Electrochemical properties of some gold(III) complexes with (S,S)-R(2)edda-type ligands

Abstract

Oxidation-reduction properties of eleven gold(III) complexes with (S,S)-R(2)edda-type ligands was studied by cyclic and differential pulse voltammetry in DMSO. Series I: [AuCl2{(S,S)-R(2)eddip}]PF6, (S,S)-eddip = (S,S)-ethylenediamine-N,N'-di-2-propanoate, R = n-butyl, n-pentyl, isobutyl, isoamyl, cyclopentyl, 1-5; II: [AuCl2{(S,S)-R(2)eddch}]PF6, (S,S)-eddch = (S,S)-ethylenediamine-N,N'-di-2-(3-cyclohexyl)propanoate, R = methyl, ethyl, n-propyl, n-butyl, isobutyl, isoamyl, 6-11. Voltammograms in DMSO showed two successive irreversible reduction steps, where Au-I species were the final reduction product. Reduction potential values are in range from 116 to 156 mV (Ep(1)) and -520 to -572 mV (Ep(2)) for Series I and from 148 to 228 mV (Ep(1)) and -569 to -638 mV (Ep(2)) for Series II. In general, slightly easier reduction of complexes belonging to Series I (higher cytotoxicity) could be due to less steric hindrance around the gold center. Reduction potentials and anticancer activity are not in correlation.