Ultrafast spectroscopy studies of photoredox catalysed reaction mechanismsUltrafast spectroscopy studies of photoredox catalysed reaction mechanisms
Lead Research Organisation:
University of Bristol
Department Name: Chemistry
Abstract
Many applications of chemistry use catalysis to enhance the rates and efficiencies of critical reaction steps, but refinement of catalyst design and development of new catalytic methods require a deep understanding of their mechanisms of reaction. Catalytic cycles are made up of a sequence of steps that can occur on timescales from femtosecond through to millisecond or longer, spanning more than 10 orders of magnitude of time. These individual steps involve reactive intermediates which can be difficult to isolate, but which must be identified for a complete understanding of the reaction mechanism. This research project will use advanced ultrafast spectroscopy techniques to observe the sequence of steps in photo-initiated catalytic cycles in solution, from catalyst activation on sub-picosecond timescales to completion of reactions. Transient features in infra-red and ultraviolet/visible absorption spectra will identify the intermediate species, measure the timescales for their production and loss, characterize solvent-solute interactions which influence catalyst performance at the molecular level, and build a comprehensive picture of complete catalytic pathways.
The research will focus on photoredox catalysis, which is transforming chemical synthesis. Photoredox catalysts use visible and near-UV light to initiate chemical transformations under mild conditions. Transient absorption spectroscopy measurements will seek to observe the complete cycle of steps from UV excitation of the photoredox catalyst to bimolecular radical reactions initiated by electron transfer, and ultimately to recovery of the catalyst. The outcomes will identify the properties of the molecular photocatalysts which control their performance, and will direct the optimized design of organic photocatalysts for sustainable future applications including the synthesis of molecules and materials with numerous medicinal and technological applications
The research will focus on photoredox catalysis, which is transforming chemical synthesis. Photoredox catalysts use visible and near-UV light to initiate chemical transformations under mild conditions. Transient absorption spectroscopy measurements will seek to observe the complete cycle of steps from UV excitation of the photoredox catalyst to bimolecular radical reactions initiated by electron transfer, and ultimately to recovery of the catalyst. The outcomes will identify the properties of the molecular photocatalysts which control their performance, and will direct the optimized design of organic photocatalysts for sustainable future applications including the synthesis of molecules and materials with numerous medicinal and technological applications
People |
ORCID iD |
| Andrew Orr-Ewing (Primary Supervisor) | |
| Georgia Thornton (Student) |
Publications
Thornton GL
(2021)
Transient absorption spectroscopy of the electron transfer step in the photochemically activated polymerizations of N-ethylcarbazole and 9-phenylcarbazole.
in Physical chemistry chemical physics : PCCP
| Description | My project has been based around studying photoredox reaction mechanisms with the use of ultrafast spectroscopic methods namely transient electronic/ vibrational absorption spectroscopy in the solution-phase. I have successfully studied the electron transfer step in the polymerization of N-ethylcarbazole and 9-phenylcarbazole in different environments by changing the solvent and electron acceptor present in the reaction. As a result, I have been able to determine how different components effect the efficiency of this reaction. This work has been published in PCCP. I have also studied the formation of alpha-tertiary amines with the same spectroscopic methods in a collaboration with the University of Bath. We have been able to successfully observe vital steps in the photocatalytic redox cycle and obtain information about the reaction steps to aid the synthesis of the molecules. The photocatalysts used in this synthesis are widely adopted in the synthetic community and furthering our understanding of these molecules is essential for academic progression in the scientific community. The work from this project is being written up for publication. The projects I have worked on have enabled me to learn laboratory skills which have been vital in the completion of my projects both at the University of Bristol and at the Rutherford Appleton Laboratory (RAL) at the Central Laser Facility (CLF). The data collected has been used to improve my analytical techniques and enabled me to apply complex fitting procedures to obtain more information about the data I collect. In development of the project, I have also improved my computational skills which are being used to further my understanding of the molecules and interactions occurring in my reaction mechanisms. |
| Exploitation Route | The information obtained from my projects will be beneficial to the scientific community because in depth insights into reaction mechanisms can aid many different sectors. Synthetic chemists will obtain a greater understanding on the way that carbazoles polymerize as well as how alpha-tertiary amines form in the absence of a protecting group. Obtaining information on the way that molecules react can enable other scientists to suggest modifications to the reaction mixture to improve efficiency of the reaction or to learn things about how similar molecules are formed. The information obtained also helps chemists understand the concentrations that can be used in reaction mixtures and how different concentrations can lead to different spectroscopic outcomes and hence, different reactions. The redox reaction of molecules is a strongly advancing field of science where lots of new information is being discovered. My project enables a cross over between the physical and organic sciences and enables new information to be learnt by multiple parties. Similar projects are being conducted by other members of my research group. All the information obtained by this field is furthering the development of academic research. |
| Sectors | Chemicals,Energy |
| Description | Observing the Photoredox Mechanism for the Formation of Alpha-Tertiary Amines with Transient Absorption Spectroscopy |
| Organisation | University of Bath |
| Department | Department of Chemistry |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Taking transient electronic and vibrational absorption spectroscopy measurements on the molecules provided by the University of Bath at the Rutherford Appleton Laboratory at the Central Laser Facility and at the University of Bristol in order to determine information about the reaction mechanism occurring. As well as this steady state data was recorded to aid these measurements. The data was analyzed by myself and my research team and the information is being prepared to be written up for publication. All efforts on this project have been shared by members of the research team. |
| Collaborator Contribution | The collaborating team provided the molecules and chemicals required for the study of this reaction mechanism as well as came up with the proposed mechanism of action for the redox reaction. They have provided constant communication about the progress they have made in synthesizing the molecules as well as the factors that have improved or hindered the reaction. They have also provided information on how to alter the project for spectroscopic study to factor in any limitations we have. |
| Impact | In the process of preparing for publication. |
| Start Year | 2019 |