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

Four mononuclear and iso-structural lanthanide complexes with 5,7-dibromo-8-quinolinol (H-BrQ): [Sm(BrQ)3(H2O)2]·0.5H2O (1), [Eu(BrQ)3(H2O)2]·1.33EtOH·0.33H2O (2), [Tb(BrQ)3(H2O)2]·0.5H2O (3), and [Dy(BrQ)3(H2O)2]·1.167EtOH·0.33H2O (4) were synthesized. Against BEL7404, SGC7901 and A549, complexes 1−4 exhibited enhanced cytotoxicity than H-BrQ or the corresponding lanthanide salts. The IC50 values of complexes 1, 3 against BEL7404 were 9.6 ± 2.2 and 10.1 ± 2.6 μM, while that of complex 4 against SGC7901 was 7.5 ± 2.1 μM. Complexes 1−4 against A549 yielded IC50 values in the range of 7.6 ± 1.5–29.6 ± 4.6 μM. The binding properties of H-BrQ and a model complex 1 to DNA were investigated by various methods. Results indicated that these lanthanide complexes interacted with DNA more strongly than free quinolinoline with intercalation being the most probable binding mode for both the complexes and quinolinoline.