Tetra­imidazolium piperazinediium bis­(benzene-1,3,5-tricarboxyl­ate) dihydrate

During the crystallization of the title compound, 4C3H5N2 +·C4H12N2 +·2C9H3O6 3−·2H2O, the acidic protons were transferred to the imidazole and piperazine N atoms, forming the final 4:1:2:2 hydrated mixed salt. The mean planes of the three carboxyl­ate groups in the anion are twisted with respect to the the central benzene ring, making dihedral angles of 13.5 (1), 14.5 (1) and 16.9 (1)°. In the crystal, the component ions are linked into a three-dimensional network by a combination of inter­molecular N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds. Further stabilization is provided by π-π stacking inter­actions with centroid–centroid distances of 3.393 (2) Å and weak C=O⋯π inter­actions [O–centroid = 3.363 (2) Å]