Chiral and Conductive Viologen-based Supramolecular Gels Exhibiting Tunable Charge-Transfer Properties

Abstract

Redox-active conductive supramolecular gels involving highly ordered chiral assemblies of small organic molecules are very promising soft materials for many applications ranging from catalysis to electronics. However, combining all these properties in the same material has so far remained a difficult task. We now report the synthesis and detailed structural, rheological and electrical characterizations of supramolecular gels obtained by self-assembly of a dicationic low molecular weight gelator incorporating a redox-active 4,4’-bipyridinium unit. These molecules have been shown to self-assemble in pentanol to form chiral hollow core-shell cylinders eventually yielding dendritic clusters inducing gelation. We also showed that the optical, rheological and electrical properties of the gels can be tuned by addition of ionic additives. Careful control of the formation of charge-transfer complexes between viologens and iodides have led to a robust, transparent, conductive and chiral gel. The gelation process and the structure/properties of the gel have been thoroughly investigated by UV-Vis and ECD spectroscopy, rheology, bright-field microscopy, SAXS, AFM, electrochemical and impedance measurements.