Three nickel(II) coordination polymers with flexible bis(benzimidazole) and tetrabromoterephthalate ligands

Abstract

By tuning the spacer length of flexible bis(5,6-dimethylbenzimidazole) ligands, three nickel(II) coordination polymers {[Ni(L1)(tbta)(H2O)2]·H2O} n (1), {[Ni(L2)(tbta)(H2O)2·H2O]} n (2) and {[Ni(L3)2(tbta)]·5H2O} n (3) (L1 = 1,4-bis(5,6-dimethylbenzimidazole)butane, L2 = 1,3-bis(5,6-dimethylbenzimidazole)propane and L3 = 1,1′-bis(5,6-dimethylbenzimidazole)methane, H2tbta = tetrabromoterephthalic acid) were synthesized under hydrothermal conditions. These complexes were characterized by physico-chemical and spectroscopic methods and by single-crystal diffraction. All the three complexes feature 2D {44·62} sql/Shubnikov tetragonal plane networks. Complex 1 is further extended into a 3D supramolecular framework via weak C–H···O hydrogen-bonding interactions. Complex 3 shows a 3D supramolecular network through π–π stacking interactions. The fluorescence properties and catalytic activities of these complexes for the degradation of Congo red azo dye in a Fenton-like process were investigated.