Exchange experiments utilizing Ru(bpy)(2)(4,4'-(CO2H)(2)bpy)(2+) and Os(bpy)(2)(4,4'-(CO2H)(2)bpy)(2+) (4,4'-(CO2H)(2)bpy is 4,4'-dicarboxy-2,2'-bipyridine) provide evidence for a distribution of binding sites on ITO electrodes by electrochemical monitoring and on optically transparent, nanoparticle TiO2 films by optical monitoring. Using the Albery model of dispersed kinetics for the analysis of exchange, the results are consistent with dissociative loss from the surface with k(1) = 0.1 s(-1) for the dissociative step in CH3CN on ITO. Equilibrium binding data after exchange suggest that a site or distribution of sites is also present that undergoes exchange on a very slow time scale. Complete exchange takes place in EtOH, and the rate is greatly enhanced compared to that in CH3CN, suggesting that EtOH labilizes the surface to exchange. On TiO2 the time scale for exchange is far longer than that on ITO, and in CH3CN it scales with film thickness.