Photoexcited States of <scp>UV</scp> Absorbers, Benzophenone Derivatives

Kumasaka, Ryo; Kikuchi, Azusa; Yagi, Mikio

doi:10.1111/php.12257

Cited by 31 publications

(33 citation statements)

References 39 publications

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“…Given previous condensed phase observations, triplet state formation is one possible assignment, 12 although recent ab initio electronic structure calculations of likely triplet photoproducts coupled with transient vibrational absorption studies suggest such triplet states are negligible. Given previous condensed phase observations, triplet state formation is one possible assignment, 12 although recent ab initio electronic structure calculations of likely triplet photoproducts coupled with transient vibrational absorption studies suggest such triplet states are negligible.…”

Section: Cyclohexanementioning

confidence: 99%

Broadband ultrafast photoprotection by oxybenzone across the UVB and UVC spectral regions

Baker

Horbury

Greenough

et al. 2015

Photochem Photobiol Sci

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Recent studies have shed light on the energy dissipation mechanism of oxybenzone, a common ingredient in commercial sunscreens. After UVA photoexcitation, the dissipation mechanism may be understood in terms of an initial ultrafast excited state enol → keto tautomerisation, followed by nonadiabatic transfer to the ground electronic state and subsequent collisional relaxation to the starting enol tautomer. We expand on these studies using femtosecond transient electronic absorption spectroscopy to understand the non-radiative relaxation pathways of oxybenzone in cyclohexane and in methanol after UVB and UVC excitation. We find that the relaxation pathway may be understood in the same way as when exciting in the UVA region, concluding that oxybenzone displays proficient broadband non-radiative photoprotection, and thus photophysically justifying its inclusion in sunscreen mixtures.

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Section: Cyclohexanementioning

confidence: 99%

Broadband ultrafast photoprotection by oxybenzone across the UVB and UVC spectral regions

Baker

Horbury

Greenough

et al. 2015

Photochem Photobiol Sci

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“…Given previous condensed phase observations, 9 triplet state formation must be one possible assignment for the emerging positive feature in the TVA spectra, but comparison with calculated triplet state spectra for several different OB structures/isomers tends to rule out this suggestion (see SI, Figure S8). Based on the recent ab initio electronic structure calculations 10 and findings from experimental studies of twisted ESHT mechanisms in related systems, 27-29 we propose an alternative assignment for the signal carrier of this new feature at ~1640 cm -1 .…”

mentioning

confidence: 99%

“…10 These studies identified internal conversion (IC) via an electron-driven excited state hydrogen atom transfer (ESHT) mechanism as a plausible energy relaxation pathway, in concordance with studies in similar species containing hydrogen donor (OH)-acceptor (CO) sites in close proximity. 16,17 Recent studies have also revealed some probability of excited state OB molecules undergoing intersystem crossing (ISC) to long lived triplet states 9 and homolytic O-H bond fission to yield phenoxyl radicals. 18 The current evidence thus suggests that OB is photostable under UV irradiation (notwithstanding the undesirable minor ISC and O-H bond fission channels), but this cannot be confirmed whilst the OB excited state decay mechanism remains in question.…”

mentioning

confidence: 99%

Probing the Ultrafast Energy Dissipation Mechanism of the Sunscreen Oxybenzone after UVA Irradiation

Baker¹,

Horbury²,

Greenough³

et al. 2015

J. Phys. Chem. Lett.

106

141

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(2015) Probing the ultrafast energy dissipation mechanism of the sunscreen oxybenzone after UVA irradiation. Journal of Physical Chemistry Letters, 6 (8). pp. 1363-1368. Permanent WRAP URL:http://wrap.warwick.ac.uk/83198 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry Letters, copyright © American Chemical Society after peer review and technical editing by the publisher.To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpclett.5b00417 A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. ABSTRACT: Oxybenzone is a common constituent of many commercially available sunscreens providing photoprotection from ultraviolet light incident on the skin. Femtosecond transient electronic and vibrational absorption spectroscopies have been used to investigate the non-radiative relaxation pathways of oxybenzone in cyclohexane and methanol after excitation in the UVA region. The present data suggest that the photoprotective properties of oxybenzone can be understood in terms of an initial ultrafast excited state enol  keto tautomerization, followed by efficient internal conversion and subsequent vibrational relaxation to the ground state (enol) tautomer.TOC GRAPHIC

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“…The ESIPT fluorophores, including HBO and its analogs, carry large Stokes shifts (up to ~10 000 cm −1 ) and a mechanism to dissipate excess excitation energy via rapid excited state proton transfer (Scheme ) . Based on these properties, ESIPT dyes are promising components in new dye laser technologies , and as active ingredients in sunscreens and photostabilizers for protection from UV damage . From a fundamental perspective, ESIPT is only one of several photophysical pathways that these molecules could undergo.…”

Section: Introductionmentioning

confidence: 99%

“…These representations are qualitatively helpful in understanding the acidity and molecular dipole changes upon photoexcitation. promising components in new dye laser technologies (15,16), and as active ingredients in sunscreens (17)(18)(19) and photostabilizers for protection from UV damage (20)(21)(22). From a fundamental perspective, ESIPT is only one of several photophysical pathways that these molecules could undergo.…”

Section: Introductionmentioning

confidence: 99%

Absorption and Emission Sensitivity of 2‐(2′‐Hydroxyphenyl)benzoxazole to Solvents and Impurities

Zhao

Tang

Sreenath

et al. 2014

Photochem & Photobiology

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2-(2'-Hydroxyphenyl)benzoxazole (HBO) is known for undergoing intramolecular proton transfer in the excited state to result in the emission of its tautomer. A minor long-wavelength absorption band in the range 370-420 nm has been reported in highly polar solvents such as dimethylsulfoxide (DMSO). However, the nature of this species has not been entirely clarified. In this work, we provide evidence that this long-wavelength absorption band might have been caused by base or metal salt impurities that are introduced into the spectral sample during solvent transport using glass Pasteur pipettes. The contamination by base or metal salt could be avoided by using borosilicate glass syringes or nonglass pipettes in sample handling. Quantum chemical calculations conclude that solvent-mediated deprotonation is too energetically costly to occur without the aid of a base of an adequate strength. In the presence of such a base, the deprotonation of HBO and its effect on emission are investigated in dichloromethane and DMSO, the latter of which facilitates deprotonation much more readily than the former. Finally, the absorption and emission spectra of HBO in 13 solvents are reported, from which it is concluded that ESIPT is hindered in polar solvents that are also strong hydrogen bond acceptors.

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Photoexcited States of UV Absorbers, Benzophenone Derivatives

Cited by 31 publications

References 39 publications

Broadband ultrafast photoprotection by oxybenzone across the UVB and UVC spectral regions

Broadband ultrafast photoprotection by oxybenzone across the UVB and UVC spectral regions

Probing the Ultrafast Energy Dissipation Mechanism of the Sunscreen Oxybenzone after UVA Irradiation

Absorption and Emission Sensitivity of 2‐(2′‐Hydroxyphenyl)benzoxazole to Solvents and Impurities

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