Acridin-10-ium 6-carb­oxy­pyridine-2-carboxyl­ate

The title compound, C(13)H(10)N(+)·C(7)H(4)NO(4) (−), consists of a protonated acridinium cation and a 6-carb­oxy­pyridine-2-carboxyl­ate monoanion. The carboxyl­ate group of the anion appears to be delocalized on the basis of the nearly equivalent C—O bond lengths. In the crystal, the anions are connected by strong O—H⋯O hydrogen bonds, forming chains along the b axis. The acridinium cations are linked to the anionic chains by strong N—H⋯O hydrogen bonds between the carboxyl­ate group of the anion and the N—H group of the cation. Along the b axis, successive chains stack in opposite directions. Weak inter­molecular C—H⋯O hydrogen bonds further stabilize the crystal structure.