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

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 [LnL2·(NO3)2]·NO3 [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 × 106 and 1.33 × 106 M−1 through fluorescence titration data, respectively. In addition, the suppression ratio for image and OHradical dot 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 OHradical dot than that of mannitol. It indicates that the complexes have the activity to suppress image and OHradical dot and exhibit more effective antioxidants than ligand alone.