Das Neves Rodrigues, Natercia, Staniforth, Michael, Young, Jamie D., Peperstraete, Yoann, Cole-Filipiak, Neil Charles, Gord, Joseph, Walsh, Patrick Sullivan, Hewett, Daniel, Zwier, Timothy S. and Stavros, Vasilios G. (2016) FDDYNAM16 Towards elucidating the photochemistry of the sunscreen filter ethyl ferulate using time-resolved gas-phase spectroscopy. Faraday Discussions, 194 . pp. 709-729. doi:10.1039/C6FD00079G ISSN 0301-7249.

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Abstract

Ultrafast time-resolved ion yield (TR-IY) and velocity map imaging spectroscopies are employed to reveal the relaxation dynamics after photoexcitation in ethyl 4-hydroxy-3-methoxycinnamate (ethyl ferulate, EF), an active ingredient in commercially available sunscreens. In keeping with a bottom-up strategy, the building blocks of EF, 2-methoxy-4-vinylphenol (MVP) and 4-hydroxy-3-methoxycinnamyl alcohol (coniferyl alcohol, ConA), were also studied to assist in our understanding of the dynamics of EF as we build up in molecular complexity. In contrast to the excited state dynamics of MVP and ConA, which are described by a single time constant (>900 ps), the dynamics of EF are described by three time constants (15 ± 4 ps, 148 ± 47 ps, and >900 ps). A mechanism is proposed involving internal conversion (IC) between the initially excited S1(11ππ*) and S2(11nπ*) states followed by intramolecular vibrational redistribution (IVR) on both states, in competition with intersystem crossing onto neighbouring triplet states (15 ± 4 ps). IVR and IC within the triplet manifold then ensues (148 ± 47 ps) to populate a low-lying triplet state (>900 ps). Importantly, the fluorescence spectrum of EF at the S1 origin, along with the associated lifetime (6.9 ± 0.1 ns), suggests that population is trapped, during initial IVR, on the S1(11ππ*) state. This serves to demonstrate the complex, competing dynamics in this sunscreen filter molecule.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Science > Chemistry
Journal or Publication Title:	Faraday Discussions
Publisher:	Royal Society of Chemistry
ISSN:	0301-7249
Official Date:	1 December 2016
Dates:	Date Event 1 December 2016 Published 28 April 2016 Available 28 April 2016 Accepted 13 April 2016 Submitted
Volume:	194
Page Range:	pp. 709-729
DOI:	10.1039/C6FD00079G
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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