3,4-Diamino­pyridinium 4-nitro­benzoate–4-nitro­benzoic acid (1/1)

In the title compound, C(5)H(8)N(3) (+)·C(7)H(4)NO(4) (−)·C(7)H(5)NO(4), the non-H atoms of the 3,4-diamino­pyridinium cation are coplanar, with a maximum deviation of 0.022 (1) Å. The carboxyl­ate and nitro groups of the 4-nitro­benzoate anion are twisted out of the attached ring planes by dihedral angles of 15.89 (8) and 10.20 (8)°, respectively. In the 4-nitro­benzoic acid mol­ecule, the carboxyl and nitro groups form dihedral angles of 18.25 (8) and 6.55 (8)°, respectively, with the benzene ring. In the crystal, the constituent units form two-dimensional networks parallel to (001) by O—H⋯O, N—-H⋯O and C—H⋯O hydrogen bonds. Weak π–π inter­actions involving inversion-related 4-nitro­benzoic acid mol­ecules [centroid–centroid distance = 3.7325 (8) Å] and inversion-related 4-nitro­benzoate mol­ecules [centroid–centroid distance = 3.7124 (8) Å] are also observed.