Cobalt (II) coordination polymers based on 3,5-dinitrobenzoate and flexible bis(benzimidazole) derivatives bearing different spacer lengths and substituents

摘要

Three new Co~(II) coordination polymers, namely [Co(DNBA)2(pbdmbm)] (1), [Co2(H2O)2(DNBA)2(ebdmbm)2] (2) and [Co2(DNBA)2(pbbm)2] (3) have been obtained by hydrothermal reactions of Co~(II) with flexible bis(benz-imidazole) ligands [1,1'-(1,3-propanediyl)bis(5,6-dimeth-ylbenzimidazole) (pbdmbm), 1,1'-(1,2-ethanediyl)bis(5,6-dimethylbenzimidazole) (ebdmbm), 1,1'-(1,3-propanediyl) bis(benzimidazole) (pbbm)] plus 3,5-dinitrobenzoic acid (HDNBA). The complexes have been characterized by single crystal X-ray diffraction, elemental analyses, IR and TG. Complexes 1 and 3 exhibit one-dimensional chains composed of Co~(II) centers bridged by flexible bis(benz-imidazole) ligands. Complex 2 is a three-dimensional NaCl-type supramolecular framework constructed from binuclear units, which are formed by two Co~(II) centers and two ebdmbm ligands. The spacer length and substituents on the bis(benzimidazole) ligands are crucial for the construction of these structures. The photoluminescence properties of the complexes and the cyclic voltammetry behavior of complex 1 are described.