Modulating Electron Transfer in an Organic Reaction via Chemical Group Modification of the Photocatalyst

Tuning electron-transfer (ET) rates from catalysts to substrates is important for modulating photocatalytic organic reactions. In this work, we have taken pyrene-based photocatalysts (Py's) for photocatalytic hydrodefluorination of polyfluoroarenes (FAs) as model systems and conducted a first-principles study on modulating ET rates from Py to FA via the chemical modification of Py with different electron-donating/withdrawing groups (EDGs/EWGs). The computed spatial distributions of frontier Kohn-Sham orbitals suggest that ET is energetically more favorable for Py-EDGs than for Py-EWGs. The estimated ET rates by a simplified Marcus model show that they are appreciably enhanced by EDG substitution and weakened by EWG substitution. Noticeably, the associated Gibbs free-energy change plays a dominant role. Our findings of tuning ET rates for Py-FA complexes via chemical group modifications cast new insight into the rational design of metal-free photocatalysts for organic transformations.