Ultrafast transient absorption spectroelectrochemistry: femtosecond to nanosecond excited-state relaxation dynamics of the individual components of an anthraquinone redox couple.
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Authors
Turner, Matthew AP
Staniforth, Michael
Burriss, Adam
Robinson, Ben R
Publication Date
2022-01-05Journal Title
Chem Sci
ISSN
2041-6520
Publisher
Royal Society of Chemistry (RSC)
Volume
13
Issue
2
Pages
486-496
Type
Article
This Version
VoR
Physical Medium
Electronic-eCollection
Metadata
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Goia, S., Turner, M. A., Woolley, J. M., Horbury, M. D., Borrill, A. J., Tully, J. J., Cobb, S., et al. (2022). Ultrafast transient absorption spectroelectrochemistry: femtosecond to nanosecond excited-state relaxation dynamics of the individual components of an anthraquinone redox couple.. Chem Sci, 13 (2), 486-496. https://doi.org/10.1039/d1sc04993c
Abstract
Many photoactivated processes involve a change in oxidation state during the reaction pathway and formation of highly reactive photoactivated species. Isolating these reactive species and studying their early-stage femtosecond to nanosecond (fs-ns) photodynamics can be challenging. Here we introduce a combined ultrafast transient absorption-spectroelectrochemistry (TA-SEC) approach using freestanding boron doped diamond (BDD) mesh electrodes, which also extends the time domain of conventional spectrochemical measurements. The BDD electrodes offer a wide solvent window, low background currents, and a tuneable mesh size which minimises light scattering from the electrode itself. Importantly, reactive intermediates are generated electrochemically, via oxidation/reduction of the starting stable species, enabling their dynamic interrogation using ultrafast TA-SEC, through which the early stages of the photoinduced relaxation mechanisms are elucidated. As a model system, we investigate the ultrafast spectroscopy of both anthraquinone-2-sulfonate (AQS) and its less stable counterpart, anthrahydroquinone-2-sulfonate (AH2QS). This is achieved by generating AH2QS in situ from AQS via electrochemical means, whilst simultaneously probing the associated early-stage photoinduced dynamical processes. Using this approach we unravel the relaxation mechanisms occurring in the first 2.5 ns, following absorption of ultraviolet radiation; for AQS as an extension to previous studies, and for the first time for AH2QS. AQS relaxation occurs via formation of triplet states, with some of these states interacting with the buffered solution to form a transient species within approximately 600 ps. In contrast, all AH2QS undergoes excited-state single proton transfer with the buffered solution, resulting in formation of ground state AHQS- within approximately 150 ps.
Identifiers
External DOI: https://doi.org/10.1039/d1sc04993c
This record's URL: https://www.repository.cam.ac.uk/handle/1810/334569
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