Crystal structure of poly[[{μ2-1,4-bis[(1H-imid-azol-1-yl)methyl]benzene}[μ6-5-(4-carboxylatophenoxy)isophthalato]-μ3-hydroxido-dicobalt(II)] 0.25-hydrate].

The title coordination polymer, {[Co2(C15H7O7)(OH)(C14H14N4)]·0.25H2O} n , was synthesized under hydro-thermal conditions. The asymmetric unit contains two Co(2+) ions, one L (3-) anion originating from 5-(4-carb-oxy-phen-oxy)isophthalic acid (H3 L), one OH(-) ligand, one 1,4-bis-[(1H-imidazol-l-yl)meth-yl]benzene (bix) ligand and one disordered lattice water mol-ecule (occupancy 0.25). The two Co(2+) ions have different environments. One has an octa-hedral O4N2 coordin-ation sphere, defined by four O atoms from three carboxyl-ate groups and one OH(-) ligand, and two N atoms from two symmetry-related bix ligands. The other has a trigonal-bipyramidal O5 coordination sphere resulting from three carboxyl-ate groups and two OH(-) ligands. The dihedral angles between the two benzene rings in the L (3-) ligand and between the benzene ring and the two imidazole rings in the bix ligand are 67.05 (15), 75.27 (17) and 82.05 (17)°, respectively. Four neighbouring Co(2+) ions are linked by six carboxyl-ate groups and two μ 3-OH ligands, forming a butterfly-shaped secondary building unit (SBU). These SBUs are connected by L (3-) anions into layers parallel to (1-10). Adjacent layers are cross-linked by the bix ligands, forming a three-dimensional framework that has a bimodal (3,8)-connected tfz-d topology. The disordered lattice water mol-ecule is located in the voids of the framework and has O⋯O and O⋯N contacts of 2.81 (2) and 2.95 (2) Å, suggesting medium-strength hydrogen bonds. The title compound may be a good candidate for artificial eye lenses.