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Vernooij RR, Joshi T, Horbury MD, Graham B, Izgorodina EI, Stavros VG, Sadler PJ, Spiccia L, Wood BR. Spectroscopic Studies on Photoinduced Reactions of the Anticancer Prodrug, trans,trans,trans-[Pt(N 3 ) 2 (OH) 2 (py) 2 ]. Chemistry 2018; 24:5790-5803. [PMID: 29314368 PMCID: PMC5947305 DOI: 10.1002/chem.201705349] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Indexed: 02/05/2023]
Abstract
The photodecomposition mechanism of trans,trans,trans-[Pt(N3 )2 (OH)2 (py)2 ] (1, py=pyridine), an anticancer prodrug candidate, was probed using complementary Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), transient electronic absorption, and UV/Vis spectroscopy. Data fitting using Principal Component Analysis (PCA) and Multi-Curve Resolution Alternating Least Squares, suggests the formation of a trans-[Pt(N3 )(py)2 (OH/H2 O)] intermediate and trans-[Pt(py)2 (OH/H2 O)2 ] as the final product upon 420 nm irradiation of 1 in water. Rapid disappearance of the hydroxido ligand stretching vibration upon irradiation is correlated with a -10 cm-1 shift to the antisymmetric azido vibration, suggesting a possible second intermediate. Experimental proof of subsequent dissociation of azido ligands from platinum is presented, in which at least one hydroxyl radical is formed in the reduction of PtIV to PtII . Additionally, the photoinduced reaction of 1 with the nucleotide 5'-guanosine monophosphate (5'-GMP) was comprehensively studied, and the identity of key photoproducts was assigned with the help of ATR-FTIR spectroscopy, mass spectrometry, and density functional theory calculations. The identification of marker bands for some of these photoproducts (e.g., trans-[Pt(N3 )(py)2 (5'-GMP)] and trans-[Pt(py)2 (5'-GMP)2 ]) will aid elucidation of the chemical and biological mechanism of anticancer action of 1. In general, these studies demonstrate the potential of vibrational spectroscopic techniques as promising tools for studying such metal complexes.
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Vernooij RR, Joshi T, Horbury MD, Graham B, Izgorodina EI, Stavros VG, Sadler PJ, Spiccia L, Wood BR. Front Cover: Spectroscopic Studies on Photoinduced Reactions of the Anticancer Prodrug, trans,trans,trans
-[Pt(N 3
) 2
(OH) 2
(py) 2
] (Chem. Eur. J. 22/2018). Chemistry 2018. [DOI: 10.1002/chem.201800161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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53
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Vernooij RR, Joshi T, Horbury MD, Graham B, Izgorodina EI, Stavros VG, Sadler PJ, Spiccia L, Wood BR. Spectroscopic Studies on Photoinduced Reactions of the Anticancer Prodrug, trans,trans,trans
-[Pt(N 3
) 2
(OH) 2
(py) 2
]. Chemistry 2018. [DOI: 10.1002/chem.201800162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Baker LA, Marchetti B, Karsili TNV, Stavros VG, Ashfold MNR. Photoprotection: extending lessons learned from studying natural sunscreens to the design of artificial sunscreen constituents. Chem Soc Rev 2018; 46:3770-3791. [PMID: 28580469 DOI: 10.1039/c7cs00102a] [Citation(s) in RCA: 106] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Evolution has ensured that plants and animals have developed effective protection mechanisms against the potentially harmful effects of incident ultraviolet radiation (UVR). Tanning is one such mechanism in humans, but tanning only occurs post-exposure to UVR. Hence, there is ever growing use of commercial sunscreens to pre-empt overexposure to UVR. Key requirements for any chemical filter molecule used in such a photoprotective capacity include a large absorption cross-section in the UV-A and UV-B spectral regions and the availability of one or more mechanisms whereby the absorbed photon energy can be dissipated without loss of the molecular integrity of the chemical filter. Here we summarise recent experimental (mostly ultrafast pump-probe spectroscopy studies) and computational progress towards unravelling various excited state decay mechanisms that afford the necessary photostability in chemical filters found in nature and those used in commercial sunscreens. We also outline ways in which a better understanding of the photophysics and photochemistry of sunscreen molecules selected by nature could aid the design of new and improved commercial sunscreen formulations.
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Abstract
Despite the pivotal role of ultraviolet (UV) radiation in sustaining life on Earth, overexposure to this type of radiation can have catastrophic effects, such as skin cancer. Sunscreens, the most common form of artificial protection against such harmful effects, absorb UV radiation before it reaches vulnerable skin cells. Absorption of UV radiation prompts ultrafast molecular events in sunscreen molecules which, ideally, would allow for fast and safe dissipation of the excess energy. However, our knowledge of these mechanisms remains limited. In this article, we will review recent advances in the field of ultrafast photodynamics (light induced molecular processes occurring within femtoseconds, fs, 10-15 s to picoseconds, ps, 10-12 s) of sunscreens. We follow a bottom-up approach to common sunscreen active ingredients, analysing any emerging trends from the current literature on the subject. Moreover, we will identify the main questions that remain unanswered, pinpoint some of the main challenges and finally comment on the outlook of this exciting field of research.
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Horbury MD, Quan WD, Flourat AL, Allais F, Stavros VG. Elucidating nuclear motions in a plant sunscreen during photoisomerization through solvent viscosity effects. Phys Chem Chem Phys 2018; 19:21127-21131. [PMID: 28749499 DOI: 10.1039/c7cp04070a] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We explore the effects of solvent viscosity on the trans-cis photoisomerization of sinapoyl malate, which is utilized as a sunscreen molecule in plants. Our results demonstrate that viscosity has a significant effect on the timescale for isomerization, providing insight into the nuclear motions involved. The ramifications of these findings are discussed with reference to sinapoyl malate's in vivo photoprotection properties.
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Staniforth M, Quan WD, Karsili TNV, Baker LA, O’Reilly RK, Stavros VG. First Step toward a Universal Fluorescent Probe: Unravelling the Photodynamics of an Amino–Maleimide Fluorophore. J Phys Chem A 2017; 121:6357-6365. [DOI: 10.1021/acs.jpca.7b04702] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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58
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Baker LA, Clark SL, Habershon S, Stavros VG. Ultrafast Transient Absorption Spectroscopy of the Sunscreen Constituent Ethylhexyl Triazone. J Phys Chem Lett 2017; 8:2113-2118. [PMID: 28437110 DOI: 10.1021/acs.jpclett.7b00633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ultrafast photoprotection mechanisms in operation in ethylhexyl triazone (EHT, octyl triazone), an approved ultraviolet-B (UV-B) chemical filter for commercial sunscreens, remain elusive, with a notable absence of ultrafast time-resolved measurements. These large organic molecules are of increasing interest as they are suspected to be less likely to penetrate the skin than some of the smaller approved filters, thereby reducing the possible adverse effects from sunscreen products. We apply femtosecond transient absorption spectroscopy with electronic structure calculations to unravel the complete photodeactivation mechanism that EHT undergoes after UV-B irradiation. We propose that this involves ultrafast internal conversion of the initially photoexcited n1ππ* state that couples to the ground state via a 11ππ*/S0 conical intersection, enabling multiple absorption and recovery cycles, as one would anticipate from a highly efficient filter. We also observe long-lived photoproducts which, based on previous studies along with present electronic structure calculations, we attribute to trapped excited populations in the S1 and T1 states.
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Horbury MD, Baker LA, Rodrigues ND, Quan WD, Stavros VG. Photoisomerization of ethyl ferulate: A solution phase transient absorption study. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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60
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Cole-Filipiak NC, Staniforth M, d. N. Rodrigues N, Peperstraete Y, Stavros VG. Ultrafast Dissociation Dynamics of 2-Ethylpyrrole. J Phys Chem A 2017; 121:969-976. [DOI: 10.1021/acs.jpca.6b12228] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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61
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Pitto-Barry A, Geraki K, Horbury MD, Stavros VG, Mosselmans JFW, Walton RI, Sadler PJ, Barry NPE. Controlled fabrication of osmium nanocrystals by electron, laser and microwave irradiation and characterisation by microfocus X-ray absorption spectroscopy. Chem Commun (Camb) 2017; 53:12898-12901. [DOI: 10.1039/c7cc07133g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Osmium nanocrystals are fabricatedvia3 methods and characterised by XAS, revealing different surface oxidation and metallicities depending on their fabrication technique.
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Smith NA, Zhang P, Greenough SE, Horbury MD, Clarkson GJ, McFeely D, Habtemariam A, Salassa L, Stavros VG, Dowson CG, Sadler PJ. Combatting AMR: photoactivatable ruthenium(ii)-isoniazid complex exhibits rapid selective antimycobacterial activity. Chem Sci 2017; 8:395-404. [PMID: 28451184 PMCID: PMC5365061 DOI: 10.1039/c6sc03028a] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 08/11/2016] [Indexed: 12/12/2022] Open
Abstract
The novel photoactive ruthenium(ii) complex cis-[Ru(bpy)2(INH)2][PF6]2 (1·2PF6, INH = isoniazid) was designed to incorporate the anti-tuberculosis drug, isoniazid, that could be released from the Ru(ii) cage by photoactivation with visible light. In aqueous solution, 1 rapidly released two equivalents of isoniazid and formed the photoproduct cis-[Ru(bpy)2(H2O)2]2+ upon irradiation with 465 nm blue light. We screened for activity against bacteria containing the three major classes of cell envelope: Gram-positive Bacillus subtilis, Gram-negative Escherichia coli, and Mycobacterium smegmatis in vitro using blue and multi-colored LED multi-well arrays. Complex 1 is inactive in the dark, but when photoactivated is 5.5× more potent towards M. smegmatis compared to the clinical drug isoniazid alone. Complementary pump-probe spectroscopy measurements along with density functional theory calculations reveal that the mono-aqua product is formed in <500 ps, likely facilitated by a 3MC state. Importantly, complex 1 is highly selective in killing mycobacteria versus normal human cells, towards which it is relatively non-toxic. This work suggests that photoactivatable prodrugs such as 1 are potentially powerful new agents in combatting the global problem of antibiotic resistance.
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Orr-Ewing AJ, Kornilov O, Sølling TI, Keane T, Minitti MP, Wörner HJ, Schalk O, Roberts GM, Minns RS, Milne CJ, Miseikis L, Penfold TJ, Miller RJD, Domcke W, Centurion M, Ueda K, Weber PM, Gessner O, Neumark DM, Stolow A, Yano J, Mukamel S, Stavros VG. Vibrational and condensed phase dynamics: general discussion. Faraday Discuss 2016; 194:747-775. [PMID: 27901160 DOI: 10.1039/c6fd90073a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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64
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Baker LA, Greenough SE, Stavros VG. A Perspective on the Ultrafast Photochemistry of Solution-Phase Sunscreen Molecules. J Phys Chem Lett 2016; 7:4655-4665. [PMID: 27791379 DOI: 10.1021/acs.jpclett.6b02104] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Sunscreens are one of the most common ways of providing on-demand additional photoprotection to the skin. Ultrafast transient absorption spectroscopy has recently proven to be an invaluable tool in understanding how the components of commercial sunscreen products display efficient photoprotection. Important examples of how this technique has unravelled the photodynamics of common components are given in this Perspective, and some of the remaining unanswered questions are discussed.
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Rodrigues NDN, Staniforth M, Stavros VG. Photophysics of sunscreen molecules in the gas phase: a stepwise approach towards understanding and developing next-generation sunscreens. Proc Math Phys Eng Sci 2016; 472:20160677. [PMID: 27956888 PMCID: PMC5134319 DOI: 10.1098/rspa.2016.0677] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 10/24/2016] [Indexed: 12/22/2022] Open
Abstract
The relationship between exposure to ultraviolet (UV) radiation and skin cancer urges the need for extra photoprotection, which is presently provided by widespread commercially available sunscreen lotions. Apart from having a large absorption cross section in the UVA and UVB regions of the electromagnetic spectrum, the chemical absorbers in these photoprotective products should also be able to dissipate the excess energy in a safe way, i.e. without releasing photoproducts or inducing any further, harmful, photochemistry. While sunscreens are tested for both their photoprotective capability and dermatological compatibility, phenomena occurring at the molecular level upon absorption of UV radiation are largely overlooked. To date, there is only a limited amount of information regarding the photochemistry and photophysics of these sunscreen molecules. However, a thorough understanding of the intrinsic mechanisms by which popular sunscreen molecular constituents dissipate excess energy has the potential to aid in the design of more efficient, safer sunscreens. In this review, we explore the potential of using gas-phase frequency- and time-resolved spectroscopies in an effort to better understand the photoinduced excited-state dynamics, or photodynamics, of sunscreen molecules. Complementary computational studies are also briefly discussed. Finally, the future outlook of expanding these gas-phase studies into the solution phase is considered.
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66
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Baker LA, Grosvenor LC, Ashfold MN, Stavros VG. Ultrafast photophysical studies of a multicomponent sunscreen: Oxybenzone–titanium dioxide mixtures. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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67
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Quan WD, Pitto-Barry A, Baker LA, Stulz E, Napier R, O'Reilly RK, Stavros VG. Retaining individualities: the photodynamics of self-ordering porphyrin assemblies. Chem Commun (Camb) 2016; 52:1938-41. [PMID: 26680651 PMCID: PMC4720934 DOI: 10.1039/c5cc09095d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Retained photochemical properties – a simple porphyrin–polyDMA conjugate with the ability to self assemble into large (∼1 μm) vesicles in water. The photodynamics are remarkably preserved despite the extensive aggregation.
The retention of photochemical properties of individual chromophores is a key feature of biological light harvesting complexes. This is achieved despite extensive aggregation of the chromophores, which in synthetic chromophore assemblies often yields a change in spectral characteristics. As an alternative approach towards mimicking biological light harvesting complexes, we report the synthesis of porphyrin assemblies which retained the photochemical properties of the individual chromophore units despite their substantial aggregation. These new materials highlight a new bottom-up approach towards the design and understanding of more complex biomimetic and naturally occurring biological systems.
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Baker LA, Stavros VG. Observing and understanding the ultrafast photochemistry in small molecules: applications to sunscreens. Sci Prog 2016; 99:282-311. [PMID: 28742490 PMCID: PMC10365382 DOI: 10.3184/003685016x14684992086383] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this review, we discuss the importance of biological and artificial photoprotection against overexposure to harmful ultraviolet radiation. Transient electronic and transient vibrational absorption spectroscopies are highlighted as important tools in understanding the energy transfer in small molecules, with a focus on the application to commercial sunscreens with representative examples given. Oxybenzone, a common ingredient in commercial sunscreens and sinapoyl malate, a biological sunscreen in plant leaves are presented as case studies.
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Horbury MD, Baker LA, Quan WD, Greenough SE, Stavros VG. Photodynamics of potent antioxidants: ferulic and caffeic acids. Phys Chem Chem Phys 2016; 18:17691-7. [PMID: 27310931 DOI: 10.1039/c6cp01595f] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The dynamics of ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid) and caffeic acid (3-(3,4-dihydroxyphenyl)-2-propenoic acid) in acetonitrile, dioxane and water at pH 2.2 following photoexcitation to the first excited singlet state are reported. These hydroxycinnamic acids display both strong ultraviolet absorption and potent antioxidant activity, making them promising sunscreen components. Ferulic and caffeic acids have previously been shown to undergo trans-cis photoisomerization via irradiation studies, yet time-resolved measurements were unable to observe formation of the cis-isomer. In the present study, we are able to observe the formation of the cis-isomer as well as provide timescales of relaxation following initial photoexcitation.
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Baker LA, Horbury MD, Stavros VG. Ultrafast photoprotective properties of the sunscreening agent octocrylene. OPTICS EXPRESS 2016; 24:10700-10709. [PMID: 27409891 DOI: 10.1364/oe.24.010700] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Today octocrylene is one of the most common molecules included in commercially available sunscreens. It provides broadband photoprotection for the skin from incident UV-A and UV-B radiation of the solar spectrum. In order to understand how octocrylene fulfils its role as a sunscreening agent, femtosecond pump-probe transient electronic UV-visible absorption spectroscopy is utilised to investigate the ultrafastnonradiative relaxation mechanism of octocrylene in cyclohexane or methanol after UV-B photoexcitation. The data presented clearly shows that UV-B photoexcited octocrylene exhibits ultrafast-nonradiative relaxation mechanisms to repopulate its initial ground state within a few picoseconds, which, at the very least, photophysically justifies its wide spread inclusion in commercial sunscreens.
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71
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Ingle RA, Karsili TNV, Dennis GJ, Staniforth M, Stavros VG, Ashfold MNR. Extreme population inversion in the fragments formed by UV photoinduced S-H bond fission in 2-thiophenethiol. Phys Chem Chem Phys 2016; 18:11401-10. [PMID: 27056403 DOI: 10.1039/c6cp01593j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
H atom loss following near ultraviolet photoexcitation of gas phase 2-thiophenethiol molecules has been studied experimentally, by photofragment translational spectroscopy (PTS) methods, and computationally, by ab initio electronic structure calculations. The long wavelength (277.5 ≥ λ(phot) ≥ 240 nm) PTS data are consistent with S-H bond fission after population of the first (1)πσ* state. The partner thiophenethiyl (R) radicals are formed predominantly in their first excited Ã(2)A' state, but assignment of a weak signal attributable to H + R(X˜(2)A'') products allows determination of the S-H bond strength, D0 = 27,800 ± 100 cm(-1) and the Ã-X˜ state splitting in the thiophenethiyl radical (ΔE = 3580 ± 100 cm(-1)). The deduced population inversion between the à and X˜ states of the radical reflects the non-planar ground state geometry (wherein the S-H bond is directed near orthogonal to the ring plane) which, post-photoexcitation, is unable to planarise sufficiently prior to bond fission. This dictates that the dissociating molecules follow the adiabatic fragmentation pathway to electronically excited radical products. π* ← π absorption dominates at shorter excitation wavelengths. Coupling to the same (1)πσ* potential energy surface (PES) remains the dominant dissociation route, but a minor yield of H atoms attributable to a rival fragmentation pathway is identified. These products are deduced to arise via unimolecular decay following internal conversion to the ground (S0) state PES via a conical intersection accessed by intra-ring C-S bond extension. The measured translational energy disposal shows a more striking change once λ(phot) ≤ 220 nm. Once again, however, the dominant decay pathway is deduced to be S-H bond fission following coupling to the (1)πσ* PES but, in this case, many of the evolving molecules are deduced to have sufficiently near-planar geometries to allow passage through the conical intersection at extended S-H bond lengths and dissociation to ground (X˜) state radical products. The present data provide no definitive evidence that complete ring opening can compete with fast S-H bond fission following near UV photoexcitation of 2-thiophenethiol.
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Stavros VG, Verlet JRR. Gas-Phase Femtosecond Particle Spectroscopy: A Bottom-Up Approach to Nucleotide Dynamics. Annu Rev Phys Chem 2016; 67:211-32. [PMID: 26980306 DOI: 10.1146/annurev-physchem-040215-112428] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We summarize how gas-phase ultrafast charged-particle spectroscopy has been used to provide an understanding of the photophysics of DNA building blocks. We focus on adenine and discuss how, following UV excitation, specific interactions determine the fates of its excited states. The dynamics can be probed using a systematic bottom-up approach that provides control over these interactions and that allows ever-larger complexes to be studied. Starting from a chromophore in adenine, the excited state decay mechanisms of adenine and chemically substituted or clustered adenine are considered and then extended to adenosine mono-, di-, and trinucleotides. We show that the gas-phase approach can offer exquisite insight into the dynamics observed in aqueous solution, but we also highlight stark differences. An outlook is provided that discusses some of the most promising developments in this bottom-up approach.
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Mabire AB, Robin MP, Quan WD, Willcock H, Stavros VG, O'Reilly RK. Aminomaleimide fluorophores: a simple functional group with bright, solvent dependent emission. Chem Commun (Camb) 2016; 51:9733-6. [PMID: 25985397 PMCID: PMC4540011 DOI: 10.1039/c5cc02908b] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Amino-substituted maleimides form a new class of highly emissive compounds, with large Stokes shifts (>100 nm) and high quantum yields (up to ∼60%).
Amino-substituted maleimides form a new class of highly emissive compounds, with large Stokes shifts (>100 nm) and high quantum yields (up to ∼60%). Emission is responsive to the maleimide's environment with both a red-shift, and quenching, observed in protic polar solvents. Aminomaleimides are easily functionalised, providing a versatile fluorescent probe.
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Greenough SE, Horbury MD, Smith NA, Sadler PJ, Paterson MJ, Stavros VG. Excited-State Dynamics of a Two-Photon-Activatable Ruthenium Prodrug. Chemphyschem 2016; 17:221-4. [PMID: 26632426 PMCID: PMC4797363 DOI: 10.1002/cphc.201501075] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Indexed: 11/16/2022]
Abstract
We present a new approach to investigate how the photodynamics of an octahedral ruthenium(II) complex activated through two-photon absorption (TPA) differ from the equivalent complex activated through one-photon absorption (OPA). We photoactivated a Ru(II) polypyridyl complex containing bioactive monodentate ligands in the photodynamic therapy window (620-1000 nm) by using TPA and used transient UV/Vis absorption spectroscopy to elucidate its reaction pathways. Density functional calculations allowed us to identify the nature of the initially populated states and kinetic analysis recovers a photoactivation lifetime of approximately 100 ps. The dynamics displayed following TPA or OPA are identical, showing that TPA prodrug design may use knowledge gathered from the more numerous and easily conducted OPA studies.
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Baker LA, Horbury MD, Greenough SE, Allais F, Walsh PS, Habershon S, Stavros VG. Ultrafast Photoprotecting Sunscreens in Natural Plants. J Phys Chem Lett 2016; 7:56-61. [PMID: 26654715 DOI: 10.1021/acs.jpclett.5b02474] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We explore the ultrafast photoprotective properties of a series of sinapic acid derivatives in a range of solvents, utilizing femtosecond transient electronic absorption spectroscopy. We find that a primary relaxation mechanism displayed by the plant sunscreen sinapoyl malate and other related molecular species may be understood as a multistep process involving internal conversion of the initially photoexcited 1(1)ππ* state along a trans-cis photoisomerization coordinate, leading to the repopulation of the original trans ground-state isomer or the formation of a stable cis isomer.
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