| Summary: | The title coordination polymer, {[Co2(C15H7O7)(OH)(C14H14N4)]·0.25H2O}n, was synthesized under hydrothermal conditions. The asymmetric unit contains two Co2+ ions, one L3− anion originating from 5-(4-carboxyphenoxy)isophthalic acid (H3L), one OH− ligand, one 1,4-bis[(1H-imidazol-l-yl)methyl]benzene (bix) ligand and one disordered lattice water molecule (occupancy 0.25). The two Co2+ ions have different environments. One has an octahedral O4N2 coordination sphere, defined by four O atoms from three carboxylate 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 carboxylate groups and two OH− ligands. The dihedral angles between the two benzene rings in the L3− 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 Co2+ ions are linked by six carboxylate groups and two μ3-OH ligands, forming a butterfly-shaped secondary building unit (SBU). These SBUs are connected by L3− 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 molecule 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.
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