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

摘要

The title Schiff base ligand, H_2L, and its comples [CuL] have been prepared and characterized by elemental analysis and i.r. spectroscopy. The electrochemical properties of the single crystal [CuL]·0.5C_2H_4Cl_2 have been investigated by cyclic voltammery (c.v.). Upon sacanning at negative and positive potentials, two reduction and two oxidation waves were observed at E_(1/2)~O = -0.47 and -0.77 V and E_(1/2)~O = 1.10 and 1.39 V, respectively. Two K_(com) values for the reduction and oxidation process are 1.2 x 10~5 and 8.0 x 10~4, respectively, and indicate that the deprotonated ligand, L, has the ability to stabilize the mixed valent state of both Cu~(II)Cu~I and Cu~(II)Cu~(III). 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 via its imino and two phenolate groups at both ends of the chain. The geometry, D_(2d) symmetry, is best described as trans 'N_2O_2' 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 dinulcear units in c.v. electrolyte solution.