Synthesis, crystal structure and DNA-binding studies of the Ln(III) complex with 6-hydroxychromone-3-carbaldehyde benzoyl hydrazone

A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand (L) and its Ln(III) complexes, [Ln = La(1) and Sm(2)], have been prepared and characterized. The crystal and molecular structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Antioxidative activity tests in vitro showed that L and its complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction and also oxygen free radicals, and that the effect of the La(III) complex I is stronger than that of mannitol and the other compounds. The compounds were tested against tumor cell lines including HL-60 and A-549. The data shows that the suppression rate of complexes I and 2 against the tested tumor cells are superior to the free ligand (L). The interactions of complexes I and 2, and L, with calf thymus DNA were investigated by UV-visible (UV-vis), fluorescence, denaturation experiments and viscosity measurements. Experimental results indicated that complexes 1 and 2, and L can bind to DNA via the intercalation mode, and that the binding affinity of complex I is higher than that of complex 2 and of free ligand (L). The intrinsic binding constants of complexes I and 2, and L were (7.62 +/- 0.56) x 10(6), ( 3.70 +/- 0.47) x 10(6) and (2.41 +/- 0.46) x 10(6) M-1, respectively. (C) 2007 Published by Elsevier Inc.