Photoelectrochemical C−H Activation Through a Quinacridone Dye Enabling Proton‐Coupled Electron Transfer
Yunshuo Yang, Giulia Alice Volpato, Elena Rossin, Nicola Peruffo, Francesco Tumbarello, Catia Nicoletti, Ruggero Bonetto, Lorenzo Paoloni, Paolo Umari, Elena Colusso, Luca Dell’Amico, Serena Berardi, Elisabetta Collini, Stefano Caramori, Stefano Agnoli, Andrea Sartorel
Abstract
Abstract Dye‐sensitized photoanodes for C−H activation in organic substrates are assembled by vacuum sublimation of a commercially available quinacridone (QNC) dye in the form of nanosized rods onto fluorine‐doped tin oxide (FTO), TiO 2 , and SnO 2 slides. The photoanodes display extended absorption in the visible range (450–600 nm) and ultrafast photoinduced electron injection (<1 ps, as revealed by transient absorption spectroscopy) of the QNC dye into the semiconductor. The proton‐coupled electron‐transfer reactivity of QNC is exploited for generating a nitrogen‐based radical as its oxidized form, which is competent in C−H bond activation. The key reactivity parameter is the bond‐dissociation free energy (BDFE) associated with the N⋅/N−H couple in QNC of 80.5±2.3 kcal mol −1 , which enables hydrogen atom abstraction from allylic or benzylic C−H moieties. A photoelectrochemical response is indeed observed for organic substrates characterized by C−H bonds with BDFE below the 80.5 kcal mol −1 threshold, such as γ‐terpinene, xanthene, or dihydroanthracene. This work provides a rational, mechanistically oriented route to the design of dye‐sensitized photoelectrodes for selective organic transformations.