catena-Poly[[[diaqua-(1,10-phenanthroline-κ(2) N,N')cobalt(II)]-μ-1H-benzimidazole-5,6-dicarboxyl-ato-κ(2) N (3):O (6)] sesquihydrate}.

In the title compound, {[Co(C9H4N2O4)(C12H8N2)(H2O)2]·1.5H2O} n , the Co(II) atom is hexa-coordinated by one N atom and one O atom from two symmetry-related 1H-benzimidazole-5,6-dicarboxyl-ate ligands, two N atoms from one 1,10-phenanthroline ligand (phen) and two water mol-ecules. The dihedral angle between the 1H-benzimidazole-5,6-dicarboxyl-ate and 1,10-phenanthroline ligands is 74.41 (4)°. The crystal packing is governed by inter-molecular O-H⋯O and N-H⋯O hydrogen-bonding inter-actions. All water (coordin-ating and lattice) mol-ecules take part in the hydrogen-bonding inter-actions. In addition, there are π-π stacking inter-actions between inversion-related phen ligands, the shortest centroid-centroid distance being 3.7536 (16) Å. One of the two lattice water molecules shows half-occupancy.