Five coordination polymers based on two asymmetric Semi-rigid carboxylate organic ligands and N-donor 4, 4′-di (1H-imidazol-1-yl)-1, 1′-biphenyl ligand: Solvent-induced synthesis, crystal structures, magnetic and dye absorption properties

Abstract Five novel coordination polymers (CPs) [Co(pmb)(bibp)]n (1, 2), [Co3(cpa)2(bibp)3·H2O]n (3), [Ni3(cpa)2(bibp)3·4H2O]n (4) and [Cd3(cpa)2(bibp)3]n (5), have been prepared by employing two asymmetric semi-rigid carboxylate organic ligands (H2pmb = 4-(4-carboxyphenoxy)-3-methoxybenzoic acid, H3cpa = 3-(4-carboxy-2-methoxyphenoxy) phthalic acid) and one N-containing ligand (bibp = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl) under hydrothermal conditions. Interestingly, single crystal X-ray analysis reveals that compounds 1 and 2 feature differently structural frameworks despite using the same ligands and metal ion Co(II) but different solvents. Compound 1 has an 8-fold interpenetrated 3D net topology, while compound 2 has a 2D net topology. This study shows a controllable regulation of framework by changing solvent type in isomers CPs. Compounds 3, 4 and 5 are isomorphic, which exhibit uniform 3, 4-connected 3D net topology. The dye adsorption studies of 1 and 2 revealed that rapid uptake for methyl orange (MO) can be attributed to the porous character and charge properties of CPs. In addition, magnetic susceptibility measurements of compounds 1, 2 and 3 reveal predominant antiferromagnetic exchange interactions between central Co(II) ions.