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Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone

[Image: see text] Avobenzone (AB) is a widely used UVA filter known to undergo irreversible photodegradation. Here, we investigate the detailed pathways by which AB photodegrades by applying UV laser-interfaced mass spectrometry to protonated AB ions. Gas-phase infrared multiple-photon dissociation...

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Autores principales: Berenbeim, Jacob A., Wong, Natalie G. K., Cockett, Martin C. R., Berden, Giel, Oomens, Jos, Rijs, Anouk M., Dessent, Caroline E. H.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2020
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7168606/
https://www.ncbi.nlm.nih.gov/pubmed/32208697
http://dx.doi.org/10.1021/acs.jpca.0c01295
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author Berenbeim, Jacob A.
Wong, Natalie G. K.
Cockett, Martin C. R.
Berden, Giel
Oomens, Jos
Rijs, Anouk M.
Dessent, Caroline E. H.
author_facet Berenbeim, Jacob A.
Wong, Natalie G. K.
Cockett, Martin C. R.
Berden, Giel
Oomens, Jos
Rijs, Anouk M.
Dessent, Caroline E. H.
author_sort Berenbeim, Jacob A.
collection PubMed
description [Image: see text] Avobenzone (AB) is a widely used UVA filter known to undergo irreversible photodegradation. Here, we investigate the detailed pathways by which AB photodegrades by applying UV laser-interfaced mass spectrometry to protonated AB ions. Gas-phase infrared multiple-photon dissociation (IRMPD) spectra obtained with the free electron laser for infrared experiments, FELIX, (600–1800 cm(–1)) are also presented to confirm the geometric structures. The UV gas-phase absorption spectrum (2.5–5 eV) of protonated AB contains bands that correspond to selective excitation of either the enol or diketo forms, allowing us to probe the resulting, tautomer-dependent photochemistry. Numerous photofragments (i.e., photodegradants) are directly identified for the first time, with m/z 135 and 161 dominating, and m/z 146 and 177 also appearing prominently. Analysis of the production spectra of these photofragments reveals that that strong enol to keto photoisomerism is occurring, and that protonation significantly disrupts the stability of the enol (UVA active) tautomer. Close comparison of fragment ion yields with the TD-DFT-calculated absorption spectra give detailed information on the location and identity of the dissociative excited state surfaces, and thus provide new insight into the photodegradation pathways of avobenzone, and photoisomerization of the wider class of β-diketone containing molecules.
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spelling pubmed-71686062020-04-21 Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone Berenbeim, Jacob A. Wong, Natalie G. K. Cockett, Martin C. R. Berden, Giel Oomens, Jos Rijs, Anouk M. Dessent, Caroline E. H. J Phys Chem A [Image: see text] Avobenzone (AB) is a widely used UVA filter known to undergo irreversible photodegradation. Here, we investigate the detailed pathways by which AB photodegrades by applying UV laser-interfaced mass spectrometry to protonated AB ions. Gas-phase infrared multiple-photon dissociation (IRMPD) spectra obtained with the free electron laser for infrared experiments, FELIX, (600–1800 cm(–1)) are also presented to confirm the geometric structures. The UV gas-phase absorption spectrum (2.5–5 eV) of protonated AB contains bands that correspond to selective excitation of either the enol or diketo forms, allowing us to probe the resulting, tautomer-dependent photochemistry. Numerous photofragments (i.e., photodegradants) are directly identified for the first time, with m/z 135 and 161 dominating, and m/z 146 and 177 also appearing prominently. Analysis of the production spectra of these photofragments reveals that that strong enol to keto photoisomerism is occurring, and that protonation significantly disrupts the stability of the enol (UVA active) tautomer. Close comparison of fragment ion yields with the TD-DFT-calculated absorption spectra give detailed information on the location and identity of the dissociative excited state surfaces, and thus provide new insight into the photodegradation pathways of avobenzone, and photoisomerization of the wider class of β-diketone containing molecules. American Chemical Society 2020-03-25 2020-04-16 /pmc/articles/PMC7168606/ /pubmed/32208697 http://dx.doi.org/10.1021/acs.jpca.0c01295 Text en Copyright © 2020 American Chemical Society This is an open access article published under a Creative Commons Attribution (CC-BY) License (http://pubs.acs.org/page/policy/authorchoice_ccby_termsofuse.html) , which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
spellingShingle Berenbeim, Jacob A.
Wong, Natalie G. K.
Cockett, Martin C. R.
Berden, Giel
Oomens, Jos
Rijs, Anouk M.
Dessent, Caroline E. H.
Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone
title Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone
title_full Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone
title_fullStr Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone
title_full_unstemmed Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone
title_short Unravelling the Keto–Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone
title_sort unravelling the keto–enol tautomer dependent photochemistry and degradation pathways of the protonated uva filter avobenzone
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7168606/
https://www.ncbi.nlm.nih.gov/pubmed/32208697
http://dx.doi.org/10.1021/acs.jpca.0c01295
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