Synthesis, characterization, and DNA-binding properties of the Ln(III) complexes with 6-hydroxy chromone-3-carbaldehyde-(2′-hydroxy) benzoyl hydrazone

Abstract

A new ligand, 6-hydroxy chromone-3-carbaldehyde-(2′-hydroxy) benzoyl hydrazone (L), was prepared by condensation of 6-hydroxy-3-carbaldehyde chromone (CDC) with 2-hydroxy benzoyl hydrazine. Its four rare earth complexes have been synthesized and characterized on the basis of elemental analyses, molar conductivities, mass spectra, 1H NMR, thermogravimetry/differential thermal analysis (TG–DTA), UV–vis spectra, fluorescence spectra, and IR spectra. The general formula of the complexes is [LnL 2·(NO 3) 2]·NO 3 [Ln = La( 1), Sm( 2), Dy( 3), Eu( 4)]. Spectrometric titration, ethidium bromide displacement experiments, and viscosity measurements indicate that Eu(III) complex and ligand, especially the Eu(III) complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constants of Eu(III) complex and ligand with DNA were 3.55 × 10 6 and 1.33 × 10 6 M −1 through fluorescence titration data, respectively. In addition, the suppression ratio for O 2 − and OH of the ligand and its complexes was studied by spectrophotometric methods. The experimental results show that La ( 1), Sm ( 2), and Eu ( 4) complexes are better effective inhibitor for OH than that of mannitol. It indicates that the complexes have the activity to suppress O 2 − and OH and exhibit more effective antioxidants than ligand alone.