Electrochemical Remote Control for Dithienylethene-Ferrocene Switches

Abstract

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.

Fast and Efficient Oxidative Cycloreversion Reaction of a π‐Extended Photochromic Terarylene

“…Chemical or electrochemical oxidation has attracted attention as an alternative route for the ring‐opening reaction of diarylethenes because it proceeds with high efficiency in an (electro)catalytic manner . The efficiency of the electrocatalytic cycloreversion reaction was first quantitatively estimated for a dithiazolylthiazole (Scheme ; R 1 =R 2 =Me) to be more than 900 % as a net efficiency, and the instantaneous current efficiency reached over 2000 % as a result of the chain reaction shown in Scheme .…”

Photochromic Diarylethenes Designed for Surface Deposition: From Self‐Assembled Monolayers to Single Molecules

“…However, the high photocyclization quantum yield comes at a cost of low cycloreversion. Nevertheless, other strategies for cycloreversion are also available: heating, multi‐photon absorption, triplet sensitization, and photo/electrocatalytic chain reactions . Fourth, Irie and Uchida reported a diarylethene based on a benzothiophene where the aromatic groups have high fatigue resistance .…”

Why Are Dithienylethene‐Linked Biscobaltocenes so Hard to Photoswitch?

“…In the last three decades, hundreds of derivatives of those photochromic systems have been published: symmetrically and nonsymmetrically substituted ones, with different aromatic rings connected by cycloalkenes of different sizes and different organic and organometallic substituents . Their reversible photoswitching behaviour has been studied in solution, in the crystalline state, in liquid‐crystals and as gel .…”