Unusual Photoreaction of Triquinacene within Self‐Assembled Hosts

Triquinacene is a concave tricyclic hydrocarbon with diverse photoreactivity. In the cavity of an electron‐accepting molecular host, triquinacene was specifically photooxidized at the peripheral allylic position into an alcohol, 1‐hydroxytriquinacene, via guest‐to‐host electron transfer. The unusual reactivity stems from the extremely electron‐deficient triazine panel ligand of the host cage, which allows the cage to function as a good electron acceptor. Thus, self‐assembled coordination cages can serve not only as molecular‐sized reaction vessels but also function electronically as redox media. Dissolved molecular oxygen is indispensable for the photoreaction and immediately traps a photogenerated radical.