title: Bottom-up excited state dynamics of two cinnamate-based sunscreen filter molecules.
abstract: Methyl-E-4-methoxycinnamate (E-MMC) is a model chromophore of the commonly used commercial sunscreen agent, 2-ethylhexyl-E-4-methoxycinnamate (E-EHMC). In an effort to garner a molecular-level understanding of the photoprotection mechanisms in operation with E-EHMC, we have used time-resolved pump-probe spectroscopy to explore E-MMC's and E-EHMC's excited state dynamics upon UV-B photoexcitation to the S1(11ππ*) state in both the gas- and solution-phase. In the gas-phase, our studies suggest that the excited state dynamics are driven by non-radiative decay from the 11ππ* to the S3(11nπ*) state, followed by de-excitation from the 11nπ* to the ground electronic state (S0). Using both a non-polar-aprotic solvent, cyclohexane, and a polar-protic solvent, methanol, we investigated E-MMC and E-EHMC's photochemistry in a more realistic, 'closer-to-shelf' environment. A stark change to the excited state dynamics in the gas-phase is observed in the solution-phase suggesting that the dynamics are now driven by efficient E/Z isomerisation from the initially photoexcited 11ππ* state to S0.
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk and ENS de Cachan, 61 Avenue du Président Wilson, 94230, Cachan, France.
authors.forename: Yoann
authors.initials: Y
authors.lastname: Peperstraete
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: Staniforth
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors.forename: Lewis A
authors.initials: LA
authors.lastname: Baker
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors.forename: Natércia D N
authors.initials: ND
authors.lastname: Rodrigues
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors.forename: Neil C
authors.initials: NC
authors.lastname: Cole-Filipiak
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors.forename: Wen-Dong
authors.initials: WD
authors.lastname: Quan
authors.affiliation: University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors.forename: Vasilios G
authors.initials: VG
authors.lastname: Stavros