Influence of aggregation on redox potentials of amphiphilic Cu(II) complexes modeled after bleomycin antibiotics

The influence of micellization on the redox potential of a series of three amphiphilic Cu(II) complexes was investigated by comparing their electrochemical properties on glassy carbon (GC) with those observed for the corresponding nonsurfactant models. The ligands examined were modeled after the metal-binding site of the antibiotic bleomycin (BLM). Comparison with the BLM-Cu(II) complex showed similar electrochemical behavior for the nonsurfactant complexes. The E_1/2 values were assessed by cyclic voltammetry and Osteryoung square wave voltammetry and found to correlate with the structure of the complexes. The amphiphilic Cu(II) complexes displayed a significant positive shift (in the range 100-120 mV) with respect to their nonsurfactant models. Investigation of the electrochemistry of the copper complexes of both surfactant and nonsurfactant complexes in the presence of neutral (Triton-100), cationic (CTABr), and anionic (SDS) cosurfactants at concentrations below and above their cmc allowed us to differentiate between the electrostatic and hydrophobic contributions to the shift of the redox potentials.