The ConPET Mechanism Remains Veiled: Reply to "Unlocking the ConPeT Mechanism"

In this journal, a Correspondence by Ventura, Cozzi, and Ceroni reported time-resolved absorption spectroscopy studies in the electron transfer process from cyanoarene photocatalyst 3,4,5,6-tetrakis(diphenyl amino)phthalonitrile (4DPAPN) in the presence of tetrabutylammonium oxalate (TBAOx). This was used as a model reaction to investigate the mechanism of consecutive photoinduced electron transfer (ConPET) in our previously reported asymmetric [3+2] photocycloaddition. They proposed a new electron transfer pathway in which the electron from the excited state of the radical anion 4DPAPN*^•- solvated in acetonitrile. This article replies to their Correspondence, including: the experimental and theoretical analysis on the driving force of electron transfer and a series of new experiments conducted with purer reagents under more stringent conditions, which suggest that the process of proton-coupled electron transfer (PCET) followed by ConPET cannot be excluded, as proposed in our previous publication. Yet, Ceroni et al.'s efforts to study organic photochemical reactions using time-resolved spectroscopy remain worthwhile, and their proposed mechanism also led us to consider other possible pathways for the reaction. This article concludes with a series of constructive suggestions for further studying the ConPET mechanism using time-resolved absorption spectroscopy and other techniques.