Synthesis, structure and electrochemistry of a copper(II) complex with 1,2-di{o-[o-hydroxy(naphthylideneimino)]phenoxy}ethane

The title Schiff base ligand, H2L, and its complex [CuL] have been prepared and characterized by elemental analysis and i.r. spectroscopy. The electrochemical properties of the single crystal [CuL]·0.5C2H4Cl2have been investigated by cyclic voltammetry (c.v.). Upon scanning at negative and positive potentials, two reduction and two oxidation waves were observed at E1/20= −0.47 and −0.77 V and E1/20= 1.10 and 1.39 V, respectively. Two Kcomvalues for the reduction and oxidation process are 1.2×105and 8.0×104, respectively, and indicate that the deprotonated ligand, L, has the ability to stabilize the mixed valent states of both CuIICuIand CuIICuIII. The crystal structure has been solved by X-ray diffraction, with a final R= 0.0653. Wound around a copper atom, the effectively tetradentate chain ligand, L, coordinates only viaits two imino and two phenolate groups at both ends of the chain. The geometry, D2dsymmetry, is best described as trans'N2O2' square-planar with slight tetrahedral distortion. The reason, why the mononuclear [CuL] unit can display two c.v. waves in each process, has been explained on the basis of configuration interchange between mono- and dinuclear units in c.v. electrolyte solution.