Diaqua-bis(2,2'-biimidazole)cobalt(II) 4,4'-dicarboxy-biphenyl-3,3'-di-car-boxylate.

In the title compound, Co(C(6)H(6)N(4))(2)(H(2)O)(2), the Co(II) cation and the organic anion occupy different crystallographic inversion centres and, as a consequence, the asymmetric unit comprises two half-mol-ecules. The benzene groups are coplanar. The four coordinating N atoms of the two bidentate biimidazole ligands define the equatorial plane of a slightly distorted octa-hedral CoO(2)N(4) geometry, and the water O atoms lie in the axial coordination sites. Translational (a,) and inversion-related symmetry operations link the Co complex mol-ecules and the negatively charged carboxyl-ate anions via inter-molecular N-H⋯O and O-H⋯O hydrogen bonds into sheets parallel to (01). The coordinated water mol-ecules connect the sheets through O-H⋯O hydrogen bonds, forming a three-dimensional framework. In addition, two intra-molecular O-H⋯O hydrogen bonds are observed between the carboxyl and carboxyl-ate groups.