A copper(II) complex of the Schiff base from l-valine and 2-hydroxy-1-naphthalidene plus 1,10-phenanthroline: synthesis, crystal structure, and DNA interaction

A new Cu(II) complex, [Cu(naph-val)phen] (naph-val = Schiff base derived from 2-hydroxy-1-naphthaldehyde and l-valine, phen = 1,10-phenanthroline), has been synthesized and characterized by physicochemical methods. The crystal structure of the complex showed that there are four independent molecular structures in the crystallographic asymmetric unit, and each of them shows a distorted square-pyramidal CuN₃O₂ coordination geometry. In the crystal, the π − π stacking and intermolecular hydrogen bonds form a 2D network. The interactions between the Cu(II) complex and calf thymus DNA (CT-DNA) have been studied by spectroscopic methods, as well as viscosity and thermal denaturation measurements. The results indicate that the Cu(II) complex binds to CT-DNA in an intercalative mode. The cleavage reaction on pBR322 plasmid DNA has been investigated by agarose gel electrophoresis in the absence and presence of mercaptopropionic acid. The Cu(II) complex exhibits an efficient DNA cleavage activity.