DNA-binding and anti-oxidation properties of binuclear lanthanide(III) complexes of 8-hydroxyquinoline-7-carbaldehyde-(isonicotinyl)hydrazone

Binuclear complexes [LnL(NO3)(H2O)(2)](2) were prepared from the Schiff base 8-hydroxyquinoline-7-carbaldehyde-(isonicotinyl)hydrazone (H2L) and equivalent molar amounts of Ln(NO3)(3)center dot 6H(2)O (Ln = La3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Ho3+, Er3+, Yb3+), respectively. The ligand is dibasic tetradentate and the dimerization occurs through the phenolate oxygen atoms leading to a central four-membered (LnO)(2)-ring. The ligand and all the Ln(III) complexes can bind to calf thymus DNA through intercalation with binding constants of 10(5)-10(6) (mol L-1)(-1), and they show strong scavenging abilities on hydroxyl radicals and superoxide radicals. The values of SC50 of Ln(III) complexes for HO center dot and O-2(-center dot) are 2.344-13.33 and 4.459-28.48 mu mol L-1, respectively. Ln(III) complexes present stronger binding abilities to DNA and stronger anti-oxidation properties than ligand. Complex containing hydroxyl unit shows stronger scavenging abilities on hydroxyl radical, while complex containing N-heteroaromatic substituent shows stronger scavenging abilities on superoxide radicals. Furthermore, earlier rare metal complexes show stronger scavenging abilities on both hydroxyl radicals and superoxide radicals.