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

The title compound, [Ni(C(7)H(3)NO(4))(C(12)H(8)N(2))(H(2)O)]·C(7)H(5)NO(4)·4H(2)O or [Ni(pydc)(phen)(H(2)O)].pydcH(2)·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⋯O, O—H⋯N and C—H⋯O hydrogen bonds with D⋯A distances ranging from 2.573 (2) to 3.385 (2) Å, π–π inter­actions between the phen ring systems [with centroid–centroid distances of 3.4694 (12), 3.4781 (11) and 3.8310 (11) Å] and inter­molecular C—O⋯π inter­actions [C⋯π distances of 3.4812 (17), 3.5784 (16) and 3.5926 (16) Å] connect the various components together.