4-Carboxypyridinium hydrogen chloranilate monohydrate

The title compound (systematic name: 4-carboxypyridinium 2,5-dichloro-4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-olate monohydrate), C ₆H₆NO₂⁺·C₆HCl ₂O₄^-·H₂O, is a monohydrate salt of chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) with isonicotinic acid (pyridine-4-carboxylic acid), in which an acid-base interaction involving a proton transfer is observed from the chloranilic acid to the pyridine group of isonicotinic acid. In the crystal structure, the 4-carboxypyridinium cation, the hydrogen chloranilate anion and the water molecule are held together through N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds, forming a chain. The chains are further linked by O-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional hydrogen-bond network.