A novel one-dimensional Co(II) coordination polymer: catena-poly[[hexaaquacobalt(II)] [[diaquabis(sulfato-κO)cobalt(II)]-μ-4,4'-bipyridine-κ2N:N'] [[triaqua(sulfato-κO)cobalt(II)]-μ-4,4'-bipyridine-κ2N:N']].

The title compound, {[Co(H(2)O)(6)][Co(SO(4))(C(10)H(8)N(2))(H(2)O)(3)][Co(SO(4))(2)(C(10)H(8)N(2))(H(2)O)(2)]}(n), contains three crystallographically unique Co(II) centres, all of which are in six-coordinated environments. One Co(II) centre is coordinated by two bridging 4,4'-bipyridine (4,4'-bipy) ligands, one sulfate ion and three aqua ligands. The second Co(II) centre is surrounded by two N atoms of two 4,4'-bipy ligands and four O atoms, i.e. two O atoms from two monodentate sulfate ions and two from water molecules. The third Co(II) centre forms part of a hexaaquacobalt(II) ion. In the crystal structure, there are two different one-dimensional chains, one being anionic and the other neutral, and adjacent chains are arranged in a cross-like fashion around the mid-point of the 4,4'-bipy ligands. The structure features O-H···O hydrogen-bonding interactions between sulfate anions and water molecules, resulting in a three-dimensional supramolecular network.