Studies on DNA Interactions and Biological Activities of Lanthanum(III) Complexes with 4-Quinoline Terpyridine and 1,10-Phenanthroline

Abstract

A series of lanthanum(III) complexes [La(4-qtpy)2(NO3)2](NO3) (1), [La(4-qtpy)3(NO3)](NO3)2 (2), [La(4-qtpy)(phen)(NO3)2](NO3) (3) and [La(4-qtpy)(phen)2(NO3)2](NO3) (4) (4-qtpy = 4′-[(4-quinoline)-2,2′;6′,2′′-terpyridine]) were synthesized and characterized. The cyclic voltammetric studies revealed that the complexes 1 and 3 are redox active. UV-visible absorption spectral studies and viscosity measurements revealed that complexes bind to DNA through intercalation. Complexes 1 and 3 have shown the highest binding propensity (Kb = 4.241 + 0.2 × 106 for 1 and 1.492 + 0.2 × 106 for 3). The results of chemical nuclease studies revealed that the complexes 3 and 4 have shown maximum chemical nuclease activity in the presence of H2O2 and the mechanism involves hydroxyl radicals. The antibacterial activities of the complexes 1 to 4 were tested against Gram positive and Gram negative bacteria in which complex 3 shows comparable results with the standard antibiotic tetracycline. The cytotoxic activities of 4-qtpy and complex 4 were done by MTT assay against HeLa cell lines.