Transition metal complexes of asymmetrical aroyl-hydrazone ligand: Syntheses, structures, DNA binding and cleavage studies

Syntheses and crystal structures of aroyl-hydrazone ligands and their transition metal complexes (E)-N′-(2-hydroxybenzylidene)-1-methyl-4-nitro-1H-pyrrole-2-carbohydrazide (H21), [CuII(H1)Cl] (2), [FeIII(H1)Cl2(MeOH)] (3), [MnIII(1)(μ-OMe)(MeOH)]2 (4), [VVO(1)(OMe)] (5), Et3NH[VVO2(1)] (6), [CoII(H1)(μ-Cl)(H2O)]2 (7) and [CoII(1)2] (7′) are reported in this paper. The binding abilities of the compounds with calf thymus DNA are measured by using UV–Vis and fluorescence spectra. The apparent binding constant (Kobs = (1.66 ± 0.21) × 104 M−1) and rate constant (kobs = 3.62 ± 0.17 h−1) of 2 with CT-DNA is calculated, respectively. The quenching constants (Kq) 3.52 × 104 for 3, 1.97 × 104 for 4, 5.94 × 103 for 2, 3.32 × 103 for 7, 1.64 × 103 for 5, 1.55 × 103 M−1 for H21 are determined, respectively, using ethidium bromide, as fluorescence probe. Agarose gel electrophoresis studies indicated that the complexes cleave plasmid pBR322 DNA by a hydrolytic mechanism.