Synthesis, Characterization and Redox Behavior of bis(N-1-Adamantanyl- and N-2-Adamantanyl-3,5-tBu2-Salicylaldiminato)Copper(II) Complexes

Abstract

Two new bulky ligands, N-(1-adamantyl)-3,5-tBu<inf>2</inf>-salicylaldimine (1), and N-(2-adamantyl)-3,5-tBu<inf>2</inf>-salicylaldimine (2), and their copper bis-chelate complexes, 3 and 4, have been prepared and their analytical, spectroscopic and magnetic properties, chemical and electrochemical redox reactivity are described. EPR and UV/Vis results [higher g<inf>∥</inf>/A<inf>∥</inf>, lower energy λ (nm)] for 3 and 4 suggest a distorted square planar geometry with a higher degree of distortion for 3 than for 4. Chemical oxidation of 1-4 by ACN, on the basis of their EPR and UV/Vis spectra results in the formation of the free 1{radical dot}+, 2{radical dot}+ phenoxyl and Cu(II)-phenoxyl radicals complexes [g = 2.0065 (3{radical dot}+), 2.0099 (4{radical dot}+) and λ<inf>max</inf> at ca. 430 and 720 nm]. Electrochemical studies have shown that the complexes possess ligand- and copper(II)-centered quasi-reversible and irreversible responses and the more distorted complex 3, having the bulkier 1-adamantyl on the imine nitrogen, was reduced at a more negative potential than the less distorted complex 4. © 2007 Elsevier Ltd. All rights reserved.