Synthesis, spectroscopy, and electrochemistry of copper(II) complexes with N,N′-bis(3,5-di-t-butylsalicylideneimine) polymethylenediamine ligands

Article abstract of DOI:10.1016/j.saa.2004.03.037

Bulky salen CuL_x derived from aliphatic polymethylene diamines, H₂N-(CH₂)_x-NH₂, where n = 2-6, and 3,5-di-t-butylsalicylaldehyde (H₂L_x) and some corresponding tetrahydrosalan complexes (CuL′_x) have been synthesized and characterized by their IR, UV - vis absorption and EPR spectra, by magnetic moments and by cyclic voltammetry in acetonitrile (for H ₂L_x) and DMF (for CuL_x). Complexes CuL _x and CuL′_x are magnetically normal (μ_exp = 1.83-1.91 μ_B). EPR spectra CuL_x characterized by the axial g and A_Cu, tensors with g∥ > g⊥ and without ¹⁴N-shf resolution in CHCl₃/toluene at 300 and 150K. The CV studies on acetonitrile solutions of H₂L _x revealed a well-defined quasi-reversible redox wave at E _1/2 = 0.95-1.15 V versus Ag/AgCl but CV of the CuL_x complexes in DMF exhibit weak pronounced irreversible oxidation waves at E _pa¹, = 0.51 - 0.98 V and Ep_a¹ = 1.16 - 1.33 V attributable to metal centered Cu(II/III) and ligand centered CuL _x/CuL_x⁺ couples, respectively. A poorly defined wave was observed for the quasi-reversible reduction Cu(II)/Cu(I) at potentials less than - 1.0 V.