2-Amino-5-chloro­pyridinium (Z)-3-carb­oxy­prop-2-enoate 0.25-hydrate

In the title hydrated salt, C(5)H(6)ClN(2) (+)·C(4)H(3)O(4) (−)·0.25H(2)O, the water O atom lies on a twofold axis with 0.25 occupancy. The 2-amino-5-chloro­pyridinium cation is almost planar, with a maximum deviation of 0.015 (3) Å. In the hydrogen malate anion, an intra­molecular O—H⋯O hydrogen bond generates an S(7) ring and results in a folded conformation. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl­ate O atoms of the anion via a pair of N—H⋯O hydrogen bonds, forming an R (2) (2)(8) ring motif. The ion pairs are further connected via O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, forming layers parallel to the ab plane which stack down the c axis.