LAUSR

Abstract New heteroleptic complexes having the general formula (N^N)MQCl, where N^N = 2,2′-bipyridine or 1,10-phenanthroline, M = Cu(II) or Zn(II) and Q = quercetin were synthesized and characterized by analytical and spectroscopic methods. The complexes are more sensitive to air oxygen in solution or solid state than their flavonoid ligand. The increased sensitivity towards oxidation of the metal complexes was evidenced in the solid state by TGA-DTA measurements and in solution by UV–Vis absorption. The Zn(II) heteroleptic derivatives are luminescent in solution, their emission maxima being red-shifted with respect to quercetin precursor. The free radical scavenging activity of the complexes was evaluated using the stable DPPH radical. Cu(II) heteroleptic complexes have higher antioxidant activity than the Zn(II) complexes. Different oxidative mechanisms were evidenced for the Cu(II) and Zn(II) heteroleptic complexes.