Synthesis, Spectroscopic and Redox Properties of a Novel Series of Copper(II) Complexes of N-Alkyl Generation of the Directly Coordinated Cu(II)-Phenoxyl Radical Complexes

Abstract

A series of novel copper(II) complexes, X, with N-R-3,5-Bu2t- salicylaldimines, derived from 3,5-Bu2t-salicylaldehyde and alkylamines (RNH<inf>2</inf>) have been prepared and their spectroscopic (IR, UV-Vis, ESR), magnetic and redox reactivity are described. ESR spectral parameters and μ<inf>eff</inf> values suggest that complexes are magnetically diluted in the solid state. The CV of some X exhibits a dependence of CuII/Cu I potentials on bulkiness R groups, but the ligand centered oxidation potentials are less influenced by the nature of R. In the chemical oxidation of X with 8-10-fold excess (NH<inf>4</inf>)<inf>2</inf>Ce(NO<inf>3</inf>) <inf>6</inf> in CHCl<inf>3</inf> at 300 K, besides decreasing ESR signal of X, the appearance of a new broad lines centered at ca. g = 2.116-2.217 and radical signals (g = 2.0048 - 2.0086) assigned to new CuII centers and Cu(II)-phenoxyl radicals, respectively, were detected. UV-Vis spectra revealed new maxima at 630-790 nm for all oxidized X complexes and a very weak shoulder at ca. 800-830 nm for some of them. © 2005 Elsevier Ltd. All rights reserved.