Cobalt(II) coordination polymers based on a semi-rigid bis(benzimidazole) ligand: From linear chain to 3D 3-fold interpenetrated diamond framework tuned by the auxiliary carboxylates

Abstract

Three new metal–organic coordination polymers, [Co2(bbix)3(dnba)4(H2O)]·0.5bbix (1), [Co(bbix)1.5(aip)]·H2O (2) and [Co(bbix)(fma)]·3H2O (3) (bbix=1,4-bis(benzimidazol-1-ylmethyl)benzene, Hdnba=3,5-dinitrobenzoate acid, H2aip=5-amino-isophthalic acid and H2fma=fumaric acid), were obtained under hydrothermal conditions and structurally characterized. Coordination polymer 1 shows a linear chain formed by dinuclear [Co2(dnba)4(H2O)] units and bbix ligands. The chains are further extended into a supramolecular layer by π–π stacking interactions between dnba and bbix. Coordination polymer 2 features a layer constructed from CoII ions and bbix ligands, and the aip anions only consolidate the layer structure. Coordination polymer 3 possesses a three-dimensional (3D) 3-fold interpenetrated diamond framework. In 3, the fma anions link the CoII ions to form a wave-like chain, which is further extended into a 3D architecture by the bbix ligands. The structural analyses clearly indicate that the nature of the secondary auxiliary ligands can effectively influence the coordination environments of the CoII ions and the dimensionality of the coordination polymers 1–3. In addition, the electrochemical and photoluminescent properties of 1–3, as well as magnetic properties of 1, have been investigated.