Exchange dynamics of redox-active self-assembling mixed monolayers

The exchange dynamics as well as the desorption and displacement reactions of redox-active self-assembling monolayers based on transition-metal complexes of osmium and ruthenium have been studied. On the basis of results from the above-mentioned processes, it appears that the exchange dynamics are controlled by the rate of desorption via a dissociative mechanism. We have also made use of wave-shape analysis in terms of shifts in the formal potentials and widths of the voltammetric waves with changes in the surface coverage and monolayer composition. The presence of mixed monolayers (Os/Ru) results in an increased broadening of the voltammetric wave associated with the ruthenium complex relative to the case of a monolayer of the ruthenium complex alone which we ascribe to an enhanced degree of electrostatic repulsion. Also based on an analysis of the voltammetric response, we believe that the mixed monolayers are randomly distributed rather than being composed of discrete and separated phases.