2,3-Diamino-pyridinium 4-meth-oxy-quinoline-2-carboxyl-ate.

In the 4-meth-oxy-quinoline-2-carboxyl-ate anion of the title salt, C5H8N3(+)·C11H8NO3(-), the dihedral angle between the quinoline ring system and the carboxyl-ate group is 16.54 (15)°. In the crystal, the cations and anions are linked via N-H⋯O and N-H⋯N hydrogen bonds, forming a centrosymmetric 2 + 2 aggregate with R2(2)(9) and R4(2)(8) ring motifs. These units are further connected via N-H⋯O hydrogen bonds into a layer parallel to the bc plane. The crystal structure is also stabilized by weak C-H⋯O hydrogen bonds and π-π inter-actions between pyridine rings [centroid-centroid distance = 3.5886 (8) Å] and between pyridine and benzene rings [centroid-centroid distance = 3.6328 (8) Å].