2) angstrom, pi-pi interactions between the phen ring systems [with centroid-centroid distances of 3.4694 (12), 3.4781 (11) and 3.8310 (11) angstrom] and intermolecular C-O center dot center dot center dot pi interactions [C center dot center dot center dot pi distances of 3.4812 (17), 3.5784 (16) and 3.5926 (16) angstrom] connect the various components together.