catena-Poly[4,4'-bipyridinium [[diaqua-disulfatocadmium(II)]-μ-4,4'-bipyridine-κN:N'] dihydrate].

The title compound, {(C(10)H(10)N(2))[Cd(SO(4))(2)(C(10)H(8)N(2))(H(2)O)(2)]·2H(2)O}(n), consists of anionic chains of the Cd complex, diprotonated 4,4'-bipyridinium cations and uncoordinated water mol-ecules. In the anionic chain, the Cd atom lies on a center of inversion in an octa-hedral geometry. The midpoint of the coordinated bipyridine also resides on a center of inversion, as does the non-coordinated bipyridinium counterion. O-H⋯O and N-H⋯O hydrogen bonding inter-actions and π-π stacking inter-actions in the structure are responsible for the supra-molecular assembly.