Bis(2,6-diamino­pyridinium) tartrate monohydrate

In the title compound, 2C(5)H(8)N(3) (+)·C(4)H(4)O(6) (2−)·H(2)O, the two cations are essentially planar [maximum deviations = 0.023 (1) and 0.026 (1) Å]. 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⋯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⋯O and C—H⋯O hydrogen bonds. The cations further link the anions and water mol­ecules into a three-dimensional extended structure by a network of N—H⋯O hydrogen bonds. The crystal structure is also stabilized by weak inter­molecular π–π inter­actions [centroid–centroid distance = 3.6950 (6) Å].