Photoelectrochemical C−H Activation Through a Quinacridone Dye Enabling Proton‐Coupled Electron Transfer. Issue 5 (5th January 2023)

• Record Type: Journal Article
• Authors: Yang, Yunshuo; Volpato, Giulia Alice; Rossin, Elena; Peruffo, Nicola; Tumbarello, Francesco; Nicoletti, Catia; Bonetto, Ruggero; Paoloni, Lorenzo; Umari, Paolo; Colusso, Elena; Dell'Amico, Luca; Berardi, Serena; Collini, Elisabetta; Caramori, Stefano; Agnoli, Stefano; Sartorel, Andrea
• Is Part Of: ChemSusChem. Volume 16:Issue 5(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-05
• Subjects: bond-dissociation free energy -- C−H activation -- dyes -- photoelectrochemistry -- proton-coupled electron transfer; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.202201980
• Languages: English
• ISSNs: 1864-5631

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), TiO2, and SnO2 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. Abstract : Do or dye : Photoelectrochemical activation of C−H bonds is carried out at a SnO2 electrode sensitized with a quinacridone dye (QNC), operating through a proton‐coupled electron transfer and photochemically generating a nitrogen based radical [bond‐dissociation free energy (BDFE)=80.5 kcal mol −1 ] capable of hydrogen atom abstraction from allylic and benzylic C−H groups.