DNA‐Binding Study of Nickel(II) and Zinc(II) Complexes with Two Novel Chromenone‐Based Schiff‐Base Ligands

Abstract

Abstractmagnified imageTwo new chromenone‐based Schiff‐base ligands, 3‐{[(1,5‐dihydro‐3‐methyl‐5‐thioxo‐4H‐1,2,4‐triazol‐4‐yl)imino]methyl}‐6‐hydroxy‐4H‐1‐benzopyran‐4‐one (L1) and 2,2′‐bis[(6‐hydroxy‐4‐oxo‐4H‐1‐benzopyran‐3‐yl)methylene]carbonothioic dihydrazide (L2), and their NiII and ZnII complexes were prepared. All the complexes were characterized by elemental analysis, IR data, and molar conductivity. The binding of these four complexes to calf‐thymus DNA was carefully investigated by UV/VIS spectroscopy, fluorescence spectroscopy, viscosity measurements, and CD spectra. The experimental results indicate that the four complexes bind to calf‐thymus DNA in an intercalative mode, with the intrinsic binding constants (K) of 3.94⋅104 ([NiL1]), 5.15⋅103 ([ZnL1]), 4.12⋅104 ([NiL2]), and 3.75⋅104 M−1 ([ZnL2]). These data show that the complexes of L2 can interact more strongly with DNA than complexes of L1, and the NiII complexes have a higher binding constant than ZnII complexes.