Synthesis, crystal structure, cytotoxicity and DNA interaction of 5,7-dichloro-8-quinolinolato-lanthanides

Four isostructural lanthanide complexes with 5,7-dichloro-8-quinolinoline (H-ClQ): [Sm(ClQ)(3)(H(2)O)(2)]·1.33EtOH·0.33H(2)O (1), [Eu(ClQ)(3)(H(2)O)(2)]·0.5EtOH, (2), [Tb(ClQ)(3)(H(2)O)(2)]·0.5EtOH (3) and [Ho(ClQ)(3)(H(2)O)(2)]·H(2)O (4) were synthesized, in which the lanthanide was coordinated by three ClQ(-) anions and two aqua ligands. The in vitro cytotoxicities of complexes 1-4 against five human tumor cells were evaluated. The IC(50) values of complexes 1-4 against BEL7404, HeLa and A549 were in the range 1.2-6.3, 3.5-6.6 and 10.8-25.2 μM, respectively; except for complex 3 toward BEL7404, they all exhibited enhanced cytotoxicity in comparison to H-ClQ. The binding properties of complexes 1-4 to DNA examined by various methods indicated that complexes 1-4 interacted with DNA more strongly than free quinolinoline, and intercalation was the most probable binding mode for both the complexes and quinolinoline.