Syntheses, structures, thermal stabilities and bacteriostatic activities of four lanthanide complexes

Abstract

Four lanthanide complexes, [La2(2,4-DClBA)6(5,5′-DM-2,2′-bipy)2(H2O)2]·2C2H5OH (1) and [Ln(2,4-DClBA)3(5,5′-DM-2,2′-bipy)(C2H5OH)]2 (Ln = Pr(2), Sm(3), Gd(4); 2,4-DClBA = 2,4-dichlorobenzoate; 5,5′-DM-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine), were synthesized and characterized via elemental analysis, infrared spectra and thermogravimetric analysis (TG). The crystal structures of 1 and 2–4 are different; Each La3+ is nine-coordinate adopting a distorted mono-capped square antiprism, while the Ln3+ ions of 2–4 are all eight-coordinate with a distorted square antiprismatic molecular geometry. There are subtle changes in the local coordination geometry of the lanthanide–5,5′-DM-2,2′-bipy complexes. Binuclear 1 complexes are stitched together via two kinds of hydrogen bonding interactions (OH⋯O and CH⋯O) to form 1-D chains along the y axis, while the units of 2–4 are stitched together via CH⋯O to form 1-D chains along the x axis. TG analysis revealed thermal decomposition processes and thermal stabilities of the complexes. The bacteriostatic activities of the complexes were evaluated against Candida albicans, Escherichia coli, and Staphylococcus aureus.