DNA binding and nuclease activity of copper(II) complexes of tridentate ligands

Two copper(II) complexes, 1 and 2 with L1 and L2 [L1 = 2-hydroxybenzyl(2-(pyridin-2-yl)ethylamine); L2 = 2-hydroxybenzyl(2-(pyridin-2-yl)methylamine)] ligands, respectively, have been synthesized and characterized. The interaction of both the complexes with DNA has been studied to explore their potential biological activity. The DNA binding properties of the complexes with calf thymus (CT) DNA were studied by spectroscopic titration. The complexes show binding affinity to CT DNA with binding constant (Kb) values in the order of 105 M−1. Thermal denaturation and circular dichroism studies suggest groove binding of the complexes to CT DNA. Complexes also exhibit strong DNA cleavage activity in presence of reducing agents like 3-mercaptopropionic acid and β-mercaptoethanol. Mechanistic studies reveal the involvement of reactive hydroxyl radicals for their DNA cleavage activity.