New unsymmetrical μ -phenoxo bridged binuclear copper(II) complexes

Abstract

A series of binuclear Cu II complexes [Cu 2 XL] n + having two copper(II) ions bridged by different motifs (X = OH − , MeCO 2 − , or Cl − ) have been prepared using the ligands: H 2 L 1 = 4-methyl-2-[ N -(2-{dimethylamino}ethyl- N ′-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H 2 L 2 = 4-nitro-2-[ N -(2-{dimethylamino}ethyl- N ′-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H 2 L 3 = 4-methyl-2-[ N -(2-{diethylamino}ethyl- N ′-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H 2 L 4 = 4-nitro-2-[ N -(2-{diethylamino}ethyl- N ′-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol. The complexes have been characterized by spectroscopic, analytical, magnetic and electrochemical measurements. Cryomagnetic investigations (80–300 K) revealed anti-ferromagnetic exchange between the Cu II ions (−2 J in the range −50 to −182 cm −1 ). The strength of anti-ferromagnetic coupling lies in the order: OAc > OH > Cl. Cyclic voltammetry revealed the presence of two redox couples, assigned to Cu II /Cu II /Cu II /Cu I /Cu I /Cu I . The first reduction potential is sensitive to electronic effects from the aromatic ring substituents and steric effect on the donor nitrogens (side arm) of the ligand systems.