Redox Umpolung of Phenalenyl-Based Molecule Inside Water-Soluble Nanocages

Phenalenyl (PLY) is the smallest, odd alternant polycyclic hydrocarbon known for its magnetic, conducting, and electronic properties. Such material properties are based on the capability of PLY to act as an electron reservoir. PLY has recently emerged as a reductive catalyst, wherein both its ground and excited states can form long-lived radical anions, driving diverse reductive transformations. However, the rich electronic properties of the π-backbone in PLY systems have never been exploited for oxidative transformations. Here, we incarcerate PLY inside a water-soluble Pd₆L₄¹²⁺ nanocavity to provide the first transient absorption signature of PLY-radical cation under photoirradiation, acting as the electron donor instead of its electron acceptor properties; demonstrating redox-umpolung behavior. Photoexciting host-guest charge transfer states, we drive a single electron transfer from PLY to the nanocavity within ∼2 ps, while a solvent-assisted deprotonation of the radical cation within ∼80 ps generates a reactive, long-lived neutral radical (>2 ns). As a proof of concept, utilizing this redox-umpolung photochemistry of PLY, we demonstrate a direct route for the synthesis of aromatic nitriles in water. We envision that our findings will pave the way for advancing water-compatible catalysis using PLY-based molecules, leveraging the unique reactivity of open-shell organic systems.