Diaquabis(2,2′-biimidazole)cobalt(II) 4,4′-dicarboxybiphenyl-3,3′-dicarboxylate

In the title compound, [Co(C6H6N4)(2)(H2O)(2)](C16H8O8), the Co-II cation and the organic anion occupy different crystallographic inversion centres and, as a consequence, the asymmetric unit comprises two half-molecules. The benzene groups are coplanar. The four coordinating N atoms of the two bidentate biimidazole ligands define the equatorial plane of a slightly distorted octahedral CoO2N4 geometry, and the water O atoms lie in the axial coordination sites. Translational (a, (b) over bar) and inversion-related symmetry operations link the Co complex molecules and the negatively charged carboxylate anions via intermolecular N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds into sheets parallel to ((1) over bar 01). The coordinated water molecules connect the sheets through O-H center dot center dot center dot O hydrogen bonds, forming a three-dimensional framework. In addition, two intramolecular O-H center dot center dot center dot O hydrogen bonds are observed between the carboxyl and carboxylate groups.