Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates

Luke Lewis-Borrell; Mahima Sneha; Aditi Bhattacherjee; Ian P Clark; Andrew J Orr-Ewing

doi:10.1039/D0SC01194K

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Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates

Journal article

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Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates

Luke Lewis-Borrell, Mahima Sneha, Aditi Bhattacherjee, Ian P Clark and Andrew J Orr-Ewing

Chemical science (Cambridge), Vol.11(17), pp.4475-4481

05/06/2020

DOI: 10.1039/D0SC01194K

PMCID: PMC8159429

PMID: 34122905

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Abstract

The rapid development of new applications of photoredox catalysis has so far outpaced the mechanistic studies important for rational design of new classes of catalysts. Here, we report the use of ultrafast transient absorption spectroscopic methods to reveal both mechanistic and kinetic details of multiple sequential steps involved in an organocatalyzed atom transfer radical polymerization reaction. The polymerization system studied involves a N,N-diaryl dihydrophenazine photocatalyst, a radical initiator (methyl 2-bromopropionate) and a monomer (isoprene). Time-resolved spectroscopic measurements spanning sub-picosecond to microseconds (i.e., almost 8 orders of magnitude of time) track the formation and loss of key reactive intermediates. These measurements identify both the excited state of the photocatalyst responsible for electron transfer and the radical intermediates participating in propagation reactions, as well as quantifying their lifetimes. The outcomes connect the properties of N,N-diaryl dihydrophenazine organic photocatalysts with the rates of sequential steps in the catalytic cycle.

Details

Title: Subtitle: Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates
Creators: Luke Lewis-Borrell - School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Mahima Sneha - School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Aditi Bhattacherjee - School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Ian P Clark - Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Oxfordshire, UK
Andrew J Orr-Ewing - School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
Resource Type: Journal article
Publication Details: Chemical science (Cambridge), Vol.11(17), pp.4475-4481
DOI: 10.1039/D0SC01194K
PMID: 34122905
PMCID: PMC8159429
NLM abbreviation: Chem Sci
ISSN: 2041-6520
eISSN: 2041-6539
Grant note: DOI: 10.13039/100010663, name: H2020 European Research Council, award: 793799; DOI: 10.13039/501100000266, name: Engineering and Physical Sciences Research Council, award: EP/L015366/1, EP/R012695/1; DOI: 10.13039/100011199, name: FP7 Ideas: European Research Council, award: 290966
Language: English
Date published: 05/06/2020
Academic Unit: Chemistry
Record Identifier: 9984216615002771

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