Synthesis, ESR, UV-Visible and Reactivity Studies of New Bis(n-Dimethoxyaniline Copper(II) Complexes

Abstract

Several new copper(II) complexes (4-6) with N-dimethoxyphenyl-3,5- tBu<inf>2</inf>-salicylaldimine ligands abbreviated as N-R-3,5-DTBS, where R = 2,4-dimethoxyphenyl (1), 2,5-dimethoxyphenyl (2) and 3,5-dimethoxyphenyl (3) have been prepared and their spectroscopic (IR, 1H NMR, UV/Vis, ESR), magnetic and redox reactivity are described. The ESR spectra of frozen-solution 4-6 and solid state 4 and 5 are indicative of axially symmetric g-tensor (g<inf>∥</inf> > g<inf>⊥</inf> > 2.03). The powder ESR spectrum of 6 is unusual for CuN<inf>2</inf>O<inf>2</inf> type systems and exhibits "reversed" type (g<inf>∥</inf> < g<inf>⊥</inf>) signal with a rhombic g-tensor g<inf>3</inf> (2.235) > g<inf>2</inf> (2.128) > g<inf>1</inf> (2.019) pattern indicative of a dz2 ground state. Chemical oxidation of 4 and 6, as supported by ESR and UV/Vis techniques, generates new Cu(II) species and Cu(II)-phenoxyl radicals. The CV studies have shown that the complexes possess ligand-centered and copper(II)-centered quasi-reversible and irreversible responses. © 2012 Elsevier B.V. All rights reserved.