Effect of adenine moiety on DNA binding property of copper(ii)–terpyridine complexes

Abstract

Two novel copper(II) terpyridine complexes, [Cu(atpy)(NO₃)(H₂O)](NO₃)·3H₂O (1) and [Cu(ttpy)(NO₃)₂] (2) (atpy = 4′-p-N9-adeninylmethylphenyl-2,2′:6,2″-terpyridine; ttpy = 4′-p-tolyl-2,2′:6,2″-terpyridine) have been prepared and structurally characterized by X-ray crystallography. Both complexes show a CuN₃O₂ coordination in a square pyramidal (4 + 1) geometry with terpyridine acting as an equatorial ligand. For complex 1, intermolecular AA base pairing interaction is observed between N⁶ and N¹ of adjacent adenines with N⁶⋯N¹ of 3.027(7) Å. A molecular dynamics simulation of the DNA binding of two complexes showed that the adenine moiety plays an important role in the intercalation of 1 into DNA. This is verified by UV, fluorescence, circular dichroism and flow linear dichroism studies. The promotional effect from the adenine moiety to the intracellular DNA binding of complex 1 is also confirmed by the inductively coupled plasma mass (ICP-MS) spectrometry data which showed a significant higher copper content in DNA isolated from complex 1 treated MCF-7 and HeLa cells.