CLAY MODIFIED ELECTRODES .10. STUDIES OF CLAY-ADSORBED RU(BPY)32+ ENANTIOMERS BY UV-VISIBLE SPECTROSCOPY AND CYCLIC VOLTAMMETRY

The difference of a factor of 2 found in the values of ct the total concentration of adsorbed cation, between racemic Ru(bpy)3Cl2 and its enantiomers in clay modified electrodes, is attributed to differences in the effect of the adsorption of the cations on the degree of aggregation of the clays. UV-visible spectra indicate less aggregation of the clays upon addition of the enantiomers than the racemate, leaving more exposed surface for the adsorption of the ion pairs. This lower layering explains why the clays were found to adsorb twice their CEC (cation exchange capacity) for the enantiomers, but only their CEC for racemic Ru(bpy)2+3, in contradiction to previous results with Ru(phen)2+3, where it was the racemate that was reported to be adsorbed in excess of the CEC. Despite the differences in the values of ct, similar peak currents were found in the cyclic voltammograms of racemic Ru(bpy)2+3 and its enantiomers in clay modified electrodes, since a smaller fraction of the adsorbed enantiomers were found to be electroactive. The decrease in currents due to this lower fraction more than makes up for their larger ct. © 1990.