Copper(II) complexes with tripodal imidazole-containing ligands. Structure-electrochemistry relationship

Abstract

Mono- and dimeric copper(II) complexes of tris- (benzimidazol-2-ylmethyl)amine (L 1) and of its derivatives with the imidazole NH protons substituted by a methyl (L 2), ethyl (L 3), benzyl (L 4) or o-methylbenzyl (L 5) group were prepared and characterized based on magnetic susceptibility, conductivity, cyclic voltammetric half-wave potential ( E 1 2 ), infrared, electronic and ESR spectra. The complexes containing H 2O, NO 3 −, Cl −, Br −, N 3 −, and N-methylimidazole with L 1–L 5 were mononuclear copper(II) complexes, while the complexes with NCS − or NCO − and L 1–L 3 [except [Cu(L 1)NCS](NO 3)] were dinuclear ones, which dissociate to monomeric complexes in DMF solution. The E 1 2 values of copper(II) in a series of complexes containing H 2O or NO 3 − decrease in the order L 5 > L 1 > L 2 > L 3 > L 4, whereas those in complexes with Br − and N-methylimidazole decrease in the orders L 4 ≳ L 5 > L 1 > L 2 > L 3 and L 5 > L 1 > L 4 ≳ L 2 > L 3, respectively. The relationship between the structure of the complexes and the E 1 2 values are discussed in some detail.