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

Abstract

A series of binuclear Cu II complexes [Cu2XL] nþ having two copper(II) ions bridged by different motifs (X = OH � , MeCO � ,o r Cl � ) have been prepared using the ligands: H2L 1 ¼ 4-methyl-2-[N-(2-{dimethylamino}ethyl-N¢methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H2L 2 ¼ 4-nitro-2-[N-(2-{dimethylamino}ethyl-N¢-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H2L 3 ¼ 4-methyl-2-[N-(2-{diethylamino}ethyl-N¢-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H2L 4 ¼ 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 (� 2J 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.