A systematic approach to methyl cinnamate photodynamics

ABSTRACT

Methyl cinnamate (MC) is an ester within the cinnamate family. Recent time-resolved gas-phase studies have suggested that upon excitation to its first singlet ππ* (1¹ππ*) state, there is initial decay to the lowest lying singlet ¹nπ* (1¹nπ*) state within 10 ps, en route to trans–cis isomerisation. In the present study, we have implemented time-resolved ion yield (TR-IY) and time-resolved photoelectron spectroscopy (TR-PES) experiments in the gas-phase to precisely determine the lifetime of the 1¹ππ* state. We found this lifetime to be ∼ 4.5 ps using both TR-IY and TR-PES. MC was also studied in a more complex cyclohexane solution environment, using transient electronic absorption spectroscopy. Along with complementary steady-state irradiation and ¹H NMR studies, these studies demonstrate that trans–cis isomerisation is preserved in the more complex, cyclohexane solution environment.

GRAPHICAL ABSTRACT

KEYWORDS:

• Sunscreen
• photochemistry
• ultrafast laser spectroscopy
• photoisomerisation
• triplet state

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Acknowledgements

The authors would like to thank the Warwick Centre for Ultrafast Spectroscopy (WCUS) for the use of the Cary 60 and Fluorolog-3. Computing facilities were provided by the Scientific Computing Research Technology Platform of the University of Warwick. We acknowledge the use of Athena at HPC Midlands+, which was funded by the Engineering and Physical Sciences Research Council (EPSRC) by Grant EP/P020232/1, in this research, as part of the HPC Midlands+ consortium. K.M.K. thanks the EPSRC for doctoral funding. M.A.P.T. thanks the EPSRC for a PhD studentship through the EPSRC Centre for Doctoral Training in Molecular Analytical Science, grant number EP/L015307/1. Finally, V.G.S. thanks the HO2020 FET-OPEN Grant BoostCrop for financial support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

We acknowledge the use of Athena at HPC Midlands+, which was funded by the Engineering and Physical Sciences Research Council (EPSRC) by Grant EP/P020232/1, in this research, as part of the HPC Midlands+ consortium. K.M.K. thanks the EPSRC for doctoral funding. M.A.P.T. thanks the EPSRC for a PhD studentship through the EPSRC Centre for Doctoral Training in Molecular Analytical Science, grant number EP/L015307/1. Finally, V.G.S. thanks the European Union's Horizon 2020 Research and Innovation Programme, under the grant agreement number 828753.