Electrostatically Induced Isomerization of Azobenzene Derivatives in Langmuir−Blodgett Films

Abstract

A novel electrochemically induced cis-to-trans isomerization process involving amphiphilic azobenzene derivatives in Langmuir−Blodgett monolayer films at electrode/electrolyte interfaces was examined using electrochemical and UV−visible absorption measurements. This isomerization proceeds electrostatically, i.e., with no Faradaic current and no discernible features in the double-layer capacitive charging current, when relatively positive electrode potentials are applied to the monolayer film. This electrostatically induced process is rather slow (first-order rate constants in the 10-2−10-1 s-1 range over the potential range of +0.65 to +0.85 V vs Ag/AgCl, respectively), but the highest rate constant measured (at +0.85 V vs Ag/AgCl) represents an increase of approximately 3 orders of magnitude compared to that of the thermal isomerization process. Surprisingly, the activation energy for the electrostatic process was found to be essentially potential independent and nearly the same as that for thermal isome...