Reversible Electron-responsive Self-Assembly of a Supramolecular Gel Network

Redox-active supramolecular gels involving highly ordered assemblies of small organic molecules are very promising soft materials for many applications ranging from catalysis to electronics. These materials however mostly rely on the use of chemical fuels, making their reversibility intrinsically limited. Even though the use of electrochemical stimulation could greatly improve the reversibility of redox-responsive systems it still remains mostly unexplored due to major scientific and technical bottlenecks. We now report the electron-responsiveness of a supramolecular gel obtained through the chiral self-assembly of a low molecular weight gelator derived from 4,4-bipyridinium salts (viologens). The reduction of the viologen-based gels was achieved using photochemical and electrochemical stimulation. The link between the sample composition and microstructure upon reduction of viologen moieties have been thoroughly investigated using both in operando bright microscopy and absorption spectroscopy measurements. We showed that the system electron-responsiveness is based on the association/dissociation of charge transfer complexes. We also showed that different strategies can be used to efficiently stimulate the viologen moieties which are entrapped in the gel 2 supramolecular network. Both the dissolution and reformation of the viologen-based supramolecular network could be achieved through electrochemical stimulation. We consequently report here one of the very first systems able to undergo a reversible electrochemically induced supramolecular polymerization.