Exploring the effect of chain length of bridging ligands in cobalt(II) coordination polymers based on flexible bis(5,6-dimethylbenzimidazole) ligands: Synthesis, crystal structures, fluorescence and catalytic properties

Two new Co(II) metal organic coordination polymers have been hydrothermally synthesized using flexible bis(5,6-dimethylbenzimidazole) ligands with varying chain lengths with 5-nitroisophthalic auxiliary ligand. 1 features a 1D looped-like chain consisting of two kinds of macrocycles alternately, and 2 possesses a 4-connected twofold interpenetrating diamond network structure. Moreover, the two compounds as a heterogeneous catalysts present high efficiency for the degradation of methyl orange dye in Fenton-like process. [GRAPHICS] Two Co(II) coordination polymers derived from a dicarboxylate and two flexible bis(5,6-dimethylbenzimidazole) ligands with varying chain lengths equipped, namely [Co(bdmbmm)(nip)](n)(1) and [Co-2(bdmbmb)(2)(niP)(2 center dot)H2O](n) (2) (bdmbmm = 1,1'-bis(5,6-dimethylbenzimidazole)methane, H(2)nip = 5-nitroisophthalic acid, bdmbmb = 1,4-bis(5,6-dimethylbenzimidazole)butane), have been synthesized by hydrothermal methods and characterized by elemental analyses, IR spectra, thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD) and single-crystal X-ray diffraction. Complex 1 forms a 1D looped-like chain consisting of two kinds of macrocycles, which is further arranged into a 2D supramolecular layer through face-to-face pi-pi stacking interactions; whereas complex 2 exhibits a 3D framework with a twofold interpenetrating diamondoid topology. The fluorescence and catalytic properties of the complexes for the degradation of methyl orange by sodium persulfate have been investigated. (C) 2013 Elsevier B.V. All rights reserved.