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

The title salt, 2C7H11N2+ 2C7H4NO4- 3H2O, 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(CH3)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.