DNA Cleavage by Copper Complexes of 2‐ and 3‐Clip‐Phen Derivatives

Abstract

Abstract The DNA cleavage activity of copper complexes of phenanthroline has been increased by the use of “2‐Clip‐Phen” and “3‐Clip‐Phen” ligands containing two phenanthroline entities linked by a serinol bridge. In order to optimize DNA cleavage activity, two series of new Clip‐Phen ligands (L) with two phenanthroline residues linked through their C‐2 or C‐3 carbon atoms by different bridges have been synthesized. The physicochemical properties and the DNA cleavage activities of the corresponding (Clip‐Phen)copper complexes were investigated in the presence of a reductant and air. X‐ray analyses of single crystals showed that the cupric complexes of Clip‐Phen were able adopt dimeric double‐helical geometries with L 2 Cu 2 stoichiometries in the solid state. These complexes adopt different geometries and stoichiometries in solution, with monomeric LCu species predominant. The compounds with a bridge connected at C‐2 are less active as DNA cleavage agents than complexes with the bridge at the C‐3 positions. Copper complexes with a bridge containing three methylene units appear to give the best results in DNA cleavage experiments. This activity is increased in the case of 3‐Clip‐Phen·CuCl 2 by the presence of the primary amine function of the serinol bridge. This amine function is probably coordinated to the copper atom in the case of 2‐Clip‐Phen·CuCl 2 , decreasing the reactivity toward DNA. (© Wiley‐VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)