1
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Fan J, Lemmens AK, Sanders H, Hilbers M, Roeterdink W, Jan Buma W. Urocanic acid as a novel scaffold for next-gen nature-inspired sunscreens: I. electronic laser spectroscopy under isolated conditions. Phys Chem Chem Phys 2024. [PMID: 39007338 DOI: 10.1039/d4cp02087a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Urocanic acid is a naturally occurring UV-A and UV-B absorbing compound found in the skin. Its use in artificial sunscreens has been abandoned because of health risks associated with the cis isomer. Here we report laser spectroscopic studies on urocanic acid and various substituted derivatives under supersonically cooled conditions. We find that the spectroscopy and excited-state dynamics of urocanic acid are dominantly determined by the nearly degenerate 1nπ* and 1ππ* electronically excited states. These properties are only affected to a minor extent by esterification of the carboxylic acid group or NH alkylation of the N3H tautomer. Tautomerization, on the other hand, has a much more profound influence and leads-from a photoprotective point of view-to more favorable excited-state dynamics. The approach presented here paves the way to tailoring the photoactive properties of urocanic acid for specific applications amongst which their use as safe UV filters.
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Affiliation(s)
- Jiayun Fan
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
| | - Alexander K Lemmens
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
- Institute for Molecules and Materials, Radboud University, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Hans Sanders
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
| | - Michiel Hilbers
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
| | - Wim Roeterdink
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
| | - Wybren Jan Buma
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
- Institute for Molecules and Materials, Radboud University, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
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2
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Vink MA, Alarcan J, Martens J, Buma WJ, Braeuning A, Berden G, Oomens J. Structural Elucidation of Agrochemical Metabolic Transformation Products Based on Infrared Ion Spectroscopy to Improve In Silico Toxicity Assessment. Chem Res Toxicol 2024; 37:81-97. [PMID: 38118149 PMCID: PMC10792670 DOI: 10.1021/acs.chemrestox.3c00316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 12/03/2023] [Accepted: 12/05/2023] [Indexed: 12/22/2023]
Abstract
Toxicological assessments of newly developed agrochemical agents consider chemical modifications and their metabolic and biotransformation products. To carry out an in silico hazard assessment, understanding the type of chemical modification and its location on the original compound can greatly enhance the reliability of the evaluation. Here, we present and apply a method based on liquid chromatography-mass spectrometry (LC-MS) enhanced with infrared ion spectroscopy (IRIS) to better delineate the molecular structures of transformation products before in silico toxicology evaluation. IRIS facilitates the recording of IR spectra directly in the mass spectrometer for features selected by retention time and mass-to-charge ratio. By utilizing quantum-chemically predicted IR spectra for candidate molecular structures, one can either derive the actual structure or significantly reduce the number of (isomeric) candidate structures. This approach can assist in making informed decisions. We apply this method to a plant growth stimulant, digeraniol sinapoyl malate (DGSM), that is currently under development. Incubation of the compound in Caco-2 and HepaRG cell lines in multiwell plates and analysis by LC-MS reveals oxidation, glucuronidation, and sulfonation metabolic products, whose structures were elucidated by IRIS and used as input for an in silico toxicology assessment. The toxicity of isomeric metabolites predicted by in silico tools was also assessed, which revealed that assigning the right metabolite structure is an important step in the overall toxicity assessment of the agrochemical. We believe this identification approach can be advantageous when specific isomers are significantly more hazardous than others and can help better understand metabolic pathways.
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Affiliation(s)
- Matthias
J. A. Vink
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Jimmy Alarcan
- Department
of Food Safety, German Federal Institute
for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Jonathan Martens
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Wybren Jan Buma
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
- van’t
Hoff Institute for Molecular Sciences, University
of Amsterdam, Science
Park 904, 1098 XH Amsterdam, The Netherlands
| | - Albert Braeuning
- Department
of Food Safety, German Federal Institute
for Risk Assessment, Max-Dohrn-Str. 8-10, 10589 Berlin, Germany
| | - Giel Berden
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Jos Oomens
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
- van’t
Hoff Institute for Molecular Sciences, University
of Amsterdam, Science
Park 904, 1098 XH Amsterdam, The Netherlands
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3
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Fan J, Buma WJ. Molecular beam laser spectroscopic studies of the photoactive properties of resveratrol. Photochem Photobiol Sci 2023:10.1007/s43630-023-00481-7. [PMID: 37921957 DOI: 10.1007/s43630-023-00481-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 09/04/2023] [Indexed: 11/05/2023]
Abstract
Resonance Enhanced MultiPhoton Ionization spectroscopic techniques coupled with laser desorption and supersonic cooling have been employed to elucidate the photoactive properties of resveratrol. The observed excitation spectra give evidence for an internal-energy dependent trans-cis isomerisation pathway in the electronically excited state, while pump-probe studies show dynamics that are in line with what is known for the parent compound, trans-stilbene. Similar studies have been performed on a derivative of resveratrol with methoxy instead of hydroxy groups, a compound aimed to reduce previously observed photodegradation pathways of resveratrol. Time-resolved studies of the latter compound under solution conditions have given further insight into its excited-state dynamics and support the isolated-molecule conclusions on the topology of the potential energy surface of the electronically excited state. Spectroscopic studies under prolonged irradiation conditions show that both compounds suffer from photodegradation, although in the alkylated compound other pathways appear to be involved than in resveratrol.
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Affiliation(s)
- Jiayun Fan
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Wybren Jan Buma
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
- Institute for Molecules and Materials, Radboud University, FELIX Laboratory, Toernooiveld 7c, 6525 ED, Nijmegen, The Netherlands.
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4
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Dalton J, Toldo JM, Allais F, Barbatti M, Stavros VG. Understanding the Impact of Symmetrical Substitution on the Photodynamics of Sinapate Esters Using Gas-Phase Ultrafast Spectroscopy. J Phys Chem Lett 2023; 14:8771-8779. [PMID: 37738948 PMCID: PMC10561265 DOI: 10.1021/acs.jpclett.3c02134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/08/2023] [Indexed: 09/24/2023]
Abstract
Two model biomimetic systems, ethyl sinapate (ES) and its symmetrical analogue, diethyl 2-(4-hydroxy-3,5-dimethoxybenzylidene)malonate (or diethyl sinapate, DES), are stripped to their core fundamentals through gas-phase spectroscopy to understand the underlying photophysics of photothermal materials. Following photoexcitation to the optically bright S1(ππ*) state, DES is found to repopulate the electronic ground state over 3 orders of magnitude quicker than its nonsymmetrical counterpart, ES. Our XMS-CASPT2 calculations shed light on the experimental results, revealing crucial differences in the potential energy surfaces and conical intersection topography between ES and DES. From this work, a peaked conical intersection, seen for DES, shows vital importance for the nonradiative ground-state recovery of photothermal materials. This fundamental comparative study highlights the potential impact that symmetrical substitution can have on the photodynamics of sinapate esters, providing a blueprint for future advancement in photothermal technology.
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Affiliation(s)
- Jack Dalton
- Department
of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, U.K.
| | | | - Florent Allais
- URD
Agro-Biotechnologies Industrielles, CEBB, AgroParisTech, 51110 Pomacle, France
| | - Mario Barbatti
- Aix Marseille Université,
CNRS, ICR, Marseille, France
- Institut
Universitaire de France, 75231 Paris, France
| | - Vasilios G. Stavros
- Department
of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, U.K.
- School
of Chemistry, University of Birmingham, Birmingham B15 2TT, U.K.
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5
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Vink MA, Schermer JJ, Martens J, Buma WJ, Berden G, Oomens J. Characterization of Solar Radiation-Induced Degradation Products of the Plant Sunscreen Sinapoyl Malate. ACS AGRICULTURAL SCIENCE & TECHNOLOGY 2023; 3:171-180. [PMID: 36846518 PMCID: PMC9945346 DOI: 10.1021/acsagscitech.2c00279] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 01/20/2023]
Abstract
Agricultural activities at lower temperatures lead to lower yields due to reduced plant growth. Applying photomolecular heater agrochemicals could boost yields under these conditions, but UV-induced degradation of these compounds needs to be assessed. In this study, we employ liquid chromatography-mass spectrometry (LC-MS) coupled with infrared ion spectroscopy (IRIS) to detect and identify the degradation products generated upon simulated solar irradiation of sinapoyl malate, a proposed photomolecular heater/UV filter compound. All major irradiation-induced degradation products are identified in terms of their full molecular structure by comparing the IRIS spectra obtained after LC fractionation and mass isolation with reference IR spectra obtained from quantum-chemical calculations. In cases where physical standards are available, a direct experimental-to-experimental comparison is possible for definitive structure identification. We find that the major degradation products originate from trans-to-cis isomerization, ester cleavage, and esterification reactions of sinapoyl malate. Preliminary in silico toxicity investigations using the VEGAHUB platform suggest no significant concerns for these degradation products' human and environmental safety. The identification workflow presented here can analogously be applied to break down products from other agrochemical compounds. As the method records IR spectra with the sensitivity of LC-MS, application to agricultural samples, e.g., from field trials, is foreseen.
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Affiliation(s)
- Matthias
J. A. Vink
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - John J. Schermer
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Jonathan Martens
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
| | - Wybren Jan Buma
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands,van’t
Hoff Institute for Molecular Sciences, University
of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Giel Berden
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands,
| | - Jos Oomens
- Institute
for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands,
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6
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Fan J, Finazzi L, Jan Buma W. Elucidating the photoprotective properties of natural UV screening agents: ZEKE-PFI spectroscopy of methyl sinapate. Phys Chem Chem Phys 2022; 24:3984-3993. [PMID: 35099484 DOI: 10.1039/d1cp05958k] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
As a prominent derivative of a natural sunscreen, methyl sinapate is an ideal candidate to provide fundamental insight into strategies on how to come to a rational design of artificial sunscreen filters with improved photoprotective properties. Here, static and time-resolved Zero Kinetic Energy-Pulsed Field Ionization (ZEKE-PFI) photoelectron spectroscopy has been used to study the spectroscopy and decay pathways of its electronically excited states. We find that different conformers are subject to distinct structural changes upon electronic excitation, and trace the structural changes that occur upon excitation back to the character of the LUMO. Ionization efficiency spectra in combination with pump-probe ZEKE-PFI spectra are consistent with the conclusion that the long-lived electronically excited state observed in the decay of the lowest excited singlet state is the lowest excited triplet state. Concurrently with providing information on the electronically excited states, the studies allow for a detailed characterization of the spectroscopic properties of the ground state of the radical ion, which is important in the context of the use of cinnamates in nature as antioxidants. Our studies determine the adiabatic ionization energies of the syn/cis, anti/cis and anti/trans conformers as 60 291.1 ± 0.5, 60 366.9 ± 0.5 and 60 503.9 ± 1.0 cm-1, respectively, and provide accurate vibrational fequencies of low-frequency modes of the molecular ion in its electronic ground state. Finally, the studies emphasize the important role of vibrational and electronic autoionization processes that start to dominate the ionization dynamics in non-rigid molecules of the present size.
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Affiliation(s)
- Jiayun Fan
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
| | - Laura Finazzi
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
| | - Wybren Jan Buma
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands. .,Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
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7
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Wong NGK, Dessent CEH. Illuminating the Effect of the Local Environment on the Performance of Organic Sunscreens: Insights From Laser Spectroscopy of Isolated Molecules and Complexes. Front Chem 2022; 9:812098. [PMID: 35096773 PMCID: PMC8789676 DOI: 10.3389/fchem.2021.812098] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 12/20/2021] [Indexed: 12/11/2022] Open
Abstract
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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Affiliation(s)
- Natalie G K Wong
- Department of Chemistry, University of York, York, United Kingdom
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8
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Chang XP, Zhang TS, Cui G. Theoretical Studies on the Excited-State Decay Mechanism of Homomenthyl Salicylate in a Gas Phase and an Acetonitrile Solution. J Phys Chem A 2021; 126:16-28. [PMID: 34963284 DOI: 10.1021/acs.jpca.1c07108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Here, we employ the CASPT2//CASSCF and QM(CASPT2//CASSCF)/MM approaches to explore the photochemical mechanism of homomenthyl salicylate (HMS) in vacuum and an acetonitrile solution. The results show that in both cases, the excited-state relaxation mainly involves a spectroscopically "bright" S1(1ππ*) state and the lower-lying T1 and T2 states. In the major relaxation pathway, the photoexcited S1 keto system first undergoes an essentially barrierless excited-state intramolecular proton transfer (ESIPT) to generate the S1 enol minimum, near which a favorable S1/S0 conical intersection decays the system to the S0 state followed by a reverse ground-state intramolecular proton transfer (GSIPT) to repopulate the initial S0 keto species. In the minor one, an S1/T2/T1 three-state intersection in the keto region makes the T1 state populated via direct and T2-mediated intersystem crossing (ISC) processes. In the T1 state, an ESIPT occurs, which is followed by ISC near a T1/S0 crossing point in the enol region to the S0 state and finally back to the S0 keto species. In addition, a T1/S0 crossing point near the T1 keto minimum can also help the system decay to the S0 keto species. However, small spin-orbit couplings between T1 and S0 at these T1/S0 crossing points make ISC to the S0 state very slow and make the system trapped in the T1 state for a while. The present work rationalizes not only the ultrafast excited-state decay dynamics of HMS but also its low quantum yield of phosphorescence at 77 K.
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Affiliation(s)
- Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, P. R. China
| | - Teng-Shuo Zhang
- College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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9
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Xie BB, Tang XF, Liu XY, Chang XP, Cui G. Mechanistic photophysics and photochemistry of unnatural bases and sunscreen molecules: insights from electronic structure calculations. Phys Chem Chem Phys 2021; 23:27124-27149. [PMID: 34849517 DOI: 10.1039/d1cp03994f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photophysics and photochemistry are basic subjects in the study of light-matter interactions and are ubiquitous in diverse fields such as biology, energy, materials, and environment. A full understanding of mechanistic photophysics and photochemistry underpins many recent advances and applications. This contribution first provides a short discussion on the theoretical calculation methods we have used in relevant studies, then we introduce our latest progress on the mechanistic photophysics and photochemistry of two classes of molecular systems, namely unnatural bases and sunscreens. For unnatural bases, we disclose the intrinsic driving forces for the ultrafast population to reactive triplet states, impacts of the position and degree of chalcogen substitutions, and the effects of complex environments. For sunscreen molecules, we reveal the photoprotection mechanisms that dissipate excess photon energy to the surroundings by ultrafast internal conversion to the ground state. Finally, relevant theoretical challenges and outlooks are discussed.
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Affiliation(s)
- Bin-Bin Xie
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
| | - Xiu-Fang Tang
- Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
| | - Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, Sichuan, 610068, China
| | - Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
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10
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Toldo JM, do Casal MT, Barbatti M. Mechanistic Aspects of the Photophysics of UVA Filters Based on Meldrum Derivatives. J Phys Chem A 2021; 125:5499-5508. [PMID: 34151555 DOI: 10.1021/acs.jpca.1c03315] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Skin photoprotection against UVA radiation is crucial, but it is hindered by the sparsity of approved commercial UVA filters. Sinapoyl malate (SM) derivatives are promising candidates for a new class of UVA filters. They have been previously identified as an efficient photoprotective sunscreen in plants due to their fast nonradiative energy dissipation. Combining experimental and computational results, in our previous letter (J. Phys. Chem. Lett. 2021, 12, 337-344) we showed that coumaryl Meldrum (CMe) and sinapoyl Meldrum (SMe) are outstanding candidates for UVA filters in sunscreen formulations. Here, we deliver a comprehensive computational characterization of the excited-state dynamics of these molecules. Using reaction pathways and excited-state dynamics simulations, we could elucidate the photodeactivation mechanism of these molecules. Upon photoexcitation, they follow a two-step logistic decay. First, an ultrafast and efficient relaxation stabilizes the excited state alongside a 90° twisting around the allylic double bond, giving rise to a minimum with a twisted intramolecular excited-state (TICT) character. From this minimum, internal conversion to the ground state occurs after overcoming a 0.2 eV barrier. Minor differences in the nonradiative decay and fluorescence of CMe and SMe are associated with an additional minimum present only in the latter.
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Affiliation(s)
- Josene M Toldo
- Aix Marseille Université, CNRS, ICR, Av. Esc. Normandie-Niemen BJ5-D22, Marseille 13397, France
| | - Mariana T do Casal
- Aix Marseille Université, CNRS, ICR, Av. Esc. Normandie-Niemen BJ5-D22, Marseille 13397, France
| | - Mario Barbatti
- Aix Marseille Université, CNRS, ICR, Av. Esc. Normandie-Niemen BJ5-D22, Marseille 13397, France
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11
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Fois E, Oriani M, Tabacchi G. A post-HF approach to the sunscreen octyl methoxycinnamate. J Chem Phys 2021; 154:144304. [PMID: 33858162 DOI: 10.1063/5.0046118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Octyl methoxycinnamate (2-ethylhexyl 4-methoxycinnamate, OMC) is a commercial sunscreen known as octinoxate with excellent UVB filter properties. However, it is known to undergo a series of photodegradation processes that decrease its effectiveness as a UVB filter. In particular, the trans (E) form-which is considered so far as the most stable isomer-converts to the cis (Z) form under the effect of light. In this work, by using post-Hartree-Fock approaches [CCSD, CCSD(t), and CCSD + T(CCSD)] on ground state OMC geometries optimized at the MP2 level, we show that the cis and trans forms of the gas-phase OMC molecule have comparable stability. Test calculations on the same structures with a series of dispersion-corrected density functional theory-based approaches including the B2PLYP double hybrid predict the trans structures to be energetically favored, missing the subtle stabilization of cis-OMC. Our results suggest that the cis form is stabilized by intra-molecular dispersion interactions, leading to a folded more compact structure than the trans isomer.
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Affiliation(s)
- Ettore Fois
- Department of Science and High Technology, University of Insubria and INSTM UdR Insubria, Via Valleggio 11, I-22100 Como, Italy
| | - Mario Oriani
- Department of Science and High Technology, University of Insubria and INSTM UdR Insubria, Via Valleggio 11, I-22100 Como, Italy
| | - Gloria Tabacchi
- Department of Science and High Technology, University of Insubria and INSTM UdR Insubria, Via Valleggio 11, I-22100 Como, Italy
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12
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Chang XP, Zhang TS, Fang YG, Cui G. Quantum Mechanics/Molecular Mechanics Studies on the Photophysical Mechanism of Methyl Salicylate. J Phys Chem A 2021; 125:1880-1891. [PMID: 33645980 DOI: 10.1021/acs.jpca.0c10589] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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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Affiliation(s)
- Xue-Ping Chang
- College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, P. R. China
| | - Teng-Shuo Zhang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ye-Guang Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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13
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Kinoshita SN, Harabuchi Y, Inokuchi Y, Maeda S, Ehara M, Yamazaki K, Ebata T. Substitution effect on the nonradiative decay and trans → cis photoisomerization route: a guideline to develop efficient cinnamate-based sunscreens. Phys Chem Chem Phys 2021; 23:834-845. [PMID: 33284297 DOI: 10.1039/d0cp04402d] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cinnamate derivatives are very useful as UV protectors in nature and as sunscreen reagents in daily life. They convert harmful UV energy to thermal energy through effective nonradiative decay (NRD) including trans → cis photoisomerization. However, the mechanism is not simple because different photoisomeirzation routes have been observed for different substituted cinnamates. Here, we theoretically examined the substitution effects at the phenyl ring of methylcinnamate (MC), a non-substituted cinnamate, on the electronic structure and the NRD route involving trans → cis isomerization based on time-dependent density functional theory. A systematic reaction pathway search using the single-component artificial force-induced reaction method shows that the very efficient photoisomerization route of MC can be essentially described as "1ππ* (trans) → 1nπ* → T1 (3ππ*) → S0 (trans or cis)". We found that for efficient 1ππ* (trans) → 1nπ* internal conversion (IC), MC should have the substituent at the appropriate position of the phenyl ring to stabilize the highest occupied π orbital. Substitution at the para position of MC slightly lowers the 1ππ* state energy and photoisomerization occurs via a slightly less efficient "1ππ* (trans) → 3nπ* → T1 (3ππ*) → S0 (trans or cis)" pathway. Substitution at the meta or ortho positions of MC significantly lowers the 1ππ* state energy so that the energy barrier of IC (1ππ* → 1nπ*) becomes very high. This substitution leads to a much longer 1ππ* state lifetime than that of MC and para-substituted MC, and a change in the dominant photoisomerization route to "1ππ* (trans) → C[double bond, length as m-dash]C bond twisting on 1ππ* → S0 (trans or cis)". As a whole, the "1ππ* → 1nπ*" IC observed in MC is the most important initial step for the rapid change of UV energy to thermal energy. We also found that the stabilization of the π orbital (i) minimizes the energy gap between 1ππ* and 1nπ* at the 1ππ* minimum and (ii) makes the 0-0 level of 1ππ* higher than 1nπ* as observed in MC. These MC-like relationships between the 1ππ* and 1nπ* energies should be ideal to maximize the "1ππ* → 1nπ*" IC rate constant according to Marcus theory.
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Affiliation(s)
- Shin-Nosuke Kinoshita
- Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
| | - Yu Harabuchi
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan and Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo 001-0021, Japan
| | - Yoshiya Inokuchi
- Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
| | - Satoshi Maeda
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan and Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo 001-0021, Japan
| | - Masahiro Ehara
- SOKENDAI, the Graduate University for Advanced Studies, Myodaiji, Okazaki 444-8585, Japan and Institute for Molecular Science and Research Center for Computational Science, 38, Myodaiji, Okazaki 444-8585, Japan
| | - Kaoru Yamazaki
- Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577, Japan.
| | - Takayuki Ebata
- Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan.
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