Fe(II) Complexes Containing Bioactive Ligands: Synthesis, DNA Binding, and Cleavage Studies

The two Fe(II) complexes of fused aromatic N and S containing ligands of the type [Fe(HMq)3] (PF6)2 [complex (1)] and [Fe(HSeq)3] (PF6)2 [complex (2)] (where HMq = 2-mercapto-4-methylquinoline and HSeq = 2-seleno-4-methylquinoline) were synthesized and structurally characterized. The DNA binding property of the complexes with calf thymus DNA has been investigated using absorption spectra, viscosity measurements, as well as thermal denaturation experiments. Intrinsic binding constant Kb has been estimated at room temperature. The absorption spectral studies indicate that the complexes intercalate between the base pairs of the CT-DNA tightly with intrinsic DNA binding constant of 1.9 x 106 M-1 for complex (1) and 2.5 x 106 M-1 for complex (2) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2, respectively. Detailed analysis revealed that the metal complexes intercalates into the DNA base stack as intercalator. The oxidative cleavage activity of the complexes (1) and (2) were studied by using gel electrophoresis and the results show that complexes have potent nuclease activity.