Synthesis, characterization, and reactivity of copper complexes supported by the TPMEN ligand framework

Abstract

Two new Cu(II) complexes supported by nitrogen-rich ligands have been synthesized and characterized by absorption spectroscopy, magnetic moment, and cyclic voltammetry. Complex 1 is supported by the ligand TPMEN (N,N,N′-tris(2-pyridylmethyl)-N′-methylethylenediamine) with two amine and three pyridyl nitrogen donors; while 2 is supported by the ligand TQMEN (N,N,N′-tris(2-quinolylmethyl)-N′-methylethylenediamine) where quinoline groups replace the pyridyl groups. Replacing the pyridyl moiety with quinoline has a marked effect on the Cu(II/I) reduction couple. The complexes are capable of reducing superoxide (O2−) to hydrogen peroxide (H2O2) in the presence of a proton donor. The reaction between potassium superoxide (KO2) and the Cu-complexes was monitored via absorption spectroscopy, and further probed with electrospray ionization mass spectrometry (ESI-MS). Both 1 and 2 depicted evidence of ligand oxidation in mass-spectrometry.