2-Amino-5-(4-carboxyl­atophen­yl)­pyridinium monohydrate

The title compound, C₁₂H₁₀N₂O₂·H₂O, crystallizes as a zwitterion in which the pyridine N atom is protonated and the carb­oxy –OH group is deprotonated. The benzene and pyridinium rings are inclined with a dihedral angle of 6.63 (5)° between them. In the crystal, inter­molecular O—H...O and N—H...O hydrogen-bonding inter­actions link adjacent mol­ecules into a two-dimensional double layered supra­molecular network.