Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights

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

doi:10.1038/s41467-019-13154-w

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Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights

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Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights

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

Nature communications, Vol.10(1), pp.5152-7

11/13/2019

DOI: 10.1038/s41467-019-13154-w

PMCID: PMC6853971

PMID: 31723133

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Abstract

The photochemical decarboxylation of carboxylic acids is a versatile route to free radical intermediates for chemical synthesis. However, the sequential nature of this multi-step reaction renders the mechanism challenging to probe. Here, we employ a 100 kHz mid-infrared probe in a transient absorption spectroscopy experiment to track the decarboxylation of cyclohexanecarboxylic acid in acetonitrile-d over picosecond to millisecond timescales using a photooxidant pair (phenanthrene and 1,4-dicyanobenzene). Selective excitation of phenanthrene at 256 nm enables a diffusion-limited photoinduced electron transfer to 1,4-dicyanobenzene. A measured time offset in the rise of the CO byproduct reports on the lifetime (520 ± 120 ns) of a reactive carboxyl radical in solution, and spectroscopic observation of the carboxyl radical confirm its formation as a reaction intermediate. Precise clocking of the lifetimes of radicals generated in situ by an activated C-C bond fission will pave the way for improving the photocatalytic selectivity and turnover.

Details

Title: Subtitle: Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights
Creators: Aditi Bhattacherjee - AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands. a.bhattacherjee@amolf.nl
Mahima Sneha - School of Chemistry, University of Bristol, Cantocks Close, Bristol, BS8 1TS, UK
Luke Lewis-Borrell - School of Chemistry, University of Bristol, Cantocks Close, Bristol, BS8 1TS, UK
Omri Tau - School of Chemistry, University of Bristol, Cantocks Close, Bristol, BS8 1TS, UK
Ian P Clark - Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0QX, UK
Andrew J Orr-Ewing - School of Chemistry, University of Bristol, Cantocks Close, Bristol, BS8 1TS, UK. a.orr-ewing@bristol.ac.uk
Resource Type: Journal article
Publication Details: Nature communications, Vol.10(1), pp.5152-7
DOI: 10.1038/s41467-019-13154-w
PMID: 31723133
PMCID: PMC6853971
NLM abbreviation: Nat Commun
ISSN: 2041-1723
eISSN: 2041-1723
Language: English
Date published: 11/13/2019
Academic Unit: Chemistry
Record Identifier: 9984216602802771

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