Insights into the photoprotection mechanism of the UV filter homosalate

Holt, Emily L.; Krokidi, Konstantina M.; Turner, Matthew A. P.; Mishra, Piyush; Zwier, Timothy S.; Rodrigues, Natércia d. N.; Stavros, Vasilios G.

doi:10.1039/d0cp02610g

Cited by 29 publications

(50 citation statements)

References 77 publications

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“…42,43 For example, ESHT dynamics in other common sunscreen molecules like homosalate, oxybenzone and methyl salicylate are reported to occur within 200 fs. 16,44,45 ESHT in DHHB on such timescales is not directly observed in our measurements, but is compatible with quenching of most of the SE from DHHB (S1 enol) in CYCH within our ~150 fs TEAS instrument response. The 𝜏Enol = 7 -20 ps time constants for decay of S1-enol ESA, with values depending on the solvent, are attributed to electronic relaxation of the excited DHHB from its S1-enol to the S0 electronic ground state.…”

Section: Iiiiiii Spectralsupporting

confidence: 82%

Influence of the Solvent Environment on the Ultrafast Relaxation Pathways of a Sunscreen Molecule Diethylamino Hydroxybenzoyl Hexyl Benzoate

et al. 2021

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The excited-state dynamics of photoexcited diethylamino hydroxybenzoyl hexyl benzoate (DHHB), a UVA absorber widely used in sunscreen formulations, are studied with transient electronic and vibrational absorption spectroscopy methods in four different solvents. In the polar solvents methanol, dimethyl sulfoxide (DMSO) and acetonitrile, strong stimulated emission (SE) is observed at early time delays after photoexcitation at a near-UV wavelength of ex = 360 nm, and decays with time constants of 420 fs in methanol and 770 fs in DMSO. The majority (~95%) of photoexcited DHHB returns to the ground state with time constants of 15 ps in methanol and 25 ps in DMSO. In the non-polar solvent cyclohexane, ~98%of DHHB photoexcited at ex = 345 nm relaxes to the ground state with a ~10 ps time constant, and the SE is weak. DHHB preferentially adopts an enol form in its ground S0 state, but excited state absorption (ESA) bands seen in TEAS are assigned to both the S1-keto and S1-enol forms, indicating a role for ultrafast intramolecular excited state hydrogen transfer (ESHT). This ESHT is inhibited by polar solvents. The two S1 tautomers decay with similar time scales to the observed recovery of ground state population. For molecules that avoid ESHT, torsion around a central C-C bond minimizes the S1-enol energy, quenches the SE, and is proposed to lead to a conical intersection with the S0 state that mediates the ground state recovery.A competing trans-enol isomeric photoproduct is observed as a minor competitor to parent recovery in polar solvents. Evidence is presented for triplet (T1) enol production in polar solvents, and for T1 quenching by octocrylene, a common UVB absorber sunscreen additive. The T1 keto form is observed in cyclohexane solution.

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Section: Iiiiiii Spectralsupporting

confidence: 82%

Influence of the Solvent Environment on the Ultrafast Relaxation Pathways of a Sunscreen Molecule Diethylamino Hydroxybenzoyl Hexyl Benzoate

et al. 2021

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“…Time-dependent DFT calculations were conducted upon this structure at the PBE0/ aug-pVTZ level of theory to calculate vertical excitation energies for both singlet and triplet excited states and are presented in section S3 of SM. This level of theory has been used successfully in the literature in previous studies on other organic chromophores [51][52][53]. Figure 2 (top) presents TR-Iϒ and TR-PES transients of trans-MC respectively along with the extracted timeconstants.…”

Section: Methodsmentioning

confidence: 99%

A systematic approach to methyl cinnamate photodynamics

et al. 2020

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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* (1 1 ππ*) state, there is initial decay to the lowest lying singlet 1 nπ* (1 1 nπ*) 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 1 1 ππ* 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 1 H NMR studies, these studies demonstrate that trans-cis isomerisation is preserved in the more complex, cyclohexane solution environment.

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“…[20][21][22] Transient electronic absorption spectroscopy (herein abbreviated as TEAS), is an ultrafast pump-probe technique that has been utilised previously to explore the photoprotection mechanisms of many individual UV filters in solution, including avobenzone; additional examples include benzophenone-3, ethylhexyl methoxycinnamate, homosalate, ethylhexyl salicylate, octocrylene and diethylamino hydroxybenzoyl hexyl benzoate. [23][24][25][26][27][28] An ideal sunscreen filter should be able to dissipate excited state energy safely (ideally non-radiatively) and rapidly (within femtoseconds, 1 fs = 10 À15 s, to picoseconds, 1 ps = 10 À12 s). This reduces the likelihood of harmful side reactions such as forming triplet states, or fragmentation of the molecule.…”

Section: Introductionmentioning

confidence: 99%

Determining the photostability of avobenzone in sunscreen formulation models using ultrafast spectroscopy

Holt

Rodrigues

Cebrián³

et al. 2021

Phys. Chem. Chem. Phys.

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Insights into the photoprotection mechanism of the UV filter homosalate

Abstract: Homosalate has been found to exhibit favourable photophysics for inclusion in sunscreens, using a combination of spectroscopic and computational approaches.

Cited by 29 publications

References 77 publications

Influence of the Solvent Environment on the Ultrafast Relaxation Pathways of a Sunscreen Molecule Diethylamino Hydroxybenzoyl Hexyl Benzoate

Influence of the Solvent Environment on the Ultrafast Relaxation Pathways of a Sunscreen Molecule Diethylamino Hydroxybenzoyl Hexyl Benzoate

A systematic approach to methyl cinnamate photodynamics

Determining the photostability of avobenzone in sunscreen formulation models using ultrafast spectroscopy

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