Crystal structure of bis[4-(di­methyl­amino)­pyridinium] bis(2-nitro­benzoate) trihydrate

The title salt, 2C(7)H(11)N(2) (+)·2C(7)H(4)NO(4) (−)·3H(2)O, crystallized with two anions and two cations in the asymmetric unit, together with three water mol­ecules. Both 4-di­methyl­amino­pyridinium cations are protonated at their pyridine N atoms with the plane of the N(CH(3))(2) hetero atoms inclined to the pyridine ring by 4.5 (2) and 1.4 (2)°. In the 2-nitro­benzoate anions, the carboxyl and nitro groups are inclined to their respective benzene rings by 77.1 (3) and 20.0 (3)°, and 75.8 (2) and 20.9 (3)°. In the crystal, the anions are linked via O—H⋯O hydrogen bonds involving the water mol­ecules, forming chains along [100]. The cations are linked to these chains by N—H⋯O hydrogen bonds. The chains are linked via C—H⋯O hydrogen bonds and C—H⋯π and π–π inter­actions [inter-centroid distances range from 3.617 (1) to 3.851 (1) Å], forming a three-dimensional structure.