Synthesis, spectroscopic and redox properties of the copper(II) complexes of N-(di-methylphenyl)-3,5-Bu2t-salicylaldimines

A series of copper(II) complexes (CuL2x) with new N-di-methylphenyl-3,5-Bu2t-salicylaldimines (LxH) were prepared and characterized by IR, UV/vis, 1H NMR, ESR, cyclic voltammetry techniques and chemical oxidation. LxH ligands have been found selectively bind to a CuII, rather than to NiII, CoII, MnII, VOIV, ZnII and CdII. ESR examinations of the CuL2x complexes demonstrate that they exist in magnetically diluted mononuclear or coupled triplet-state structures in the solid. The temperature dependent (113-283 K) intensity of the powder ESR spectra for some CuL2x is characteristic of ferromagnetic coupling (J > 0). The reduction potentials of CuL2x in DMSO are sensitive to aniline moieties. Chemical oxidation of CuL2x with (NH4)2[Ce(NO3)6] in CHCl3 and MeCN solutions at 300 K affords gradually disappearance of their ESR signals and dramatic changes in the electronic spectra as well as the appearance of new maximum bands at 530-672 (CHCl3) and 670-700 nm (MeCN), suggesting generation of CuII-phenoxyl radical species.