The asymmetric unit of the title compound, (C6H9N2)- [Co(C7H3NO4)(C7H4NO4)]C7H5NO43H2O, contains one (6- carboxypyridine-2-carboxylato)(pyridine-2,6-dicarboxylato)- cobaltate(II) anion, one phenylhydrazinium cation, one pyridine-2,6-dicarboxylic acid molecule and three uncoordinated water molecules, part of which are disordered. The CoII ion is coordinated by a pyridine-2,6-dicarboxylate ion and a 6- carboxypyridine-2-carboxylate ligand almost perpendicular to each other [the angle between the least-squares planes is 87.38 (4)] and is surrounded by two O atoms and two N atoms in the equatorial plane and two O atoms in axial positions, resulting in a distorted octahedral coordination geometry. There is an extensive three-dimensional network of O—H O and N—H O hydrogen bonds, which link the components.
