The crystal structure of a new polymorph of hexa-aqua-nickel(II) bis-(6-oxo-1,6-di-hydro-pyridine-3-carboxyl-ate).

In a new polymorph of the title salt, [Ni(H2O)6](C6H4NO3)2, the metal atom of the cationic complex lies on a symmetry centre and is coordinated by six water mol­ecules to provide a quite regular octa­hedral coordination environment. These cations inter­act with 6-oxo-1,6-di­hydro­pyridine-3-carboxyl­ate anions through electrostatic inter­actions and by means of O—H⋯O and N—H⋯O hydrogen bonds involving the carboxyl­ate, keto and protonated imine groups of the anion, and the coordinating water mol­ecules from the cationic complex entity to generate a supra­molecular three-dimensional architecture. The previously reported polymorph of this compound presents a network of hydrogen bonds, in which the organic anions establish mutual hydrogen-bonding inter­actions involving their keto and protonated imine groups.