Photophysics of a UV‐B Filter 4‐Methylbenzylidene Camphor: Intersystem Crossing Plays an Important Role

Fang, Ye‐Guang; Li, Chunxiang; Chang, Xue-Ping; Cui, Ganglong

doi:10.1002/cphc.201701230

Cited by 15 publications

(15 citation statements)

References 67 publications

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“…The 6-31G* basis set was used due to the large computational efforts in MS-CASPT2 calculations and non-adiabatic dynamics simulations considering our limited computational sources. However, this basis set is robust for small organic molecules and could provide at least qualitatively correct results for these systems as shown in our previous works [ 106 , 107 , 108 ]. As the first theoretical work investigating the photoinduced processes of nucleoside-based diarylethene, we performed all our calculations in vacuum without considering any environmental effects.…”

Section: Methodssupporting

confidence: 55%

“On-The-Fly” Non-Adiabatic Dynamics Simulations on Photoinduced Ring-Closing Reaction of a Nucleoside-Based Diarylethene Photoswitch

et al. 2021

Molecules

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Nucleoside-based diarylethenes are emerging as an especial class of photochromic compounds that have potential applications in regulating biological systems using noninvasive light with high spatio-temporal resolution. However, relevant microscopic photochromic mechanisms at atomic level of these novel diarylethenes remain to be explored. Herein, we have employed static electronic structure calculations (MS-CASPT2//M06-2X, MS-CASPT2//SA-CASSCF) in combination with non-adiabatic dynamics simulations to explore the related photoinduced ring-closing reaction of a typical nucleoside-based diarylethene photoswitch, namely, PS-IV. Upon excitation with UV light, the open form PS-IV can be excited to a spectroscopically bright S1 state. After that, the molecule relaxes to the conical intersection region within 150 fs according to the barrierless relaxed scan of the C1–C6 bond, which is followed by an immediate deactivation to the ground state. The conical intersection structure is very similar to the ground state transition state structure which connects the open and closed forms of PS-IV, and therefore plays a crucial role in the photochromism of PS-IV. Besides, after analyzing the hopping structures, we conclude that the ring closing reaction cannot complete in the S1 state alone since all the C1–C6 distances of the hopping structures are larger than 2.00 Å. Once hopping to the ground state, the molecules either return to the original open form of PS-IV or produce the closed form of PS-IV within 100 fs, and the ring closing quantum yield is estimated to be 56%. Our present work not only elucidates the ultrafast photoinduced pericyclic reaction of the nucleoside-based diarylethene PS-IV, but can also be helpful for the future design of novel nucleoside-based diarylethenes with better performance.

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Section: Methodssupporting

confidence: 55%

“On-The-Fly” Non-Adiabatic Dynamics Simulations on Photoinduced Ring-Closing Reaction of a Nucleoside-Based Diarylethene Photoswitch

et al. 2021

Molecules

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“…The chemical filters used in modern commercial sunscreens play a critical role in photoprotection, which can dissipate the absorbed excessive UV radiation energy as heat through some nondestructive pathways to provide an additionally effective photoprotection for the skin. 2−4 Thus, in recent years, a large number of experimental and theoretical studies have focused on the excited-state relaxation dynamics of a variety of chemical UV filters including cinnamates, 5−22 eumelanins, 23−27 benzophenones, 28−37 camphor, 38,39 octocrylenes, 40−42 and salicylates. 43−46 Methyl salicylate (MS) as a subunit of larger salicylates found in commercial sunscreens has become an ideal model for a bottom-up approach to understand the photodynamics of the more complex salicylates such as octyl salicylate and homomethyl salicylate (HMS).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Ultraviolet (UV) radiation has a comprehensive impact on human health, such as appropriate exposure to UV can generate vitamin D that has a beneficial effect on human health, but excessive UV exposure can cause detrimental effects such as sunburn, photocarcinogenesis, and photoaging. − Sunscreens are believed to be an effective tool in providing photoprotection for our skin against the UV radiation. The chemical filters used in modern commercial sunscreens play a critical role in photoprotection, which can dissipate the absorbed excessive UV radiation energy as heat through some nondestructive pathways to provide an additionally effective photoprotection for the skin. − Thus, in recent years, a large number of experimental and theoretical studies have focused on the excited-state relaxation dynamics of a variety of chemical UV filters including cinnamates, − eumelanins, − benzophenones, − camphor, , octocrylenes, − and salicylates. − …”

Section: Introductionmentioning

confidence: 99%

Quantum Mechanics/Molecular Mechanics Studies on the Photophysical Mechanism of Methyl Salicylate

et al. 2021

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Methyl salicylate (MS) as a subunit of larger salicylates found in commercial sunscreens has been shown to exhibit keto–enol tautomerization and dual fluorescence emission via excited-state intramolecular proton transfer (ESIPT) after the absorption of ultraviolet (UV) radiation. However, its excited-state relaxation mechanism is unclear. Herein, we have employed the quantum mechanics(CASPT2//CASSCF)/molecular mechanics method to explore the ESIPT and excited-state relaxation mechanism of MS in the lowest three electronic states, that is, S0, S1, and T1 states, in a methanol solution. Based on the optimized geometric and electronic structures, conical intersections and crossing points, and minimum-energy paths combined with the computed linearly interpolated Cartesian coordinate paths, the photophysical mechanism of MS has been proposed. The S1 state is a spectroscopically bright 1ππ* state in the Franck–Condon region. From the initially populated S1 state, there exist three nonradiative relaxation paths to repopulate the S0 state. In the first one, the S1 system (i.e., ketoB form) first undergoes an ESIPT path to generate an S1 tautomer (i.e., enol form) that exhibits a large Stokes shift in experiments. The generated S1 enol tautomer further evolves toward the nearby S1/S0 conical intersection and then hops to the S0 state, followed by the backward ground-state intramolecular proton transfer (GSIPT) to the initial ketoB form S0 state. In the second one, the S1 system first hops through the S1 → T1 intersystem crossing (ISC) to the T1 state, which then further decays to the S0 state via T1 → S0 ISC at the T1/S0 crossing point. In the third path, the T1 system that stems from the S1 → T1 ISC process via the S1/T1 crossing point first takes place a T1 ESIPT to generate a T1 enol tautomer, which can further decay to the S0 state via T1-to-S0 ISC. Finally, the GSIPT occurs to back the system to the initial ketoB form S0 state. Our present work could contribute to understanding the photophysics of MS and its derivatives.

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“…Despite the importance of sunscreens to human health remarkably little was known until very recently about how photoactive organic sunscreens function in terms of their detailed molecular potential energy surfaces ( Karsili et al, 2014 ; Baker et al, 2017 ). An organic sunscreen molecule works by absorbing damaging UV radiation, and dispersing it into less harmful forms of energy ( Forestier, 2008 ; Karsili et al, 2014 ; Baker et al, 2017 ; Losantos et al, 2018 ). One key requisite for such molecules to act as chemical sunscreens is that they should not undergo chemical change or induce unwanted toxicity upon exposure to UV light ( Forestier, 2008 ).…”

Section: Introductionmentioning

confidence: 99%

Illuminating the Effect of the Local Environment on the Performance of Organic Sunscreens: Insights From Laser Spectroscopy of Isolated Molecules and Complexes

Wong

Dessent

2022

Front. Chem.

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Sunscreens are essential for protecting the skin from UV radiation, but significant questions remain about the fundamental molecular-level processes by which they operate. In this mini review, we provide an overview of recent advanced laser spectroscopic studies that have probed how the local, chemical environment of an organic sunscreen affects its performance. We highlight experiments where UV laser spectroscopy has been performed on isolated gas-phase sunscreen molecules and complexes. These experiments reveal how pH, alkali metal cation binding, and solvation perturb the geometric and hence electronic structures of sunscreen molecules, and hence their non-radiative decay pathways. A better understanding of how these interactions impact on the performance of individual sunscreens will inform the rational design of future sunscreens and their optimum formulations.

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Photophysics of a UV‐B Filter 4‐Methylbenzylidene Camphor: Intersystem Crossing Plays an Important Role

Cited by 15 publications

References 67 publications

“On-The-Fly” Non-Adiabatic Dynamics Simulations on Photoinduced Ring-Closing Reaction of a Nucleoside-Based Diarylethene Photoswitch

“On-The-Fly” Non-Adiabatic Dynamics Simulations on Photoinduced Ring-Closing Reaction of a Nucleoside-Based Diarylethene Photoswitch

Quantum Mechanics/Molecular Mechanics Studies on the Photophysical Mechanism of Methyl Salicylate

Illuminating the Effect of the Local Environment on the Performance of Organic Sunscreens: Insights From Laser Spectroscopy of Isolated Molecules and Complexes

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