Induction of Cell Death by Ternary Copper(II) Complexes of l-Tyrosine and Diimines: Role of Coligands on DNA Binding and Cleavage and Anticancer Activity

The mononuclear mixed ligand copper(II) complexes of the type [Cu(l-tyr)(diimine)](ClO4), where tyr is l-tyrosine and diimine is 2,2′-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), 5,6-dimethyl-1,10-phenanthroline (5,6-dmp) (3), and dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq) (4), have been isolated and characterized by analytical and spectral methods. In the X-ray crystal structure 3 Cu(II) possesses a distorted square pyramidal coordination geometry with the two nitrogen atoms of 5,6-dmp ligand and the amine nitrogen and carboxylate oxygen atoms of l-tyrosine located at the equatorial sites and the coordinated water molecule present in the apical position. The electronic absorption and electron paramagnetic resonance (EPR) spectral parameters reveal that the complexes retain their square-based geometries even in solution. All of the complexes display a ligand field band in the visible region (600−700 nm) in Tris−HCl/NaCl buffer (5:50 mM) at pH 7.2 and also axial EPR spectra in acetonitrile at 77 K w...