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.

Graphical abstractFour 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) have been synthesized from hydrothermal reactions. The conformation and substitute groups of ligands have a great influence on the construction of title complexes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Semirigid dmpbbbm were used as N-donor ligand, which has not been reported. ► Complex 1 displays a dinuclear cluster and 2–4 exhibit helical or meso-helical chain. ► The conformation and substitute group of ligands have influence on the complexes.