4,4'-Bipyridinium bis-(μ-4-oxo-1,4-dihydropyridine-2,6-dicarboxyl-ato)bis-[aqua-hydroxido-anti-monate(III)] dihydrate.

The title compound, (C(10)H(10)N(2))[Sb(2)(C(7)H(2)NO(5))(2)(OH)(2)(H(2)O)(2)]·2H(2)O, consists of a binuclear anion, a diprotonated 4,4'-bipyridinium cation and two uncoordinated water mol-ecules. Each Sb(III) atom is six-coordinated by one chelating 4-oxidopyridine-2,6-dicarboxyl-ate ligand, one water mol-ecule, one OH group and one bridging O atom from a neighboring carboxyl-ate group in a distorted penta-gonal-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 mol-ecules 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 inter-actions [O⋯centroid distances = 3.1785 (17), 3.4737 (19) and 3.5685 (19) Å].