Chiral and conductive viologen-based supramolecular gels exhibiting tunable charge-transfer properties

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 & PRIME;-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 adding ionic additives. Careful control of the formation of charge-transfer complexes between viologens and iodides has led to the formation of robust, transparent, conductive, and chiral gel. The gelation process, the properties of the gel, and the structure of the assemblies have been thoroughly investigated by UV-Vis and ECD spectroscopy, rheometry, bright-field microscopy, SAXS, AFM, electrochemical and impedance measurements. Robust, transparent, conductive, redox-active and chiral gels are obtained by self-assembly of a cholesterol-substituted 4,4 & PRIME;-bipyridinium. Self-organization gives chiral hollow core-shell cylinders of inner radius 5.2 nm and shell thickness 2.6 nm.

Automated summary

Redox-active conductive supramolecular gels involving highly ordered chiral assemblies of small organic molecules have been synthesized and characterized in this study. The gelation process and properties of the gels were thoroughly investigated, and it was found that the optical, rheological, and electrical properties of the gels can be tuned by adding ionic additives. The self-assembly process formed chiral hollow core-shell cylinders with specific dimensions.