Spectroscopic and Electron-Transfer Reactivity Studies of Bulky Bis(n-Cycloalkyl) 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-tBu<inf>2</inf>-salicylaldimine ligands [cycloalkyl = cyclo-C<inf>5</inf>H<inf>9</inf>(HL<inf>1</inf>), cyclo-C<inf>6</inf>H<inf>11</inf> (HL<inf>2</inf>), cyclo-C<inf>7</inf>H<inf>13</inf> (HL<inf>3</inf>), cyclo-C<inf>8</inf>H<inf>15</inf> (HL<inf>4</inf>), 1-adamantyl (HL<inf>5</inf>), 2-adamantyl (HL<inf>6</inf>)] and their copper(II) complexes (1-6). The compounds have been characterized by IR, 1H NMR, UV-vis, EPR spectroscopy, electrochemical and magnetic susceptibility measurements. The geometry of 1-6, according to their EPR (g<inf>II</inf> and g<inf>II</inf>/A<inf>II</inf>) 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 CuII center increases on going from 1 to 5, the values of CuII/CuI potentials became more negative. The compounds have been oxidized electrochemically and chemically and the generated relatively stable uncoordinated phenoxyl [HL<inf>x</inf>]{radical dot}+ and coordinated Cu(II)-phenoxyl radical [1-6]{radical dot}+ species have been characterized by UV/vis and EPR spectroscopy. © 2010 Elsevier B.V. All rights reserved.