Insights into the photoprotection mechanism of the UV filter homosalate. Issue 27 (30th June 2020)

• Record Type: Journal Article
• Authors: Holt, Emily L.; Krokidi, Konstantina M.; Turner, Matthew A. P.; Mishra, Piyush; Zwier, Timothy S.; Rodrigues, Natércia d. N.; Stavros, Vasilios G.
• Is Part Of: Physical chemistry chemical physics. Volume 22:Issue 27(2020)
• Page Start: 15509
• Page End: 15519
• Publication Date: 2020-06-30
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d0cp02610g
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Homosalate has been found to exhibit favourable photophysics for inclusion in sunscreens, using a combination of spectroscopic and computational approaches. Abstract : Homosalate (HMS) is a salicylate molecule that is commonly included within commercial sunscreen formulations to provide protection from the adverse effects of ultraviolet (UV) radiation exposure. In the present work, the mechanisms by which HMS provides UV photoprotection are unravelled, using a multi-pronged approach involving a combination of time-resolved ultrafast laser spectroscopy in the gas-phase and in solution, laser-induced fluorescence, steady-state absorption spectroscopy, and computational methods. The unique combination of these techniques allow us to show that the enol tautomer of HMS undergoes ultrafast excited state intramolecular proton transfer (ESIPT) upon photoexcitation in the UVB (290–320 nm) region; once in the keto tautomer, the excess energy is predominantly dissipated non-radiatively. Sharp transitions are observed in the LIF spectrum at close-to-origin excitation energies, which points towards the potential presence of a second conformer that does not undergo ESIPT. These studies demonstrate that, overall, HMS exhibits mostly favourable photophysical characteristics of a UV filter for inclusion in sunscreen formulations.