Synthesis, crystal structure, magnetic and redox properties of Cu(II)-Cu(II) binuclear complexes of bis(phenol) amine ligands

Copper(II) complexes of a series of tripodal ligands containing two phenolate moieties and NO(2)X (X = S or O donor ligands) coordination sphere were synthesized: N,N-bis(3,5-di-tert-butyl-2-hydroxybenzyl)2-(aminomethyl) furan, N,N-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-2-(methoxyethylamine) and newly synthesized N,N-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-2-(aminomethyl) thiophene H(2)L have been used. The ligands H(2)L yielded three binuclear [L(2)Cu(2)(II)] complexes, which have been characterized by X-ray crystallography, UV-Vis and magnetic susceptibility measurements. The phenolate moieties of the copper complexes were electrochemically oxidized to phenoxyl radicals. The ferro- and antiferromagnetic exchange coupling of two copper centers of these complexes have been investigated by magnetic susceptibility (2-290 K) measurements. A weaker antiferromagnetic coupling is found in copper complex with methoxy arm, and a weaker ferromagnetic coupling has been observed in two other complexes with furan and thiophene arms, compared to other phenoxo-bridged dicopper(II) complexes. The weak exchange coupling constants (J) of these complexes, when compared to the literature values, is most likely attributed to the smaller Cu center dot center dot center dot Cu distance and Cu-O(Ph)-Cu angle. (C) 2010 Elsevier Ltd. All rights reserved.