Ligand-controlled assembly of cobalt(II) metal–organic complexes from different semirigid bis(imidazole) derivatives and aromatic monocarboxylates: Electrochemical behaviors and fluorescent properties

To explore the influence of the conformation and substitute group of organic ligands on constructing coordination polymers, we synthesized four Co(II) metal–organic complexes, namely, [Co(bix)(BBA)2]2 (1), [Co(bix)(DNBA)2] (2), [Co(dmpbbbm)(BBA)2] (3) and [Co(dmpbbbm)(DNBA)(Cl)] (4) (bix = 1,4-bis(imidazol-1-ylmethyl)benzene, dmpbbbm = 1,4-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, HBBA = 4-bromobenzoic acid, HDNBA = 3,5-dinitrobenzoic acid) under hydrothermal conditions. Complex 1 is a dinuclear cluster and is finally extended into a one-dimensional (1D) supramolecular chain though H-bonding interactions. Complex 2 shows 1D right-handed helical chains. Complex 3 possesses meso-helical chains with left- and right-handed helix, which is further extended into a two-dimensional (2D) supramolecular wave-like network through π–π stacking interactions. Complex 4 exhibits a meso-helical chain with left- and right-handed helical loops in one single strand, which is ultimately packed into a three-dimensional (3D) supramolecular framework through π–π stacking interactions. In addition, the thermal stability, the fluorescent properties and the electrochemical behaviors of the title complexes at room temperature have been investigated.