Synthesis,characterisation,in vitro DNA binding properties and antioxidant activities of Ln(III) complexes with chromone-3-carbaldehyde-(2′-hydroxy) benzoyl hydrazone

Ln(III) complexes with chromone-3-carbaldehyde-(2′-hydroxy)benzoyl hydrazone as the Schiff base ligand have been synthesised and characterised by elemental analysis, molar conductivity, ¹H NMR, mass spectra, UV–Vis spectra, and IR spectra. Electronic absorption spectra, fluorescence spectra, ethidium bromide displacement experiments and viscosity measurements indicate that the free ligand and its Ln(III) complexes, especially the La(III) complex, bind strongly to calf thymus DNA via an intercalation mechanism. The intrinsic binding constants of the free ligand, La(III) complex, Sm(III) complex and Er(III) complex with DNA were (2.20±0.12) x 10⁵ M⁻¹, (8.83±0.04) x 10⁶ M⁻¹, (7.35±0.07) x 10⁶ M⁻¹ and (3.24±0.04) x 10⁶ M⁻¹, respectively. Furthermore, the antioxidant activity of the ligand and its Ln(III) complexes was determined by the superoxide and hydroxyl radical scavenging method in vitro, which indicates that the ligand and its Ln(III) complexes are efficient antioxidants and the Ln(III) complexes exhibit more effective antioxidant activity than the free ligand alone and some standard antioxidants, such as mannitol and vitamin C.