Periodic Reporting for period 1 - MARCUS (Mapping Reaction Pathways Using Transient Ultrafast Spectroscopies: Kinetic and Mechanistic Investigation of Photoredox Catalysed Reactions)
Reporting period: 2018-05-01 to 2020-04-30
The main objective of this project was to study the mechanistic and kinetic details of the modus operandi of these photocatalysts (PC) using laser based spectroscopic methods. A photoredox cycle involves multiple sequential steps from the ultrafast photoexcitation of the catalyst (10-15 seconds or femtoseconds) to the reaction completion and recovery of the PC which happens on much slower time scales (microseconds to milliseconds). Using ultrafast laser pulses (10-15 s) and experiments which spanned more than 10 orders of magnitude in time (femtoseconds to milliseconds), our objective was to probe each of these steps from start to completion, thereby revealing their role in controlling the catalytic process. To this end, using our laser facilities at the University of Bristol and at the Rutherford Appleton Laboratory, we have mechanistically investigated many different photoredox cycles. We were able to track several short-lived species, some previously unobserved, using time-resolved absorption spectroscopies. The outcomes from these studies have shed light on kinetic and mechanistic details in these reactions and have allowed us to refute or support the mechanisms proposed by synthetic chemists.
The results from these studies will benefit synthetic and theoretical chemists alike. While the understanding of the mechanistic pathways can help synthetic chemists in designing more robust catalysts, the high quality experimental spectroscopic data can greatly help computational chemists in building better theoretical models by comparing their predictions to our data.
The main objective of this project was to study the mechanistic details of photoredox catalyzed reactions using ultrafast transient spectroscopies. We have successfully investigated many photoredox reactions such as photoredox based controlled polymerizations, and the synthesis of smaller organic molecules using photoredox catalysis. The outcomes of these studies have been reported in three peer reviewed publications in high impact journals (such as Nature Communications, Chemical Science) so far and more are in preparation. These publications which are all open access are widely accessible and have led to further collaborations with international groups. These results were further disseminated to the wider scientific community through participation in conferences where the applicant presented a talk or poster. In addition to this, the European Researcher’s night in 2018 and 2019 was used as a platform to talk to the general public about the project and how important the fundamental understandings emerging through laser-based spectroscopies are in driving chemistry further.