Octocrylene (OCR) is a widely used organic sunscreen molecules, and is a dominant component of many sunscreen formulations. Here, we perform the first measurements on the protonated form of OCR, i. e. [OCR+H]+, to probe whether protonation affects the molecule's photostability. The novel photochemical technique of UV laser-interfaced mass spectrometry is employed from 400–216 nm, revealing that the electronic absorption spectrum of OCR across the S1 and S2 states red shift by 40 nm upon protonation. Our measurements reveal that [OCR+H]+ predominantly undergoes photofragmentation into the m/z 250 and 232 ionic products, associated with loss of its bulky alkyl side chain, and subsequent loss of water, respectively. We compare the photochemical fragmentation results with higher-energy collisional dissociation results to investigate the nature of the photodynamics that occur following UV absorption. The excited state decay pathways over the S1 and S2 excited states of [OCR+H]+ are associated with statistical fragmentation in line with dominant ultrafast decay. This behaviour mirrors that of neutral OCR, demonstrating that protonation does not affect the ultrafast decay pathways of this sunscreen molecule. We discuss our results in the context of the known breakdown of OCR into benzophenone, identifying a potential photoactivated pathway to benzophenone formation in solution.
Bibliographical noteFunding Information:
This work was funded through the Leverhulme Trust Research Project Grant RPG‐2017‐147. We thank the University of York and the Department of Chemistry for provision of funds for the OPO laser system. The York Centre of Excellence in Mass Spectrometry, used for the CID work, was created thanks to a major capital investment through Science City York, supported by Yorkshire Forward with funds from the Northern Way Initiative, and has more recently received additional support from the EPSRC and BBSRC. We also thank Mathew Hawkridge and Edward Matthews for their early contributions to this work.
© 2023 The Authors. ChemPhotoChem published by Wiley-VCH GmbH.
- mass spectrometry