Synthesis, spectroscopic characterization and EPR studies on electron transfer reactions of bis[N-(2,5-di-tert-butylphenyl)salicylaldiminato]copper complexes with PPh3

Abstract

New bidentate N-(2,5-di-tert-butylphenyl)salicylaidimines bearing X = H, HO, CH3O, Br, NO2, 3,5-di-Br, 3-NO2-5-Br and 5,6-benzo substituents on the salicylaldchyde moiety, (LH)-H-x, and their mononuclear bis[N-(2,5-di-tert-butylphenyl)salicylaldiminato]copper(II) complexes, Cu(L-x)(2), have been prepared and investigated by IR, UV-Visible, H-1 NMR, ESR spectroscopy, magnetic measurements, as well as reactions of Cu(L-x)(2) with PPh3 were studied. It has been found that some complexes with X = HO and CH3O unlike their electron-withdrawing and unsubstituted analogues are readily reduced by PPh3 via intramolecular electron transfer from ligand to copper(II) to give Cu-stabilized radical intermediates. The spectra of the primary radicals interpreted in terms of couplings of unpaired electron with Cu-63,Cu-65, (31)p, N-14 nuclei and aromatic protons. (C) 2002 Elsevier Science B.V. All rights reserved.