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On the mechanism of phenolate photo-oxidation in aqueous solution.

Tyson, Alexandra L. and Verlet, Jan R. R. (2019) 'On the mechanism of phenolate photo-oxidation in aqueous solution.', Journal of physical chemistry B., 123 (10). pp. 2373-2379.

Abstract

The photo-oxidation dynamics following ultraviolet (257 nm) excitation of the phenolate anion in aqueous solution is studied using broadband (550–950 nm) transient absorption spectroscopy. A clear signature from electron ejection is observed on a sub-picosecond timescale, followed by cooling dynamics and the decay of the signal to a constant offset that is assigned to the hydrated electron. The dynamics are compared to the charge-transfer-to-solvent dynamics from iodide at the same excitation wavelength and are shown to be very similar to these. This is in stark contrast to a previous study on the phenolate anion excited at 266 nm, in which electron emission was observed over longer timescales. We account for the differences using a simple Marcus picture for electron emission in which the electron tunneling rate depends sensitively on the initial excitation energy. After electron emission, a contact pair is formed which undergoes geminate recombination and dissociation to form the free hydrated electron at rates that are slightly faster than those for the iodide system. Our results show that, although the underlying chemical physics of electron emission differs between iodide and phenolate, the observed dynamics can appear very similar.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1021/acs.jpcb.8b11766
Publisher statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in the Journal of physical chemistry B copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcb.8b11766
Date accepted:No date available
Date deposited:06 March 2019
Date of first online publication:15 February 2019
Date first made open access:15 February 2020

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