Spectroscopic and electron-transfer reactivity studies of bulky bis(N-cycloalky1-3,5-Bu-t(2)-salicylaldiminato)copper(II) complexes: Generation of uncoordinated and coordinated phenoxyl radicals

Abstract

This work summarizes the results of our studies on the spectral, magnetic, electrochemical and chemical redox properties of N-cycloalkyl-3,5-Bu-t(2)-salicylaldimine ligands [cycloalkyl = cyclo-C5H9(HL1), cyclo-C6H11 (HL2), cyclo-C7H13 (HL3), cyclo-C8H15 (HL4), 1-adamantyl (HL5), 2-adamantyl (HL6)] and their copper(II) complexes (1-6). The compounds have been characterized by IR, H-1 NMR, UV-vis, EPR spectroscopy, electrochemical and magnetic susceptibility measurements. The geometry of 1-6, according to their EPR (g(parallel to) and g(parallel to)/A(parallel to)) and visible spectral data, exhibit a significant amount distortion from slightly distorted square-planar to pseudo-tetrahedral. The cyclic voltammetric studies of 1-6 reveal that as the extent of the tetrahedral distortion of Cu-II center increases on going from 1 to 5, the values of Cu-II/Cu-I potentials became more negative. The compounds have been oxidized electrochemically and chemically and the generated relatively stable uncoordinated phenoxyl [HLx](center dot+) and coordinated Cu(II)-phenoxyl radical [1-6](center dot+) species have been characterized by UV/vis and EPR spectroscopy. (C) 2010 Elsevier B.V. All rights reserved.