26
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Husband JT, Xie Y, Wilks TR, Male L, Torrent-Sucarrat M, Stavros VG, O'Reilly RK. Rigidochromism by imide functionalisation of an aminomaleimide fluorophore. Chem Sci 2021; 12:10550-10557. [PMID: 34447549 PMCID: PMC8356812 DOI: 10.1039/d1sc03307g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 07/06/2021] [Indexed: 12/16/2022] Open
Abstract
Fluorescent dyes that exhibit high solid state quantum yields and sensitivity to the mechanical properties of their local environment are useful for a wide variety of applications, but are limited in chemical diversity. We report a trityl-functionalised maleimide that displays rigidochromic behaviour, becoming highly fluorescent when immobilised in a solid matrix, while displaying negligible fluorescence in solution. Furthermore, the dye's quantum yield is shown to be sensitive to the nature of the surrounding matrix. Computational studies reveal that this behaviour arises from the precise tuning of inter- and intramolecular noncovalent interactions. This work expands the diversity of molecules exhibiting solid state environment sensitivity, and provides important fundamental insights into their design.
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Whittock AL, Auckloo N, Cowden AM, Turner MAP, Woolley JM, Wills M, Corre C, Stavros VG. Exploring the Blueprint of Photoprotection in Mycosporine-like Amino Acids. J Phys Chem Lett 2021; 12:3641-3646. [PMID: 33826340 DOI: 10.1021/acs.jpclett.1c00728] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Microorganisms require protection against the potentially damaging effects of ultraviolet radiation exposure. Photoprotection is, in part, provided by mycosporine-like amino acids (MAAs). Previous reports have proposed that nonradiative decay mediates the impressive photoprotection abilities of MAAs. In this letter, we present the first ultrafast dynamics study of two MAAs, shinorine and porphyra-334. We demonstrate that, in aqueous solution, these MAAs relax along their S1 coordinates toward the S1/S0 conical intersection within a few hundred femtoseconds after photoexcitation and then traverse the conical intersection and vibrationally cool in approximately 1 ps through heat transfer to the solvent. This new insight allows a quintessential component of microbial life to be unraveled and informs the development of molecular photon-to-heat converters for a myriad of applications.
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Abiola TT, Rodrigues NDN, Ho C, Coxon DJL, Horbury MD, Toldo JM, do Casal MT, Rioux B, Peyrot C, Mention MM, Balaguer P, Barbatti M, Allais F, Stavros VG. New Generation UV-A Filters: Understanding Their Photodynamics on a Human Skin Mimic. J Phys Chem Lett 2021; 12:337-344. [PMID: 33353308 DOI: 10.1021/acs.jpclett.0c03004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The sparsity of efficient commercial ultraviolet-A (UV-A) filters is a major challenge toward developing effective broadband sunscreens with minimal human- and eco-toxicity. To combat this, we have designed a new class of Meldrum-based phenolic UV-A filters. We explore the ultrafast photodynamics of coumaryl Meldrum, CMe, and sinapyl Meldrum (SMe), both in an industry-standard emollient and on a synthetic skin mimic, using femtosecond transient electronic and vibrational absorption spectroscopies and computational simulations. Upon photoexcitation to the lowest excited singlet state (S1), these Meldrum-based phenolics undergo fast and efficient nonradiative decay to repopulate the electronic ground state (S0). We propose an initial ultrafast twisted intramolecular charge-transfer mechanism as these systems evolve out of the Franck-Condon region toward an S1/S0 conical intersection, followed by internal conversion to S0 and subsequent vibrational cooling. Importantly, we correlate these findings to their long-term photostability upon irradiation with a solar simulator and conclude that these molecules surpass the basic requirements of an industry-standard UV filter.
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Song Q, Goia S, Yang J, Hall SCL, Staniforth M, Stavros VG, Perrier S. Efficient Artificial Light-Harvesting System Based on Supramolecular Peptide Nanotubes in Water. J Am Chem Soc 2020; 143:382-389. [PMID: 33348987 PMCID: PMC8172009 DOI: 10.1021/jacs.0c11060] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
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Artificial
light-harvesting systems in aqueous media which mimic
nature are of significant importance; however, they are often restrained
by the solubility and the undesired aggregation-caused quenching effect
of the hydrophobic chromophores. Here, we report a generalized strategy
toward the construction of efficient artificial light-harvesting systems
based on supramolecular peptide nanotubes in water. By molecularly
aligning the hydrophobic chromophores along the nanotubes in a slipped
manner, an artificial light-harvesting system with a two-step sequential
Förster resonance energy transfer process is successfully fabricated,
showing an energy transfer efficiency up to 95% and a remarkably high
fluorescence quantum yield of 30%, along with high stability. Furthermore,
the spectral emission could be continuously tuned from blue through
green to orange, as well as outputted as a white light continuum with
a fluorescence quantum yield of 29.9%. Our findings provide a versatile
approach of designing efficient artificial light-harvesting systems
and constructing highly emissive organic materials in aqueous media.
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30
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Woolley JM, Losantos R, Sampedro D, Stavros VG. Computational and experimental characterization of novel ultraviolet filters. Phys Chem Chem Phys 2020; 22:25390-25395. [PMID: 33141123 DOI: 10.1039/d0cp04940a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Many current ultraviolet filters present potential hazards both to humans and to the natural environment. As such there is a new impetus to develop, through intimate characterisation, ultraviolet filters for use in cosmeceuticals. Here we report a new class of organic molecules which have a strong absorption band across the ultraviolet-A and -B regions of the electromagnetic spectrum and high photostability. We have performed ultrafast transient electronic absorption spectroscopy and steady-state spectroscopies, alongside computational studies to track and manipulate photoprotection mechanisms. Our results present a potentially new generation of ultraviolet filters for use in commercial formulations.
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Whittock AL, Turner MAP, Coxon DJL, Woolley JM, Horbury MD, Stavros VG. Reinvestigating the Photoprotection Properties of a Mycosporine Amino Acid Motif. Front Chem 2020; 8:574038. [PMID: 33102444 PMCID: PMC7546825 DOI: 10.3389/fchem.2020.574038] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/26/2020] [Indexed: 12/28/2022] Open
Abstract
With the growing concern regarding commercially available ultraviolet (UV) filters damaging the environment, there is an urgent need to discover new UV filters. A family of molecules called mycosporines and mycosporine-like amino acids (referred to as MAAs collectively) are synthesized by cyanobacteria, fungi and algae and act as the natural UV filters for these organisms. Mycosporines are formed of a cyclohexenone core structure while mycosporine-like amino acids are formed of a cyclohexenimine core structure. To better understand the photoprotection properties of MAAs, we implement a bottom-up approach by first studying a simple analog of an MAA, 3-aminocyclohex-2-en-1-one (ACyO). Previous experimental studies on ACyO using transient electronic absorption spectroscopy (TEAS) suggest that upon photoexcitation, ACyO becomes trapped in the minimum of an S1 state, which persists for extended time delays (>2.5 ns). However, these studies were unable to establish the extent of electronic ground state recovery of ACyO within 2.5 ns due to experimental constraints. In the present studies, we have implemented transient vibrational absorption spectroscopy (as well as complementary TEAS) with Fourier transform infrared spectroscopy and density functional theory to establish the extent of electronic ground state recovery of ACyO within this time window. We show that by 1.8 ns, there is >75% electronic ground state recovery of ACyO, with the remaining percentage likely persisting in the electronic excited state. Long-term irradiation studies on ACyO have shown that a small percentage degrades after 2 h of irradiation, plausibly due to some of the aforementioned trapped ACyO going on to form a photoproduct. Collectively, these studies imply that a base building block of MAAs already displays characteristics of an effective UV filter.
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Krokidi KM, Turner MAP, Pearcy PAJ, Stavros VG. A systematic approach to methyl cinnamate photodynamics. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1811910] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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33
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Baker LA, Staniforth M, Flourat AL, Allais F, Stavros VG. Conservation of ultrafast photoprotective mechanisms with increasing molecular complexity in sinapoyl malate derivatives. Chemphyschem 2020; 21:2006-2011. [PMID: 32638475 PMCID: PMC7586465 DOI: 10.1002/cphc.202000429] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 06/24/2020] [Indexed: 11/09/2022]
Abstract
Sinapoyl malate is a natural plant sunscreen molecule which protects leaves from harmful ultraviolet radiation. Here, the ultrafast dynamics of three sinapoyl malate derivatives, sinapoyl L-dimethyl malate, sinapoyl L-diethyl malate and sinapoyl L-di-t-butyl malate, have been studied using transient electronic absorption spectroscopy, in a dioxane and methanol solvent environment to investigate how well preserved these dynamics remain with increasing molecular complexity. In all cases it was found that, upon photoexcitation, deactivation occurs via a trans-cis isomerisation pathway within ∼20-30 ps. This cis-photoproduct, formed during photodeactivation, is stable and longed-lived for all molecules in both solvents. The incredible levels of conservation of the isomerisation pathway with increased molecular complexity demonstrate the efficacy of these molecules as ultraviolet photoprotectors, even in strongly perturbing solvents. As such, we suggest these molecules might be well-suited for augmentations to further improve their photoprotective efficacy or chemical compatibility with other components of sunscreen mixtures, whilst conserving their underlying photodynamic properties.
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Horbury MD, Turner MAP, Peters JS, Mention M, Flourat AL, Hine NDM, Allais F, Stavros VG. Exploring the Photochemistry of an Ethyl Sinapate Dimer: An Attempt Toward a Better Ultraviolet Filter. Front Chem 2020; 8:633. [PMID: 32850651 PMCID: PMC7399488 DOI: 10.3389/fchem.2020.00633] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 06/17/2020] [Indexed: 11/16/2022] Open
Abstract
The photochemistry and photostability of a potential ultraviolet (UV) radiation filter, dehydrodiethylsinapate, with a broad absorption in the UVA region, is explored utilizing a combination of femtosecond time-resolved spectroscopy and steady-state irradiation studies. The time-resolved measurements show that this UV filter candidate undergoes excited state relaxation after UV absorption on a timescale of ~10 picoseconds, suggesting efficient relaxation. However, steady-state irradiation measurements show degradation under prolonged UV exposure. From a photochemical standpoint, this highlights the importance of considering both the ultrafast and “ultraslow” timescales when designing new potential UV filters.
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Abiola TT, Whittock AL, Stavros VG. Unravelling the Photoprotective Mechanisms of Nature-Inspired Ultraviolet Filters Using Ultrafast Spectroscopy. Molecules 2020; 25:E3945. [PMID: 32872380 PMCID: PMC7504748 DOI: 10.3390/molecules25173945] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/26/2020] [Accepted: 08/27/2020] [Indexed: 02/07/2023] Open
Abstract
There are several drawbacks with the current commercially available ultraviolet (UV) filters used in sunscreen formulations, namely deleterious human and ecotoxic effects. As a result of the drawbacks, a current research interest is in identifying and designing new UV filters. One approach that has been explored in recent years is to use nature as inspiration, which is the focus of this review. Both plants and microorganisms have adapted to synthesize their own photoprotective molecules to guard their DNA from potentially harmful UV radiation. The relaxation mechanism of a molecule after it has been photoexcited can be unravelled by several techniques, the ones of most interest for this review being ultrafast spectroscopy and computational methods. Within the literature, both techniques have been implemented on plant-, and microbial-inspired UV filters to better understand their photoprotective roles in nature. This review aims to explore these findings for both families of nature-inspired UV filters in the hope of guiding the future design of sunscreens.
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Coxon DJL, Staniforth M, Breeze BG, Greenough SE, Goss JP, Monti M, Lloyd-Hughes J, Stavros VG, Newton ME. An Ultrafast Shakedown Reveals the Energy Landscape, Relaxation Dynamics, and Concentration of the N 3VH 0 Defect in Diamond. J Phys Chem Lett 2020; 11:6677-6683. [PMID: 32680426 DOI: 10.1021/acs.jpclett.0c01806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Atomic-scale defects can control the exploitable optoelectronic performance of crystalline materials, and several point defects in diamond are emerging functional components for a range of quantum technologies. Nitrogen and hydrogen are common impurities incorporated into diamond, and there is a family of defects that includes both. The N3VH0 defect is a lattice vacancy where three nearest neighbor carbon atoms are replaced with nitrogen atoms and a hydrogen is bonded to the remaining carbon. It is regularly observed in natural and high-temperature annealed synthetic diamond and gives rise to prominent absorption features in the mid-infrared. Here, we combine time- and spectrally resolved infrared absorption spectroscopy to yield unprecedented insight into the N3VH0 defect's vibrational dynamics following infrared excitation of the C-H stretch. In doing so, we gain fundamental information about the energies of quantized vibrational states and corroborate our results with theory. We map out, for the first time, energy relaxation pathways, which include multiphonon relaxation processes and anharmonic coupling to the C-H bend mode. These advances provide new routes to quantify and probe atomic-scale defects.
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37
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Holt EL, Krokidi KM, Turner MAP, Mishra P, Zwier TS, Rodrigues NDN, Stavros VG. Insights into the photoprotection mechanism of the UV filter homosalate. Phys Chem Chem Phys 2020; 22:15509-15519. [DOI: 10.1039/d0cp02610g] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Homosalate has been found to exhibit favourable photophysics for inclusion in sunscreens, using a combination of spectroscopic and computational approaches.
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38
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Liarou E, Staniforth M, Town JS, Marathianos A, Grypioti M, Li Y, Chang Y, Efstathiou S, Hancox E, Wemyss AM, Wilson P, Jones BA, Aljuaid M, Stavros VG, Haddleton DM. UV irradiation of Cu-based complexes with aliphatic amine ligands as used in living radical polymerization. Eur Polym J 2020. [DOI: 10.1016/j.eurpolymj.2019.109388] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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39
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Abstract
Mycosporine-like amino acids have long been known as a natural form of photoprotection for fungi and cyanobacteria. This review will highlight the key time-resolved experimental and theoretical techniques unravelling their photochemistry and photophysics, and directly link this to their use in commercial skin-care products, namely as sunscreen filters. Three case studies have been selected, each having aided advancement in this burgeoning field of research. We discuss these studies in the context of photoprotection and conclude by evaluating the necessary future steps towards translating the photochemistry and photophysics insight of these nature derived sunscreen filters to commercial application.
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40
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Horbury MD, Holt EL, Mouterde LMM, Balaguer P, Cebrián J, Blasco L, Allais F, Stavros VG. Towards symmetry driven and nature inspired UV filter design. Nat Commun 2019; 10:4748. [PMID: 31628301 PMCID: PMC6802189 DOI: 10.1038/s41467-019-12719-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 09/26/2019] [Indexed: 12/13/2022] Open
Abstract
In plants, sinapate esters offer crucial protection from the deleterious effects of ultraviolet radiation exposure. These esters are a promising foundation for designing UV filters, particularly for the UVA region (400 – 315 nm), where adequate photoprotection is currently lacking. Whilst sinapate esters are highly photostable due to a cis-trans (and vice versa) photoisomerization, the cis-isomer can display increased genotoxicity; an alarming concern for current cinnamate ester-based human sunscreens. To eliminate this potentiality, here we synthesize a sinapate ester with equivalent cis- and trans-isomers. We investigate its photostability through innovative ultrafast spectroscopy on a skin mimic, thus modelling the as close to true environment of sunscreen formulas. These studies are complemented by assessing endocrine disruption activity and antioxidant potential. We contest, from our results, that symmetrically functionalized sinapate esters may show exceptional promise as nature-inspired UV filters in next generation sunscreen formulations. Sinapate esters are promising nature-inspired sunscreen and antioxidant agents but their photoisomerization may lead to ineffective or harmful species. Here the authors propose a symmetric ester with indistinguishable trans and cis isomers and prove its effectiveness by optical spectroscopies on a skin mimic.
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41
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Holt EL, Stavros VG. Applications of ultrafast spectroscopy to sunscreen development, from first principles to complex mixtures. INT REV PHYS CHEM 2019. [DOI: 10.1080/0144235x.2019.1663062] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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42
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Turner MAP, Turner RJ, Horbury MD, Hine NDM, Stavros VG. Examining solvent effects on the ultrafast dynamics of catechol. J Chem Phys 2019; 151:084305. [PMID: 31470726 DOI: 10.1063/1.5116312] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We consider the effect of a polar, hydrogen bond accepting, solvent environment on the excited state decay of catechol following excitation to its first excited singlet state (S1). A comparison of Fourier transform infrared spectroscopy and explicit-solvent ab initio frequency prediction suggests that 5 mM catechol in acetonitrile is both nonaggregated and in its "closed" conformation, contrary to what has been previously proposed. Using ultrafast transient absorption spectroscopy, we then demonstrate the effects of aggregation on the photoexcited S1 lifetime: at 5 mM catechol (nonaggregated) in acetonitrile, the S1 lifetime is 713 ps. In contrast at 75 mM catechol in acetonitrile, the S1 lifetime increases to 1700 ps. We attribute this difference to aggregation effects on the excited-state landscape. This work has shown that explicit-solvent methodology is key when calculating the vibrational frequencies of molecules in a strongly interacting solvent. Combining this with highly complementary steady-state and transient absorption spectroscopy enables us to gain key dynamical insights into how a prominent eumelanin building block behaves when in polar, hydrogen bond accepting solvents both as a monomer and as an aggregated species.
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43
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Symonds CC, Makhov DV, Cole-Filipiak NC, Green JA, Stavros VG, Shalashilin DV. Ultrafast photodissociation dynamics of pyrazole, imidazole and their deuterated derivatives using ab initio multiple cloning. Phys Chem Chem Phys 2019; 21:9987-9995. [DOI: 10.1039/c9cp00039a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Fully quantum nonadiabatic dynamics calculation of photodissociation of azoles shows good agreement with experiment and foreshadows the predictive ability of the method.
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44
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Woolley JM, Peters JS, Turner MAP, Clarkson GJ, Horbury MD, Stavros VG. The role of symmetric functionalisation on photoisomerisation of a UV commercial chemical filter. Phys Chem Chem Phys 2019; 21:14350-14356. [DOI: 10.1039/c8cp06536e] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Photoisomerisation has been shown to be an efficient excited-state relaxation mechanism for a variety of nature-based and artificial-based molecular systems.
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45
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Green JA, Makhov DV, Cole-Filipiak NC, Symonds C, Stavros VG, Shalashilin DV. Ultrafast photodissociation dynamics of 2-ethylpyrrole: adding insight to experiment with ab initio multiple cloning. Phys Chem Chem Phys 2019; 21:3832-3841. [DOI: 10.1039/c8cp06359a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fully quantum nonadiabatic dynamics calculation of 2-ethylpyrrole photodissociation shows the experimentally obtained ultrafast time-constant has two components.
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46
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Cole-Filipiak NC, Stavros VG. New insights into the dissociation dynamics of methylated anilines. Phys Chem Chem Phys 2019; 21:14394-14406. [DOI: 10.1039/c8cp07061j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Combined time-resolved photoelectron spectroscopy and photofragment imaging supports a possible valence-to-Rydberg decay mechanism in methylated anilines.
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47
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Rodrigues ND, Cole-Filipiak NC, Turner MA, Krokidi K, Thornton GL, Richings GW, Hine ND, Stavros VG. Substituent position effects on sunscreen photodynamics: A closer look at methyl anthranilate. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.08.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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48
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Rodrigues NDN, Staniforth M, Young JD, Peperstraete Y, Cole-Filipiak NC, Gord JR, Walsh PS, Hewett DM, Zwier TS, Stavros VG. Towards elucidating the photochemistry of the sunscreen filter ethyl ferulate using time-resolved gas-phase spectroscopy. Faraday Discuss 2018; 194:709-729. [PMID: 27711798 DOI: 10.1039/c6fd00079g] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast time-resolved ion yield (TR-IY) and velocity map imaging spectroscopies are employed to reveal the relaxation dynamics after photoexcitation in ethyl 4-hydroxy-3-methoxycinnamate (ethyl ferulate, EF), an active ingredient in commercially available sunscreens. In keeping with a bottom-up strategy, the building blocks of EF, 2-methoxy-4-vinylphenol (MVP) and 4-hydroxy-3-methoxycinnamyl alcohol (coniferyl alcohol, ConA), were also studied to assist in our understanding of the dynamics of EF as we build up in molecular complexity. In contrast to the excited state dynamics of MVP and ConA, which are described by a single time constant (>900 ps), the dynamics of EF are described by three time constants (15 ± 4 ps, 148 ± 47 ps, and >900 ps). A mechanism is proposed involving internal conversion (IC) between the initially excited S1(11ππ*) and S2(11nπ*) states followed by intramolecular vibrational redistribution (IVR) on both states, in competition with intersystem crossing onto neighbouring triplet states (15 ± 4 ps). IVR and IC within the triplet manifold then ensues (148 ± 47 ps) to populate a low-lying triplet state (>900 ps). Importantly, the fluorescence spectrum of EF at the S1 origin, along with the associated lifetime (6.9 ± 0.1 ns), suggests that population is trapped, during initial IVR, on the S1(11ππ*) state. This serves to demonstrate the complex, competing dynamics in this sunscreen filter molecule.
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49
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Woolley JM, Staniforth M, Horbury MD, Richings GW, Wills M, Stavros VG. Unravelling the Photoprotection Properties of Mycosporine Amino Acid Motifs. J Phys Chem Lett 2018; 9:3043-3048. [PMID: 29751729 DOI: 10.1021/acs.jpclett.8b00921] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Photoprotection from harmful ultraviolet (UV) radiation exposure is a key problem in modern society. Mycosporine-like amino acids found in fungi, cyanobacteria, macroalgae, phytoplankton, and animals are already presenting a promising form of natural photoprotection in sunscreen formulations. Using time-resolved transient electronic absorption spectroscopy and guided by complementary ab initio calculations, we help to unravel how the core structures of these molecules perform under UV irradiation. Through such detailed insight into the relaxation mechanisms of these ubiquitous molecules, we hope to inspire new thinking in developing next-generation photoprotective molecules.
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50
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Baker LA, Staniforth M, Flourat AL, Allais F, Stavros VG. Gas-Solution Phase Transient Absorption Study of the Plant Sunscreen Derivative Methyl Sinapate. CHEMPHOTOCHEM 2018. [DOI: 10.1002/cptc.201800060] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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