Rational design of cobalt molecular square complexes with exact coplanar corners by bis-chelating 4,5-imidazoledicarboxylate bridges

The imidazole-based ligand imidazoledicarboxylic acid (H3IDC) has been successfully employed in the rational design and syntheses of two cobalt square complexes. Assemblies in hydrothermal conditions between two types of angular units (A) CoIII(bipy) or CoIII(phen) and the fully deprotonated ion IDC3− acting as the linear unit (L), bring two discrete tetranuclear complexes [CoIII4(IDC3−)4(bipy)4]·15H2O (1) and [CoIII4(IDC3−)4(phen)4]·17H2O (2). The X-ray single crystal analyses demonstrated that the cobalt ions are exact coplanar in square geometry. And elemental analysis and thermogravimetric analysis (TGA) with single crystal samples have been performed. These results suggest that the linear bis(bidentate) linkers have large potential to construct discrete molecular metallacycles.

Graphical abstractThe bis(bidentate) ligand imidazoledicarboxylic acid (H3IDC) has been successfully employed in the rational design and syntheses of two cobalt square complexes. Assemblies in hydrothermal conditions between two types of angular units (A) CoIII(bipy) or CoIII(phen) and the fully deprotonated ion IDC3− acting as the linear unit (L), bring two discrete tetranuclear complexes [CoIII4(IDC3−)4(bipy)4]·15H2O (1) and [CoIII4(IDC3−)4(phen)4]·17H2O (2). The X-ray single crystal analyses demonstrated that the cobalt ions are exact coplanar in square geometry. And elemental analysis and thermogravimetric analysis (TGA) with single crystal samples have been performed. These results suggest that the linear bis(bidentate) linkers have large potential to construct discrete molecular metallacycles.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two angular units (A) CoIII(bipy) or CoIII(phen) and the linear unit (L) IDC3−. ► Two discrete tetranuclear complexes. ► The cobalt ions in two compounds are exact coplanar. ► The linear IDC3− with large potential to construct discrete molecular metallacycles.