Electrochemical remote control for dithienylethene-ferrocene switches

The electrochromic properties of dithienylethene derivates is a field of great importance and interest. In this manuscript we describe a potential molecular remote control system, which can be electrochemically triggered. Diferrocenyl compounds containing a diethylenene photoelectrochromic core with perhydro- and perfluorocyclopentene ring were prepared in order to induce a change in the chromic properties via an intramolecular electron-transfer reaction from the redox group to the photochromic core. The electrochemical behavior of open and closed isomers was thoroughly studied using photochemical, electrochemical, and spectroelectrochemical techniques. The first redox couple was typically assigned to the ferrocene for the open isomer. However, for the closed isomer, an electrocatalytic ring-opening process was observed for the perhydrocyclopentene ring, while a slightly different electrochemical process was observed for the perfluorocyclopentene system. Mechanistic investigations revealed that an internal charge transfer is necessary to destabilize the closed bridge. Once opened, the bridge's cation radical is a strong oxidant, and the charge eventually gets localized on the ferrocene, The charges then migrate throughout the solution by self-exchange reactions. Hence, the redox status of the Fc units triggers the photochrom's reactivity playing the role of "antenna" that can temporarily store a charge and facilitate the transformation. This way to perform the transformation, i.e., by electrochemistry rather than photochemistry, presents the great advantage of being much more local and, thus, would permit the ultimate stage of miniaturization at the scale of just one molecule. © 2007 American Chemical Society.