4-(4-Pyridyl)pyridinium 3′,4,4′-tricarboxybiphenyl-3-carboxylate dihydrate

Abstract

In the title compound, C10H9N2+·C16H9O8−·2H2O, both the cation and anion possess crystallographically imposed centres of symmetry, causing the nitrogen-bound H atom in the 4-(4-pyridyl)pyridinium cation and the acidic H atom of the carboxylate groups at the 3 and 3′ positions in the anion to be disordered over two positions with equal occupancies. In the crystal packing, the cations, anions and water molecules are connected by O—H...O, C—H...O and N—H...N hydrogen bonds, forming layers parallel to (2overline{1}0). These layer are further connected into a three-dimensional supramolecular network by O—H...O hydrogen bonds involving the water molecules as H-atom donors and by weak π–π stacking interactions between neighbouring benzene and pyridine rings, with centroid–centroid distances of 3.756 (5) Å.