Diaqua-bis(2,2'-biimidazole)zinc(II) 4,4'-di-carboxybiphenyl-3,3'-di-carboxyl-ate.

In the title compound, [Zn(C(6)H(6)N(4))(2)(H(2)O)(2)](C(16)H(8)O(8)), the Zn(II) atom, located on an inversion centre, is coordinated by two aqua and two bidentate biimidizole ligands, resulting in a slightly distorted octa-hedral ZnO(2)N(4) geometry. The four N atoms from the two biimidizole ligands lie in the equatorial plane and the two aqua O atoms lie in the axial sites. The biphenyl-tetra-carboxyl-ate anion also lies on an inversion centre. The Zn(II) complex cation and the anion are held together by N-H⋯O hydrogen bonds, forming a zigzag chain along [21]. The chains are further connected by water mol-ecules via O-H⋯O hydrogen bonds.