Synthesis, characterization and redox behavior of bis(N-1-adamantanyl- and N-2-adamantanyl-3,5-tBu2-salicylaldiminato)copper(II) complexes

Two new bulky ligands, N-(1-adamantyl)-3,5-tBu2-salicylaldimine (1), and N-(2-adamantyl)-3,5-tBu2-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∥/A∥, 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+, 2+ phenoxyl and Cu(II)-phenoxyl radicals complexes [g = 2.0065 (3+), 2.0099 (4+) and λmax 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.

The synthesis, spectroscopic (1H NMR, IR, UV/Vis, EPR), chemical and electrochemical redox behaviors of two new bis(N-1-adamantanyl and 2-adamantanyl-3,5-tBu2-salicylaldiminato)copper(II) complexes (3 and 4) are described. EPR and UV/Vis results suggest that the chemical oxidation of the ligands and their complexes with (NH4)2Ce(NO3)6 results in the generation of the free phenoxyl and Cu(II)-phenoxyl radicals. The more tetrahedrally distorted 3 was reduced at a more negative potential than the less distorted 4.Figure optionsDownload as PowerPoint slide