Crystal structure of bis[4-(di-methyl-amino)-pyridinium] bis(2-nitro-benzoate) trihydrate

The title salt, 2C7H11N2 (+)·2C7H4NO4 (-)·3H2O, crystallized with two anions and two cations in the asymmetric unit, together with three water mol-ecules. Both 4-di-methyl-amino-pyridinium cations are protonated at their pyridine N atoms with the plane of the N(CH3)2 hetero atoms inclined to the pyridine ring by 4.5 (2) and 1.4 (2)°. In the 2-nitro-benzoate 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 mol-ecules, 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 inter-actions [inter-centroid distances range from 3.617 (1) to 3.851 (1) Å], forming a three-dimensional structure.