Construction of 0D, 1D and 2D cobalt(II) complexes containing flexible bis(benzimidazole) and dicarboxylic acid ligands

Three complexes {[Co-0.5(HL1)(H2O)(2)]center dot(tbta)} (n) (1), [Co-0.5(L2)(ndc)(0.5)] (n) (2) and [Co(L3)(tp)] (n) (3) (L1 = 1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H(2)tbta = tetrabromoterephthalic acid, L2 = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H(2)ndc = 2,6-naphthalenedicarboxylic acid, L3 = 1,3-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H(2)tp = 1,4-benzenedicarboxylic acid) based on flexible bis(benzimidazole) derivatives have been synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as single-crystal X-ray diffraction analysis. The analysis reveals that complex 1 features a mononuclear structure, which is further assembled into a 2D supermolecular framework via O-H center dot center dot center dot O hydrogen bond interactions. Complex 2 shows a 1D zigzag chain connected by ndc(2-) ligands, while 3 exhibits a 2D 4-connected layer and ultimately is extended into a 3D supramolecular network through two kinds of pi center dot center dot center dot pi stacking interactions. Moreover, the fluorescence and catalytic properties of the complexes for the degradation of the Congo red azo dye in a Fenton-like process are discussed.