Bis(1H-imidazole-κN3)bis(2-oxidopyridinium-3-carboxylato-κ2O2,O3)nickel(II)

In the crystal structure of the title NiII complex, [Ni(C6H4NO3)2(C3H4N2)2], the NiII atom is located on a twofold rotation axis and is chelated by two oxidopyridiniumcarboxylate anions and further cis-coordinated by two imidazole ligands in a distorted cis-N2O4 octahedral geometry. The C—O bond distance of 1.2573 (19) Å found for the non-coordinating O atom of the carboxylate group indicates significant delocalization of π-electron density over this residue. Similarly, the C—O bond distance of 1.260 (2) Å in the heteroaromatic ring indicates delocalization between the deprotonated hydroxy group and the pyridinium ring. The uncoordinated carboxylate O atom links with the imidazole and pyridinium rings of adjacent molecules via N—H...O and C—H...O hydrogen bonding, leading to a two-dimensional array parallel to (100).