Synthesis, spectroscopic characterization and EPR studies on electron transfer reactions of bis[ N-(2,5-di- tert-butylphenyl)salicylaldiminato]copper complexes with PPh 3

Abstract

New bidentate N-(2,5-di- tert-butylphenyl)salicylaldimines bearing X=H, HO, CH 3O, Br, NO 2, 3,5-di-Br, 3-NO 2-5-Br and 5,6-benzo substituents on the salicylaldehyde moiety, L x H, 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, 1H NMR, ESR spectroscopy, magnetic measurements, as well as reactions of Cu(L x ) 2 with PPh 3 were studied. It has been found that some complexes with X=HO and CH 3O unlike their electron-withdrawing and unsubstituted analogues are readily reduced by PPh 3 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 63,65Cu, 31P, 14N nuclei and aromatic protons.