Synthesis and spectroscopic studies of some new redox-active benzylamine complexes of copper(II) and ESR studies of their oxidation-reduction products

New Cu(II) complexes Cu(L-x')(2), where L-x' = L-1', L-2', L-3', L-4' are m onoanion of unsubstituted, 5-Cl, 5-Br and 3,5-di-Br-substituted 2-hydroxybe nzylamines of redox-active N-(3,5-di-tert-butyl-1-hydroxyphenyl)-2-hydroxyb enzylamines were synthesized. Each compound of L-x'H and Cu(L-x')(2) as wel l as products of their oxidation and reduction by PbO2 and PPh3, respective ly, was characterized by IR, UV-visible and ESR spectroscopy. ESR results s howed that one-electron oxidation of mononuclear tetrahedrally distorted Cu (L-x')(2) chelates with PbO2, via C-C coupling of the Cu(II)-stabilized lig and radical intermediates and by the oxidative dehydrogenation of amine-che lates, produce new Cu(II) complexes with square-planar geometry. The powder ESR spectra of these new Cu(II) complexes exhibit a triplet-state type pat tern with the zero-field splitting due to interaction between the copper(II ) pairs. Interaction of Cu(L-x')(2) with PPh3 via intramolecular ligand-met al electron transfer results in the formation of radical species and reduct ion of the metal center, All radical intermediates were characterized by ES R parameters.