Synthesis, crystal structures, luminescence and thermal properties of lanthanide complexes containing 2,5-dichlorobenzoic acid and 2,2:6′,2-terpyridine

Three novel ternary lanthanide complexes [Ln(2,5-DClBA)(3)(terpy)(H2O)] (Ln = Eu (1), Tb (2), Ho (3), 2,5-DClBA = 2,5-dichlorobenzoate, terpy = 2,2:6',2aEuro(3)-terpyridine) have been successfully synthesized and characterized by single-crystal and powder X-ray diffraction. Complexes 1-3 are isostructural, and each metal center is nine-coordinated with distorted monocapped square antiprismatic coordination geometry. The mononuclear units are assembled into 1D, 2D, 3D supramolecular structures by the pi-pi stacking and halogen-halogen interactions. Thermal decomposition mechanisms of the title complexes were investigated by thermogravimetric analysis and further authenticated by TG/DSC-FTIR techniques. The solid-state fluorescent properties of complexes 1-2 were studied at room temperature, and characteristic emission was observed for all complexes. Complex 1 exhibits the strong red emission, while the complex 2 is green under UV light. Moreover, the antibacterial activities of the complexes against Candida albicans, Escherichia coli and Staphylococcus aureus were also evaluated.