Synthesis, spectroscopic and redox properties of a novel series of copper(II) complexes of N-alkyl-3,5-But2-salicylaldimines.: Generation of the directly coordinated Cu(II)-phenoxyl radical complexes

A series of novel copper(II) complexes, X, with N-R-3,5-Bu-2'-salicylaldimines, derived from 3,5-Bu-2'-salicylaldehyde and alkyl-amines (RNH2) have been prepared and their spectroscopic (IR, UV-Vis, ESR), magnetic and redox reactivity are described. ESR spectral parameters and mu(eff) values suggest that complexes are magnetically diluted in the solid state. The CV of some X exhibits a dependence of Cu-II/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 (NH4)(2)Ce(NO3)(6) in CHCl3 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 Cu-II 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. (c) 2005 Elsevier Ltd. All rights reserved.