“π-Hole−π” Interaction Promoted Photocatalytic Hydrodefluorination via Inner-Sphere Electron Transfer

We
describe a metal-free, photocatalytic hydrodefluorination (HDF)
of polyfluoroarenes (FA) using pyrene-based photocatalysts (Py). The
weak “π-hole−π” interaction between
Py and FA promotes the electron transfer against unfavorable energetics
(ΔGET up to 0.63 eV) and initiates
the subsequent HDF. The steric hindrance of Py and FA largely dictates
the HDF reaction rate, pointing to an inner-sphere electron transfer
pathway. This work highlights the importance of the size and shape
of the photocatalyst and the substrate in controlling the electron
transfer mechanism and rates as well as the overall photocatalytic
processes.