Electroactive Foldamers Endowed with Tetrathiafulvalene Units: From Highly Stable Single Helical Structures to Redox-Triggered Duplex Formation.

Preparing new smart receptors and materials through controlling foldamer assemblies constitutes an appealing strategy. In this context, the use of a redox input appears as a relevant tool to monitor the self-assembly process, provided a careful design of well-chosen electroactive units. Our research group previously showed how the single-to-double helix equilibrium of foldamers can be shifted thanks to redox processes. Aiming at generalizing this strategy and rationalizing our findings, we designed a long oligopyridine dicarboxamide strand bearing tetrathiafulvalene (TTF) units, which are connected on the periphery through short amide linkers. This design proved to have a dramatic impact on the supramolecular behavior of the foldamer, preventing the formation of double helices in the neutral state. Using a combination of electrochemical and spectroscopic measurements, we show that duplex formation can be triggered by oxidizing a foldamer that does not form double helices in the neutral state.