Bis(2,6-diaminopyridinium) tartrate monohydrate

In the title compound, 2C(5)H(8)N(3)(+)center dot C(4)H(4)O(6)(2-)center dot H(2)O, the two cations are essentially planar [maximum deviations = 0.023 (1) and 0.026 (1) angstrom]. In one of the cations, the protonated N atom and one of the amino group H atoms are hydrogen bonded to one of the carboxyl groups of the dianion through a pair of N-H center dot center dot center dot O hydrogen bonds, forming an R(2)(2)(8) ring motif. In the crystal structure, the tartrate anions and water molecules are linked into chains along the c axis by intermolecular O-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds. The cations further link the anions and water molecules into a three-dimensional extended structure by a network of N-H center dot center dot center dot O hydrogen bonds. The crystal structure is also stabilized by weak intermolecular pi-pi interactions [centroid-centroid distance = 3.6950 (6) angstrom]