Visible light-mediated C (sp3)-H bond functionalization inside an all-organic nanocavity

Ultrafast C-H bond activation and functionalization in confinement using visible light will enable engineering chemical reactions with extraordinary speed and selectivity. To provide a transition metal-free route, here we demonstrate C-H bond activation reactions on poly-aromatic hydrocarbons (PAH) in all-organic cationic nanocage ExBox(4+) for the first time. Visible light excitation in the host-guest charge transfer (CT) state allows the formation of oxidized photoproducts with high selectivity. Mechanistic understanding of this CT-mediated photoreaction using femtosecond broadband transient absorption revealed a few similar to 100 ps timescale for C-H bond breaking on the attached -CH3 group via sequential electron transfer and proton transfer steps. We envision that our photosensitizer-free method will open up new avenues to pursue organic reactions using cavities that could serve both as photoredox catalysts and hosts for reactive reaction intermediates.

Automated summary

Ultrafast C-H bond activation and functionalization in confinement using visible light is demonstrated for the first time on poly-aromatic hydrocarbons (PAH) using an all-organic cationic nanocage. This transition metal-free method allows the formation of oxidized photoproducts with high selectivity through host-guest charge transfer. The mechanism involves sequential electron transfer and proton transfer steps with a timescale of a few hundred picoseconds.