2-Amino-4-methylpyridinium 6-carboxypyridine-2-carboxylate sesquihydrate

In the title compound, C6H9N2+·C7H4NO4−·1.5H2O, extensive O—H...O, O—H...N, N—H...O and C—H...O hydrogen bonds, as well as ion pairing, π–π stacking interactions [centroid–centroid distances = 3.4690 (8) and 3.6932 (8) Å between aromatic rings] occur in the crystal. There are hydrogen-bonding interactions between water molecules, which result in cyclic tetrameric water clusters. One of the water O molecules has half occupancy. In the anion molecules, the –CO2 and –CO2H groups make torsion angles of 1.73 (18) and −12.14 (18)° with respect to the ring