Journal article
Solvent-dependent photochemical dynamics of a phenoxazine-based photoredox catalyst
Zeitschrift für physikalische Chemie (Neue Folge), Vol.234(7), pp.1475-1494
08/27/2020
DOI: 10.1515/zpch-2020-1624
Abstract
Organic substitutes for ruthenium and iridium complexes are increasingly finding applications in chemical syntheses involving photoredox catalysis. However, the performance of these organic compounds as electron-transfer photocatalysts depends on their accessible photochemical pathways and excited state lifetimes. Here, the UV-induced dynamics of N-phenyl phenoxazine, chosen as a prototypical N-aryl phenoxazine organic photoredox catalyst, are explored in three solvents, N,N-dimethyl formamide, dichloromethane and toluene, using ultrafast transient absorption spectroscopy. Quantum chemistry calculations reveal the locally excited or charge-transfer electronic character of the excited states, and are used to assign the transient electronic and vibrational bands observed. In toluene-d
, complete ground-state recovery is (31 ± 3) % by internal conversion (IC) from the photo-excited state (or from S
after IC but before complete vibrational relaxation), (13 ± 2) % via direct decay from vibrationally relaxed S
(most likely radiative decay, with an estimated radiative lifetime of 13 ns) and (56 ± 3) % via the T
state (with intersystem crossing (ISC) rate coefficient
= (3.3 ± 0.2) × 10
s
). In dichloromethane, we find evidence for excited state N-phenyl phenoxazine reaction with the solvent. Excited state lifetimes, ISC rates, and ground-state recovery show only modest variation with changes to the solvent environment because of the locally excited character of the S
and T
states.
Details
- Title: Subtitle
- Solvent-dependent photochemical dynamics of a phenoxazine-based photoredox catalyst
- Creators
- Mahima Sneha - School of Chemistry, University of Bristol, Cantock’s Close, BS 1TS, Bristol, UKLuke Lewis-Borrell - School of Chemistry, University of Bristol, Cantock’s Close, BS 1TS, Bristol, UKDarya Shchepanovska - School of Chemistry, University of Bristol, Cantock’s Close, BS 1TS, Bristol, UKAditi Bhattacherjee - School of Chemistry, University of Bristol, Cantock’s Close, BS 1TS, Bristol, UKJasper Tyler - School of Chemistry, University of Bristol, Cantock’s Close, BS 1TS, Bristol, UKAndrew J Orr-Ewing - School of Chemistry, University of Bristol, Cantock’s Close, BS 1TS, Bristol, UK
- Resource Type
- Journal article
- Publication Details
- Zeitschrift für physikalische Chemie (Neue Folge), Vol.234(7), pp.1475-1494
- DOI
- 10.1515/zpch-2020-1624
- ISSN
- 0942-9352
- eISSN
- 2196-7156
- Publisher
- De Gruyter
- Number of pages
- 20
- Grant note
- 290966 / ERC EP/L015366/1 / EPSRC EP/R012695/1 / EPSRC EP/L015722/1 / EPSRC 793799 / EU Marie-Sklodowska Curie Fellowship
- Language
- English
- Date published
- 08/27/2020
- Academic Unit
- Chemistry
- Record Identifier
- 9984216671702771
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