Piperazinediium bis­(2-carboxy­pyridine-3-carboxyl­ate)

The asymmetric unit of the title salt, C(4)H(12)N(2) (2+)·2C(7)H(4)NO(4) (−) or pipzH(2) (2+)·2(py-2,3-dcH(−)), prepared by a reaction between pyridine-2,3-dicarboxylic acid (py-2,3-dcH(2)) and piperazine (pipz), contains a monoanion and half of a centrosymmetric dication. The anionic fragment individually has two intra­molecular hydrogen bonds, an almost linear O—H⋯O bond between two carboxyl­ate groups and a C—H⋯O bond between the aromatic ring and carboxyl­ate group. Other O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds are responsible for three-dimensional expansion of the structure.