Crystal structure, biological studies of water-soluble rare earth metal complexes with an ofloxacin derivative

Two new water-soluble solid complexes [PrL (NO3)2(CH3OH)] (NO3), [NdL(NO3)2(CH3OH)](NO3)(L = 9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperaziny)-7-oxo-7H-pyrido [1,2,3-de]-1,4-benzoxazine-6-carbaldehyde benzoyl hydrazone) have been synthesized by the reaction of Ln(III) nitrate with an ofloxacin derivative. The crystal structures of [PrL(NO3)2(CH3OH)](NO3) and [NdL(NO3)2(CH3OH)](NO3) were determined by single-crystal X-ray diffraction. The interactions of the ligand and Ln(III) complexes with calf thymus DNA (CT DNA) have been investigated by UV–Vis (UV–Vis) spectra, ethidium bromide (EB) displacement experiments, circular dichroism (CD) spectra, cyclic voltammetry (CV) and viscosity measurements. Experimental results indicated that Ln(III) complexes and ligand could bind to CT DNA via the intercalation mode and that the binding affinities of Ln(III) complexes are higher than that of free ligand. In addition, Ln(III) complexes could cleave pBR322 DNA in the presence and the absence of reductant. The free ligand did not show any DNA-cleaving abilities. Furthermore, the antioxidant activity of the ligand and Ln(III) complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro, which indicate that the Ln(III) complexes exhibit more effective antioxidant activity than the ligand alone.