A Redox-Active Heterocyclic Capsule: Radical Generation, Oxygenation, and Guest Uptake/Release.

For the development of a redox-active supramolecular capsule with host function, we synthesized a bent heterocyclic amphiphile using phenothiazine panels capable of adopting three different states, i.e., neutral, radical, and oxygenated states. In water, the new amphiphiles spontaneously and quantitatively assemble into a heterocycle-based capsule with an average diameter of ∼2 nm, through the hydrophobic effect and π-stacking interactions. The product structure was confirmed by the combination of NMR, UV-visible, DLS, AFM, and molecular modeling studies. Electrochemical and chemical oxidation of the capsule generates relatively stable radical cation capsules at room temperature in a reversible fashion. The neutral capsule efficiently takes up large hydrophobic compounds (e.g., pigment blue 15 and fullerene C) into the heterocyclic cavity through a grinding protocol and subsequent chemical oxidation of the products generates radical host-guest complexes. Moreover, chemical oxygenation of the host-guest complexes was shown to induce guest release in water via disassembly of the capsular structure through dioxygenation of the phenothiazine panels.