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 NO₂X (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 H₂L have been used. The ligands H₂L yielded three binuclear [L₂Cu2II] 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⋯Cu distance and Cu-O(Ph)-Cu angle.