Mechanistic insights into two-photon-driven photocatalysis in organic synthesis. Issue 12 (8th March 2018)

• Record Type: Journal Article
• Authors: Marchini, Marianna; Gualandi, Andrea; Mengozzi, Luca; Franchi, Paola; Lucarini, Marco; Cozzi, Pier Giorgio; Balzani, Vincenzo; Ceroni, Paola
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 12(2018)
• Page Start: 8071
• Page End: 8076
• Publication Date: 2018-03-08
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp08011e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Is two-photon catalysis better than one-photon? The sequential absorption of two photons enables the production of highly reducing or oxidizing species. The short lifetime of the excited states and the photostability of the photocatalyst pose significant limitations to this approach. Abstract : A mechanism based on the sequential absorption of two photons by the components of a redox couple has been recently proposed for catalysis of the energetically demanding reduction of aryl halides. Here, we analyze the suggested photochemical mechanism of this reaction, which employs perylenediimide (PDI) as a photocatalyst, on the basis of spectroscopic, electrochemical and electron paramagnetic resonance data. Our results indicate that the photoexcited PDI radical anion (*PDI˙ − ) cannot play the role of a photosensitizer in the aforementioned process. Instead, the reduction of 4′-bromoacetophenone likely involves *PDI˙ − decomposition products. The extremely short lifetime of the photoexcited transient species, as *PDI˙ −, is a major general limitation for photocatalytic schemes based on sequential two-photon excitation. In order to better understand the potential of such schemes, we discuss them in the context of the Z-scheme in natural photosynthesis.