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 mol-ecules to provide a quite regular octa-hedral coordination environment. These cations inter-act with 6-oxo-1,6-di-hydro-pyridine-3-carboxyl-ate anions through electrostatic inter-actions and by means of O-H⋯O and N-H⋯O hydrogen bonds involving the carboxyl-ate, keto and protonated imine groups of the anion, and the coordinating water mol-ecules from the cationic complex entity to generate a supra-molecular 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 inter-actions involving their keto and protonated imine groups.
Keywords: 6-oxo-1,6-dihydropyridine-3-carboxylate anion; crystal structure; hydrogen bonding,; polymorph.