4,4′-Bipyridinium bis(μ-4-oxo-1,4-dihydropyridine-2,6-dicarboxylato)bis[aquahydroxidoantimonate(III)] dihydrate

The title compound, (C10H10N2)[Sb2(C7H2NO5)2(OH)2(H2O)2]·2H2O, consists of a binuclear anion, a diprotonated 4,4′-bipyridinium cation and two uncoordinated water molecules. Each SbIII atom is six-coordinated by one chelating 4-oxidopyridine-2,6-dicarboxylate ligand, one water molecule, one OH group and one bridging O atom from a neighboring carboxylate group in a distorted pentagonal-pyramidal geometry, with the OH group at the apical position. The two pyridine rings in the bipyridinium cation are twisted with respect to each other, making a dihedral angle of 22.7 (1)°. The cations are connected to the anions by N—H...O hydrogen bonds, forming a chain. The coordinated water molecules form hydrogen bonds with the oxido O atoms of the anion, building a two-dimensional sheet, which is further connected into a three-dimensional structure by O—H...O and C—H...O hydrogen bonds and C=O...π interactions [O...centroid distances = 3.1785 (17), 3.4737 (19) and 3.5685 (19) Å]