1
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Figueira Nunes JP, Ibele LM, Pathak S, Attar AR, Bhattacharyya S, Boll R, Borne K, Centurion M, Erk B, Lin MF, Forbes RJG, Goff N, Hansen CS, Hoffmann M, Holland DMP, Ingle RA, Luo D, Muvva SB, Reid AH, Rouzée A, Rudenko A, Saha SK, Shen X, Venkatachalam AS, Wang X, Ware MR, Weathersby SP, Wilkin K, Wolf TJA, Xiong Y, Yang J, Ashfold MNR, Rolles D, Curchod BFE. Monitoring the Evolution of Relative Product Populations at Early Times during a Photochemical Reaction. J Am Chem Soc 2024; 146:4134-4143. [PMID: 38317439 PMCID: PMC10870701 DOI: 10.1021/jacs.3c13046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/10/2024] [Accepted: 01/10/2024] [Indexed: 02/07/2024]
Abstract
Identifying multiple rival reaction products and transient species formed during ultrafast photochemical reactions and determining their time-evolving relative populations are key steps toward understanding and predicting photochemical outcomes. Yet, most contemporary ultrafast studies struggle with clearly identifying and quantifying competing molecular structures/species among the emerging reaction products. Here, we show that mega-electronvolt ultrafast electron diffraction in combination with ab initio molecular dynamics calculations offer a powerful route to determining time-resolved populations of the various isomeric products formed after UV (266 nm) excitation of the five-membered heterocyclic molecule 2(5H)-thiophenone. This strategy provides experimental validation of the predicted high (∼50%) yield of an episulfide isomer containing a strained three-membered ring within ∼1 ps of photoexcitation and highlights the rapidity of interconversion between the rival highly vibrationally excited photoproducts in their ground electronic state.
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Affiliation(s)
| | - Lea Maria Ibele
- CNRS,
Institut de Chimie Physique UMR8000, Université
Paris-Saclay, Orsay, 9140, France
| | - Shashank Pathak
- J.R.
Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, United States
| | - Andrew R. Attar
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Surjendu Bhattacharyya
- J.R.
Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, United States
| | | | - Kurtis Borne
- J.R.
Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, United States
| | - Martin Centurion
- University
of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
| | - Benjamin Erk
- Deutsches
Elektronen Synchrotron DESY, Hamburg, 22607, Germany
| | - Ming-Fu Lin
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Ruaridh J. G. Forbes
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Nathan Goff
- Brown University, Providence, Rhode Island 02912, United States
| | | | - Matthias Hoffmann
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | | | - Rebecca A. Ingle
- Department
of Chemistry, University College London, London, WC1H 0AJ, U.K.
| | - Duan Luo
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Sri Bhavya Muvva
- University
of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
| | - Alexander H. Reid
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | | | - Artem Rudenko
- J.R.
Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, United States
| | - Sajib Kumar Saha
- University
of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
| | - Xiaozhe Shen
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Anbu Selvam Venkatachalam
- J.R.
Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, United States
| | - Xijie Wang
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Matt R. Ware
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | | | - Kyle Wilkin
- University
of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
| | - Thomas J. A. Wolf
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
- Stanford
PULSE Institute, SLAC National Accelerator
Laboratory, Menlo
Park, California 94025, United States
| | - Yanwei Xiong
- University
of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
| | - Jie Yang
- SLAC
National Accelerator Laboratory, Menlo Park, California 94025, United States
| | | | - Daniel Rolles
- J.R.
Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506, United States
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2
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Garner SM, Haugen EA, Leone SR, Neuscamman E. Spin Coupling Effect on Geometry-Dependent X-Ray Absorption of Diradicals. J Am Chem Soc 2024; 146:2387-2397. [PMID: 38235992 DOI: 10.1021/jacs.3c08002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
We theoretically investigate the influence of diradical electron spin coupling on the time-resolved X-ray absorption spectra of the photochemical ring opening of furanone. We predict geometry-dependent carbon K-edge signals involving transitions from core orbitals to both singly and unoccupied molecular orbitals. The most obvious features of the ring opening come from the carbon atom directly involved in the bond breaking through its transition to both the newly formed singly occupied and the available lowest unoccupied molecular orbitals (SOMO and LUMO, respectively). In addition to this primary feature, the singlet spin coupling of four unpaired electrons that arises in the core-to-LUMO states creates additional geometry dependence in some spectral features with both oscillator strengths and relative excitation energies varying observably as a function of the ring opening. We attribute this behavior to a spin-occupancy-induced selection rule, which occurs when singlet spin coupling is enforced in the diradical state. Notably, one of these geometry-sensitive core-to-LUMO transitions excites core electrons from a backbone carbon not involved in the bond breaking, providing a novel nonlocal X-ray probe of chemical dynamics arising from electron spin coupling.
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Affiliation(s)
- Scott M Garner
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Eric A Haugen
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Stephen R Leone
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Physics, University of California, Berkeley, California 94720, United States
| | - Eric Neuscamman
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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3
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Ashfold MNR, Kim SK. Non-Born-Oppenheimer effects in molecular photochemistry: an experimental perspective. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2022; 380:20200376. [PMID: 35341307 DOI: 10.1098/rsta.2020.0376] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 06/28/2021] [Indexed: 06/14/2023]
Abstract
Non-adiabatic couplings between Born-Oppenheimer (BO)-derived potential energy surfaces are now recognized as pivotal in describing the non-radiative decay of electronically excited molecules following photon absorption. This opinion piece illustrates how non-BO effects provide photostability to many biomolecules when exposed to ultraviolet radiation, yet in many other cases are key to facilitating 'reactive' outcomes like isomerization and bond fission. The examples are presented in order of decreasing molecular complexity, spanning studies of organic sunscreen molecules in solution, through two families of heteroatom containing aromatic molecules and culminating with studies of isolated gas phase H2O molecules that afford some of the most detailed insights yet available into the cascade of non-adiabatic couplings that enable the evolution from photoexcited molecule to eventual products. This article is part of the theme issue 'Chemistry without the Born-Oppenheimer approximation'.
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Affiliation(s)
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
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4
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Shenje L, Qu Y, Popik V, Ullrich S. Femtosecond photodecarbonylation of photo-ODIBO studied by stimulated Raman spectroscopy and density functional theory. Phys Chem Chem Phys 2021; 23:25637-25648. [PMID: 34783336 DOI: 10.1039/d1cp03512f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photo-oxa-dibenzocyclooctyne (Photo-ODIBO) undergoes photodecarbonylation under UV excitation to its bright S2 state, forming a highly reactive cyclooctyne, ODIBO. Following 321 nm excitation with sub-50 fs actinic pulses, the excited state evolution and cyclopropenone bond cleavage with CO release were characterized using femtosecond stimulated Raman spectroscopy and time-dependent density functional theory Raman calculations. Analysis of the photo-ODIBO S2 CO Raman band revealed multi-exponential intensity, peak splitting and frequency-shift dynamics. This suggests a stepwise cleavage of the two C-C bonds in the cyclopropenone structure that is completed within <300 fs after excitation. Evidence of intramolecular vibrational relaxation on the S2 state, concurrent with photodecarbonylation, with dynamics matching previous electronic transient absorption spectroscopy, was also observed. This confirms an excited state, as opposed to ground state, photodecarbonylation mechanism resulting in a vibronically excited photoproduct, ODIBO.
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Affiliation(s)
- Learnmore Shenje
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, USA.
| | - Yingqi Qu
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, USA.
| | - Vladimir Popik
- Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA
| | - Susanne Ullrich
- Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, USA.
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5
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Xie BB, Liu BL, Tang XF, Tang D, Shen L, Fang WH. Nonadiabatic dynamics simulation of photoinduced ring-opening reaction of 2(5 H)-thiophenone with internal conversion and intersystem crossing. Phys Chem Chem Phys 2021; 23:9867-9877. [PMID: 33908501 DOI: 10.1039/d1cp00281c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In the present work, the quantum trajectory mean-field approach, which is able to overcome the overcoherence problem, was generalized to simulate internal conversion and intersystem crossing processes simultaneously. The photoinduced ring-opening and subsequent rearrangement reactions of isolated 2(5H)-thiophenone were studied based on geometry optimizations on critical structures and nonadiabatic dynamics simulations using this method. Upon 267 nm irradiation, the molecule is initially populated in the 1ππ* state. After a sudden rupture of one C-S bond within 100 fs in this state, the lowest two singlet excited states and the lowest two triplet excited states become quasi-degenerated, and then the intersystem crossing processes between singlet and triplet states accompanied by rearrangement reactions can be observed several times. Compared with our previous nonadiabatic simulations in the absence of intersystem crossing (ChemPhotoChem, 2019, 3, 897-906), some new nonadiabatic relaxation pathways involving triplet states and different ring-opening products were identified. The present work provides new mechanistic insights into the photoinduced ring-opening of thio-substituted heterocyclic molecules and reveals the importance of nonadiabatic dynamics simulation that is able to deal with multiple electronic states with different spin multiplicities.
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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.
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6
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Liu Y, Rozgonyi T, Marquetand P, Weinacht T. Excited-state dynamics of CH 2I 2 and CH 2IBr studied with UV-pump VUV-probe momentum-resolved photoion spectroscopy. J Chem Phys 2020; 153:184304. [PMID: 33187419 DOI: 10.1063/5.0026177] [Citation(s) in RCA: 4] [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 perform time-resolved ionization spectroscopy measurements of the excited state dynamics of CH2I2 and CH2IBr following photoexcitation in the deep UV. The fragment ions produced by ionization with a vacuum-ultraviolet probe pulse are measured with velocity map imaging, and the momentum resolved yields are compared with trajectory surface hopping calculations of the measurement observable. Together with recent time-resolved photoelectron spectroscopy measurements of the same dynamics, these results provide a detailed picture of the coupled electronic and nuclear dynamics involved. Our measurements highlight the non-adiabatic coupling between electronic states, which leads to notable differences in the dissociation dynamics for the two molecules.
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Affiliation(s)
- Yusong Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Tamás Rozgonyi
- Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest, Hungary
| | - Philipp Marquetand
- University of Vienna, Faculty of Chemistry, Institute of Theoretical Chemistry, Währinger Straße 17, 1090 Wien, Austria
| | - Thomas Weinacht
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
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7
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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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Affiliation(s)
- Abigail L Whittock
- Analytical Science Centre for Doctoral Training, Senate House, University of Warwick, Coventry, United Kingdom.,Department of Chemistry, University of Warwick, Coventry, United Kingdom
| | - Matthew A P Turner
- Department of Chemistry, University of Warwick, Coventry, United Kingdom.,Molecular Analytical Science Centre for Doctoral Training, Senate House, University of Warwick, Coventry, United Kingdom.,Department of Physics, University of Warwick, Coventry, United Kingdom
| | - Daniel J L Coxon
- Department of Chemistry, University of Warwick, Coventry, United Kingdom.,Department of Physics, University of Warwick, Coventry, United Kingdom.,Diamond Science and Technology Centre for Doctoral Training, University of Warwick, Coventry, United Kingdom
| | - Jack M Woolley
- Department of Chemistry, University of Warwick, Coventry, United Kingdom
| | - Michael D Horbury
- School of Electronic and Electrical Engineering, University of Leeds, Leeds, United Kingdom
| | - Vasilios G Stavros
- Department of Chemistry, University of Warwick, Coventry, United Kingdom
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8
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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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Affiliation(s)
- Temitope T. Abiola
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK; (T.T.A.); (A.L.W.)
| | - Abigail L. Whittock
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK; (T.T.A.); (A.L.W.)
- AS CDT, Senate House, University of Warwick, Coventry CV4 7AL, UK
| | - Vasilios G. Stavros
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK; (T.T.A.); (A.L.W.)
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9
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Graziano G. Casting light on fast motion. Nat Rev Chem 2020; 4:439. [PMID: 37127966 DOI: 10.1038/s41570-020-0216-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Tracking the ultraviolet-induced photochemistry of thiophenone during and after ultrafast ring opening. Nat Chem 2020; 12:795-800. [PMID: 32690894 DOI: 10.1038/s41557-020-0507-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Accepted: 06/11/2020] [Indexed: 11/08/2022]
Abstract
Photoinduced isomerization reactions lie at the heart of many chemical processes in nature. The mechanisms of such reactions are determined by a delicate interplay of coupled electronic and nuclear dynamics occurring on the femtosecond scale, followed by the slower redistribution of energy into different vibrational degrees of freedom. Here we apply time-resolved photoelectron spectroscopy with a seeded extreme ultraviolet free-electron laser to trace the ultrafast ring opening of gas-phase thiophenone molecules following ultraviolet photoexcitation. When combined with ab initio electronic structure and molecular dynamics calculations of the excited- and ground-state molecules, the results provide insights into both the electronic and nuclear dynamics of this fundamental class of reactions. The initial ring opening and non-adiabatic coupling to the electronic ground state are shown to be driven by ballistic S-C bond extension and to be complete within 350 fs. Theory and experiment also enable visualization of the rich ground-state dynamics that involve the formation of, and interconversion between, ring-opened isomers and the cyclic structure, as well as fragmentation over much longer timescales.
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11
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Schalk O, Galiana J, Geng T, Larsson TL, Thomas RD, Fdez. Galván I, Hansson T, Vacher M. Competition between ring-puckering and ring-opening excited state reactions exemplified on 5H-furan-2-one and derivatives. J Chem Phys 2020; 152:064301. [DOI: 10.1063/1.5129366] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Oliver Schalk
- Department of Physics, AlbaNova University Center, Stockholm University, 106 91 Stockholm, Sweden
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Joachim Galiana
- Department of Chemistry–Ångström Laboratory, Uppsala University, P.O. Box 538, SE-751 21 Uppsala, Sweden
- Department of Chemistry, École normale supérieure de Lyon, 69342 Lyon, France
| | - Ting Geng
- Department of Physics, AlbaNova University Center, Stockholm University, 106 91 Stockholm, Sweden
| | - Tobias L. Larsson
- Department of Chemistry–Ångström Laboratory, Uppsala University, P.O. Box 538, SE-751 21 Uppsala, Sweden
| | - Richard D. Thomas
- Department of Physics, AlbaNova University Center, Stockholm University, 106 91 Stockholm, Sweden
| | - Ignacio Fdez. Galván
- Department of Chemistry–Ångström Laboratory, Uppsala University, P.O. Box 538, SE-751 21 Uppsala, Sweden
- Department of Chemistry–BMC, Uppsala University, P.O. Box 576, SE-751 23 Uppsala, Sweden
| | - Tony Hansson
- Department of Physics, AlbaNova University Center, Stockholm University, 106 91 Stockholm, Sweden
| | - Morgane Vacher
- Department of Chemistry–Ångström Laboratory, Uppsala University, P.O. Box 538, SE-751 21 Uppsala, Sweden
- Laboratoire CEISAM - UMR CNRS 6230, Université de Nantes, 44300 Nantes, France
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12
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Kao MH, Venkatraman RK, Ashfold MNR, Orr-Ewing AJ. Effects of ring-strain on the ultrafast photochemistry of cyclic ketones. Chem Sci 2020; 11:1991-2000. [PMID: 34123294 PMCID: PMC8148387 DOI: 10.1039/c9sc05208a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ring-strain in cyclic organic molecules is well-known to influence their chemical reactivity. Here, we examine the consequence of ring-strain for competing photochemical pathways that occur on picosecond timescales. The significance of Norrish Type-I photochemistry is explored for three cyclic ketones in cyclohexane solutions at ultraviolet (UV) excitation wavelengths from 255–312 nm, corresponding to an π* ← n excitation to the lowest excited singlet state (S1). Ultrafast transient absorption spectroscopy with broadband UV/visible probe laser pulses reveals processes common to cyclobutanone, cyclopentanone and cyclohexanone, occurring on timescales of ≤1 ps, 7–9 ps and >500 ps. These kinetic components are respectively assigned to prompt cleavage of an α C–C bond in the internally excited S1-state molecules prepared by UV absorption, vibrational cooling of these hot-S1 molecules to energies below the barrier to C–C bond cleavage on the S1 state potential energy surface (with commensurate reductions in the energy-dependent α-cleavage rate), and slower loss of thermalized S1-state population. The thermalized S1-state molecules may competitively decay by activated reaction over the barrier to α C–C bond fission on the S1-state potential energy surface, internal conversion to the ground (S0) electronic state, or intersystem crossing to the lowest lying triplet state (T1) and subsequent C–C bond breaking. The α C–C bond fission barrier height in the S1 state is significantly reduced by the ring-strain in cyclobutanone, affecting the relative contributions of the three decay time components which depend systematically on the excitation energy above the S1-state energy barrier. Transient infra-red absorption spectra obtained after UV excitation identify ring-opened ketene photoproducts of cyclobutanone and their timescales for formation. Ultrafast spectroscopy of ring-opening in three cyclic ketones reveals how ring-strain affects Norrish Type-I α-cleavage mechanisms.![]()
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Affiliation(s)
- Min-Hsien Kao
- School of Chemistry, University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | | | - Michael N R Ashfold
- School of Chemistry, University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close Bristol BS8 1TS UK
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13
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Shen L, Tang D, Xie B, Fang WH. Quantum Trajectory Mean-Field Method for Nonadiabatic Dynamics in Photochemistry. J Phys Chem A 2019; 123:7337-7350. [PMID: 31373814 DOI: 10.1021/acs.jpca.9b03480] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The mixed quantum-classical dynamical approaches have been widely used to study nonadiabatic phenomena in photochemistry and photobiology, in which the time evolutions of the electronic and nuclear subsystems are treated based on quantum and classical mechanics, respectively. The key issue is how to deal with coherence and decoherence during the propagation of the two subsystems, which has been the subject of numerous investigations for a few decades. A brief description on Ehrenfest mean-field and surface-hopping (SH) methods is first provided, and then different algorithms for treatment of quantum decoherence are reviewed in the present paper. More attentions were paid to quantum trajectory mean-field (QTMF) method under the picture of quantum measurements, which is able to overcome the overcoherence problem. Furthermore, the combined QTMF and SH algorithm is proposed in the present work, which takes advantages of the QTMF and SH methods. The potential to extend the applicability of the QTMF method was briefly discussed, such as the generalization to other type of nonadiabatic transitions, the combination with multiscale computational models, and possible improvements on its accuracy and efficiency by using machine-learning techniques.
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Affiliation(s)
- Lin Shen
- Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , P. R. China
| | - Diandong Tang
- Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , P. R. China
| | - Binbin Xie
- Hangzhou Institute of Advanced Studies , Zhejiang Normal University , 1108 Gengwen Road , Hangzhou 311231 , Zhejiang P. R. China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry of Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , P. R. China
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14
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Xie B, Fang W. Combined Quantum Trajectory Mean‐Field and Molecular Mechanical (QTMF/MM) Nonadiabatic Dynamics Simulations on the Photoinduced Ring‐Opening Reaction of 2(5H)‐Thiophenone. CHEMPHOTOCHEM 2019. [DOI: 10.1002/cptc.201900076] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Bin‐Bin Xie
- Hangzhou Institute of Advanced StudiesZhejiang Normal University 1108 Gengwen Road Hangzhou 311231, Zhejiang P. R. China
| | - Wei‐Hai Fang
- Hangzhou Institute of Advanced StudiesZhejiang Normal University 1108 Gengwen Road Hangzhou 311231, Zhejiang P. R. China
- Key Laboratory of Theoretical and Computational Photochemistry Ministry of Education College of ChemistryBeijing Normal University Beijing 100875 P. R. China
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15
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Ingle RA, Roberts GM, Röttger K, Marroux HJ, Sönnichsen FD, Yang M, Szyc Ł, Harabuchi Y, Maeda S, Temps F, Orr-Ewing AJ. Resolving the excited state relaxation dynamics of guanosine monomers and hydrogen-bonded homodimers in chloroform solution. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.07.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Dias N, Joalland B, Ariyasingha NM, Suits AG, Broderick BM. Direct versus Indirect Photodissociation of Isoxazole from Product Branching: A Chirped-Pulse Fourier Transform mm-Wave Spectroscopy/Pulsed Uniform Flow Investigation. J Phys Chem A 2018; 122:7523-7531. [PMID: 30165738 DOI: 10.1021/acs.jpca.8b04713] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The UV photodissociation of isoxazole (c-C3H3NO) is studied in this work by chirped-pulse Fourier transform mm-wave spectroscopy in a pulsed uniform Laval flow. This approach offers a number of advantages over traditional spectroscopic detection methods due to its broadband, sub-MHz resolution, and fast-acquisition capabilities. In coupling this technique with a quasi-uniform Laval flow, we are able to obtain product branching fractions in the 193 nm photodissociation of isoxazole. Five dissociation channels are explored through direct detection of seven different photoproducts. These species and their respective branching fractions (%) include the following: HCN (53.8 ± 1.7), CH3CN (23.4 ± 6.8), HCO (9.5 ± 2.3), CH2CN (7.8 ± 2.9), CH2CO (3.8 ± 0.9), HCCCN (0.9 ± 0.2), and HNC (0.8 ± 0.2). Guided by previous electronic structure and dynamics simulations, we are able to elucidate the dissociation dynamics that govern the final product branching fractions observed in this work, which differ significantly from previous reports on the thermal decomposition of isoxazole. Interestingly, both direct and indirect dynamics contribute to its dissociation, and clear signatures of both are manifested in the relative branching ratios obtained. Consistent with previous studies on the unimolecular dissociation of isoxazole, our findings also suggest the importance of the open-shell singlet diradicaloid species vinylnitrene in the dissociation dynamics, regardless of the initially populated excited state. This work, taken together with previous investigations, provides a global picture of the complex dissociation pathways involved in the photodissociation of isoxazole.
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Affiliation(s)
- Nureshan Dias
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Baptiste Joalland
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Nuwandi M Ariyasingha
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Arthur G Suits
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
| | - Bernadette M Broderick
- Department of Chemistry, University of Missouri , Columbia , Missouri 65211 , United States
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17
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Bhattacherjee A, Schnorr K, Oesterling S, Yang Z, Xue T, de Vivie-Riedle R, Leone SR. Photoinduced Heterocyclic Ring Opening of Furfural: Distinct Open-Chain Product Identification by Ultrafast X-ray Transient Absorption Spectroscopy. J Am Chem Soc 2018; 140:12538-12544. [DOI: 10.1021/jacs.8b07155] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Aditi Bhattacherjee
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Kirsten Schnorr
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Sven Oesterling
- Department of Chemistry, Ludwig-Maximilians-Universität München, München 81377, Germany
| | - Zheyue Yang
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Tian Xue
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | | | - Stephen R. Leone
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Physics, University of California, Berkeley, California 94720, United States
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18
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Röttger K, Marroux HJB, Böhnke H, Morris DTJ, Voice AT, Temps F, Roberts GM, Orr-Ewing AJ. Probing the excited state relaxation dynamics of pyrimidine nucleosides in chloroform solution. Faraday Discuss 2018; 194:683-708. [PMID: 27711889 DOI: 10.1039/c6fd00068a] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Ultrafast transient electronic and vibrational absorption spectroscopy (TEAS and TVAS) of 2'-deoxy-cytidine (dC) and 2'-deoxy-thymidine (dT) dissolved in chloroform examines their excited-state dynamics and the recovery of ground electronic state molecules following absorption of ultraviolet light. The chloroform serves as a weakly interacting solvent, allowing comparisons to be drawn with prior experimental studies of the photodynamics of these nucleosides in the gas phase and in polar solvents such as water. The pyrimidine base nucleosides have some propensity to dimerize in aprotic solvents, but the monomer photochemistry can be resolved clearly and is the focus of this study. UV absorption at a wavelength of 260 nm excites a 1ππ* ← S0 transition, but prompt crossing of a significant fraction (50% in dC, 17% in dT) of the 1ππ* population into a nearby 1nπ* state is too fast for the experiments to resolve. The remaining flux on the 1ππ* state leaves the vertical Franck-Condon region and encounters a conical intersection with the ground electronic state of ethylenic twist character. In dC, the 1ππ* state decays to the ground state with a time constant of 1.1 ± 0.1 ps. The lifetime of the 1nπ* state is much longer in the canonical forms of both molecules: recovery of the ground state population from these states occurs with time constants of 18.6 ± 1.1 ps in amino-oxo dC and ∼114 ps in dT, indicating potential energy barriers to the 1nπ*/S0 conical intersections. The small fraction of the imino-oxo tautomer of dC present in solution has a longer-lived 1nπ* state with a lifetime for ground state recovery of 193 ± 55 ps. No evidence is found for photo-induced tautomerization of amino-oxo dC to the imino-oxo form, or for population of low lying triplet states of this nucleoside. In contrast, ∼8% of the UV-excited dT molecules access the long-lived T1 (3ππ*) state through the 1nπ* state. The primary influence of the solvent appears to be the degree to which it destabilizes the states of 1nπ* character, with consequences for the lifetimes of these states as well as the triplet state yields.
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Affiliation(s)
- Katharina Röttger
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK. and Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - Hugo J B Marroux
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Hendrik Böhnke
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - David T J Morris
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Angus T Voice
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Friedrich Temps
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
| | - Gareth M Roberts
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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19
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Ma X, Wenzel M, Schmitt HC, Flock M, Reusch E, Mitrić R, Fischer I, Brixner T. Disentangling the photochemistry of benzocyclobutenedione. Phys Chem Chem Phys 2018; 20:15434-15444. [PMID: 29799041 DOI: 10.1039/c8cp01937a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ultrafast photophysics and photochemistry of benzocyclobutenedione (BCBD) dissolved in dichloromethane is investigated by transient absorption spectroscopy in both the IR and the UV/Vis regime. The molecule is excited at 300 nm to the S3 (ππ*) state and a time scale from roughly 100 fs to several nanoseconds is covered. The initially excited S3 deactivates quickly to the lower-lying S1 (nπ*) state. Three parallel photochemical reaction pathways starting in the S1 state that compete with deactivation to S0 are identified in the transient IR spectra, two of them consisting of a sequence of steps. DFT/TDDFT calculations of the normal modes of the reactant and various photoproducts support the analysis of the transient spectra. The rapid internal conversion (IC) to the S1 state of BCBD is followed by a sub-picosecond vibrational relaxation (VR) to S1 (ν = 0). In parallel BCBD loses one carbonyl group and forms benzocyclopropenone, which subsequently rearranges to cyclopentadienylidene ketene. Ring opening in the S1 (ν = 0) state produces vibrationally hot bisketene, which cools within 22 ps. This reaction competes with the intramolecular rearrangement to singlet oxacarbene, which subsequently converts into the triplet carbene via intersystem crossing (ISC). The late-time product identified in the transient UV/Vis spectra is probably due to dimerization of the carbene. Molecular dynamics (MD) simulations of the early-time photochemistry of BCBD successfully reproduce the formation of the three main photoproducts.
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Affiliation(s)
- Xiaonan Ma
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
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20
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Karsili TNV, Marchetti B, Matsika S. Origins of Photodamage in Pheomelanin Constituents: Photochemistry of 4-Hydroxybenzothiazole. J Phys Chem A 2018; 122:1986-1993. [DOI: 10.1021/acs.jpca.7b09690] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tolga N. V. Karsili
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Barbara Marchetti
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Spiridoula Matsika
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
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21
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Abstract
We have investigated the photodynamics of β-d-glucose employing our field-induced surface-hopping (FISH) method, which allows us to simulate the coupled electron-nuclear dynamics, explicitly including nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S1 and S2 states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs), whose geometries in most cases involve the elongation of a single O-H bond, whereas in some instances, ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations, explicitly including a UV laser pulse of 6.43 eV photon energy, reveal that after initial excitation, the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S1 state through the same types of CIs as observed in the field-free simulations.
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Affiliation(s)
- Jens Petersen
- Institut für physikalische und theoretische Chemie, Julius-Maximilians-Universität Würzburg , Emil-Fischer-Str. 42, 97074 Würzburg, Germany
| | - Joachim O Lindner
- Institut für physikalische und theoretische Chemie, Julius-Maximilians-Universität Würzburg , Emil-Fischer-Str. 42, 97074 Würzburg, Germany
| | - Roland Mitrić
- Institut für physikalische und theoretische Chemie, Julius-Maximilians-Universität Würzburg , Emil-Fischer-Str. 42, 97074 Würzburg, Germany
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22
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Ashfold MNR, Bain M, Hansen CS, Ingle RA, Karsili TNV, Marchetti B, Murdock D. Exploring the Dynamics of the Photoinduced Ring-Opening of Heterocyclic Molecules. J Phys Chem Lett 2017; 8:3440-3451. [PMID: 28661140 DOI: 10.1021/acs.jpclett.7b01219] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Excited states formed by electron promotion to an antibonding σ* orbital are now recognized as key to understanding the photofragmentation dynamics of a broad range of heteroatom containing small molecules: alcohols, thiols, amines, and many of their aromatic analogues. Such excited states may be populated by direct photoexcitation, or indirectly by nonadiabatic transfer of population from some other optically excited state (e.g., a ππ* state). This Perspective explores the extent to which the fast-growing literature pertaining to such (n/π)σ*-state mediated bond fissions can inform and enhance our mechanistic understanding of photoinduced ring-opening in heterocyclic molecules.
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Affiliation(s)
- Michael N R Ashfold
- School of Chemistry, University of Bristol , Bristol, United Kingdom , BS8 1TS
| | - Matthew Bain
- School of Chemistry, University of Bristol , Bristol, United Kingdom , BS8 1TS
| | | | - Rebecca A Ingle
- School of Chemistry, University of Bristol , Bristol, United Kingdom , BS8 1TS
| | - Tolga N V Karsili
- School of Chemistry, University of Bristol , Bristol, United Kingdom , BS8 1TS
| | - Barbara Marchetti
- School of Chemistry, University of Bristol , Bristol, United Kingdom , BS8 1TS
| | - Daniel Murdock
- School of Chemistry, University of Bristol , Bristol, United Kingdom , BS8 1TS
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23
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Ingle RA, Hansen CS, Elsdon E, Bain M, King SJ, Lee JWL, Brouard M, Vallance C, Turchetta R, Ashfold MNR. Ultraviolet photochemistry of 2-bromothiophene explored using universal ionization detection and multi-mass velocity-map imaging with a PImMS2 sensor. J Chem Phys 2017; 147:013914. [DOI: 10.1063/1.4979559] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Ashfold MN, Murdock D, Oliver TA. Molecular Photofragmentation Dynamics in the Gas and Condensed Phases. Annu Rev Phys Chem 2017; 68:63-82. [DOI: 10.1146/annurev-physchem-052516-050756] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Exciting a molecule with an ultraviolet photon often leads to bond fission, but the final outcome of the bond cleavage is typically both molecule and phase dependent. The photodissociation of an isolated gas-phase molecule can be viewed as a closed system: Energy and momentum are conserved, and the fragmentation is irreversible. The same is not true in a solution-phase photodissociation process. Solvent interactions may dissipate some of the photoexcitation energy prior to bond fission and will dissipate any excess energy partitioned into the dissociation products. Products that have no analog in the corresponding gas-phase study may arise by, for example, geminate recombination. Here, we illustrate the extent to which dynamical insights from gas-phase studies can inform our understanding of the corresponding solution-phase photochemistry and how, in the specific case of photoinduced ring-opening reactions, solution-phase studies can in some cases reveal dynamical insights more clearly than the corresponding gas-phase study.
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Affiliation(s)
| | - Daniel Murdock
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Thomas A.A. Oliver
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
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25
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Röttger K, Marroux HJB, Chemin AFM, Elsdon E, Oliver TAA, Street STG, Henderson AS, Galan MC, Orr-Ewing AJ, Roberts GM. Is UV-Induced Electron-Driven Proton Transfer Active in a Chemically Modified A·T DNA Base Pair? J Phys Chem B 2017; 121:4448-4455. [PMID: 28394602 DOI: 10.1021/acs.jpcb.7b02679] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Transient electronic and vibrational absorption spectroscopies have been used to investigate whether UV-induced electron-driven proton transfer (EDPT) mechanisms are active in a chemically modified adenine-thymine (A·T) DNA base pair. To enhance the fraction of biologically relevant Watson-Crick (WC) hydrogen-bonding motifs and eliminate undesired Hoogsteen structures, a chemically modified derivative of A was synthesized, 8-(tert-butyl)-9-ethyladenine (8tBA). Equimolar solutions of 8tBA and silyl-protected T nucleosides in chloroform yield a mixture of WC pairs, reverse WC pairs, and residual monomers. Unlike previous transient absorption studies of WC guanine-cytosine (G·C) pairs, no clear spectroscopic or kinetic evidence was identified for the participation of EDPT in the excited-state relaxation dynamics of 8tBA·T pairs, although ultrafast (sub-100 fs) EDPT cannot be discounted. Monomer-like dynamics are proposed to dominate in 8tBA·T.
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Affiliation(s)
- Katharina Röttger
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Hugo J B Marroux
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Arsène F M Chemin
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Emma Elsdon
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Thomas A A Oliver
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Steven T G Street
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | | | - M Carmen Galan
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Gareth M Roberts
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
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26
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Murdock D, Clark IP, Ashfold MNR. Probing Photochemically and Thermally Induced Isomerization Reactions in α-Pyrone. J Phys Chem A 2016; 120:7249-54. [DOI: 10.1021/acs.jpca.6b06396] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel Murdock
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, United Kingdom
| | - Ian P. Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technologies Facilities Council, Rutherford Appleton
Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Michael N. R. Ashfold
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, United Kingdom
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27
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Murdock D, Ingle RA, Sazanovich IV, Clark IP, Harabuchi Y, Taketsugu T, Maeda S, Orr-Ewing AJ, Ashfold MNR. Contrasting ring-opening propensities in UV-excited α-pyrone and coumarin. Phys Chem Chem Phys 2016; 18:2629-38. [PMID: 26701669 DOI: 10.1039/c5cp06597f] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photoisomerisation dynamics following excitation to the S1 electronic state of two structurally related heterocyclic molecules, α-pyrone and coumarin, in acetonitrile solution have been probed by time-resolved vibrational absorption spectroscopy. Following irradiation at 310 nm, α-pyrone relaxes rapidly from its initially excited state, with a quantum yield for parent molecule reformation of 68%. Probing the antisymmetric ketene stretch region between 2100 cm(-1) and 2150 cm(-1) confirms the presence of at least two isomeric ring-opened photoproducts, which are formed highly vibrationally excited and relax on a picosecond timescale. Following vibrational cooling, a secondary, thermally driven, isomerisation is observed with a 1.8(1) ns time constant. In contrast, coumarin reforms the parent molecule with essentially 100% efficiency following excitation at 330 nm. The conical intersections driving the non-radiative relaxation of α-pyrone have been investigated using an automated search algorithm. The two lowest energy conical intersections possess remarkably similar structures to the two energetically accessible conical intersections reported previously for coumarin, suggesting that the differing photochemistry is the result of dynamical effects occurring after passage through these intersections.
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Affiliation(s)
- Daniel Murdock
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Rebecca A Ingle
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Igor V Sazanovich
- Central Laser Facility, Research Complex at Harwell, Science and Technologies Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technologies Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
| | - Yu Harabuchi
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Tetsuya Taketsugu
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Satoshi Maeda
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
| | - Michael N R Ashfold
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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28
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Pandit S, Preston TJ, King SJ, Vallance C, Orr-Ewing AJ. Evidence for concerted ring opening and C–Br bond breaking in UV-excited bromocyclopropane. J Chem Phys 2016; 144:244312. [DOI: 10.1063/1.4954373] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Shubhrangshu Pandit
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Thomas J. Preston
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Simon J. King
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Claire Vallance
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Andrew J. Orr-Ewing
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
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29
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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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Affiliation(s)
- Rebecca A Ingle
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK BS8 1TS.
| | - Tolga N V Karsili
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK BS8 1TS.
| | - Gregg J Dennis
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK BS8 1TS.
| | - Michael Staniforth
- Department of Chemistry, University of Warwick, Library Road, Coventry, UK CV4 7AL
| | - Vasilios G Stavros
- Department of Chemistry, University of Warwick, Library Road, Coventry, UK CV4 7AL
| | - Michael N R Ashfold
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK BS8 1TS.
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30
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Carpenter BK, Harvey JN, Orr-Ewing AJ. The Study of Reactive Intermediates in Condensed Phases. J Am Chem Soc 2016; 138:4695-705. [DOI: 10.1021/jacs.6b01761] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Barry K. Carpenter
- School
of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, U.K
| | - Jeremy N. Harvey
- Department
of Chemistry, KU Leuven, Celestijnen Laan 200F, B-3001 Heverlee, Belgium
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
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Röttger K, Marroux HJB, Grubb MP, Coulter PM, Böhnke H, Henderson AS, Galan MC, Temps F, Orr‐Ewing AJ, Roberts GM. Ultraviolet Absorption Induces Hydrogen‐Atom Transfer in G⋅C Watson–Crick DNA Base Pairs in Solution. Angew Chem Int Ed Engl 2015; 54:14719-22. [DOI: 10.1002/anie.201506940] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 09/07/2015] [Indexed: 02/05/2023]
Affiliation(s)
- Katharina Röttger
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
- Institut für Physikalische Chemie, Christian‐Albrechts‐Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany)
| | - Hugo J. B. Marroux
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Michael P. Grubb
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Philip M. Coulter
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Hendrik Böhnke
- Institut für Physikalische Chemie, Christian‐Albrechts‐Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany)
| | | | - M. Carmen Galan
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Friedrich Temps
- Institut für Physikalische Chemie, Christian‐Albrechts‐Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany)
| | - Andrew J. Orr‐Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Gareth M. Roberts
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
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Röttger K, Marroux HJB, Grubb MP, Coulter PM, Böhnke H, Henderson AS, Galan MC, Temps F, Orr‐Ewing AJ, Roberts GM. Ultraviolet Absorption Induces Hydrogen‐Atom Transfer in G⋅C Watson–Crick DNA Base Pairs in Solution. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201506940] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Katharina Röttger
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
- Institut für Physikalische Chemie, Christian‐Albrechts‐Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany)
| | - Hugo J. B. Marroux
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Michael P. Grubb
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Philip M. Coulter
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Hendrik Böhnke
- Institut für Physikalische Chemie, Christian‐Albrechts‐Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany)
| | | | - M. Carmen Galan
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Friedrich Temps
- Institut für Physikalische Chemie, Christian‐Albrechts‐Universität zu Kiel, Olshausenstrasse 40, 24098 Kiel (Germany)
| | - Andrew J. Orr‐Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
| | - Gareth M. Roberts
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK)
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Würmel J, Simmie JM, Losty MM, McKenna CD. Thermal Decomposition of 2(3H) and 2(5H) Furanones: Theoretical Aspects. J Phys Chem A 2015; 119:6919-27. [PMID: 26053126 DOI: 10.1021/acs.jpca.5b04435] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermal decomposition reactions of 2(3H) and 2(5H) furanones and their methyl derivatives are explored. Theoretical calculations of the barriers, reaction enthalpies, and the properties of these and intermediate species are reported using the composite model chemistry CBS-QB3 and also the functional M06-2X allied to the 6-311++G(d,p) basis set. Thus, the bond dissociation enthalpies, ionization energies, and unimolecular chemical kinetic rate constants in the high-pressure limit were computed. We show that flow reactor experiments that intimated that heating the 2(3H) furanone converts it to the isomeric 2(5H) furanone occurs via a 1 → 2 H-transfer reaction to an open ring ketenoic aldehyde. The latter can then ring close to the other isomeric structure. The final products acrolein and carbon monoxide are only formed from 2(3H), and acrolein will further decompose to ethylene and CO. Comparable channels explain the interconversion of 5-methyl-2(3H) furanone to its 2(5H) isomer and to the formation of methyl vinyl ketone and CO. The influence of the methyl group at other positions on the ring is hardly of significance except in the case of 5-methyl-2(5H) furanone where a hydrogen atom transfer from the methyl group leads to the formation of a doubly unsaturated carboxylic compound, 2,4-pentadienoic acid. Studies of the UV photolysis of the parent compounds in both low-temperature inert argon matrices and in solution are broadly in accord with the thermal findings insofar as product formation is concerned and with our theoretical calculations. The dominant features of the early decomposition chemistry of these compounds are simple hydrogen transfer and simultaneous ring opening reactions, which do however result in some quite unusual species.
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Marchetti B, Karsili TNV, Kelly O, Kapetanopoulos P, Ashfold MNR. Near ultraviolet photochemistry of 2-bromo- and 2-iodothiophene: Revealing photoinduced ring opening in the gas phase? J Chem Phys 2015; 142:224303. [DOI: 10.1063/1.4921315] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Barbara Marchetti
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Tolga N. V. Karsili
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Orla Kelly
- Photek Ltd., 26 Castleham Road, St. Leonards-on-Sea, East Sussex TN38 9NS, United Kingdom
| | - Panos Kapetanopoulos
- Photek Ltd., 26 Castleham Road, St. Leonards-on-Sea, East Sussex TN38 9NS, United Kingdom
| | - Michael N. R. Ashfold
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
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Murdock D, Harris SJ, Clark IP, Greetham GM, Towrie M, Orr-Ewing AJ, Ashfold MNR. UV-induced isomerization dynamics of N-methyl-2-pyridone in solution. J Phys Chem A 2014; 119:88-94. [PMID: 25469643 DOI: 10.1021/jp511818k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The photoisomerization dynamics of N-methyl-2-pyridone (NMP) dissolved in CH3CN have been interrogated by time-resolved electronic and vibrational absorption spectroscopy. Irradiation at two different wavelengths (330 or 267 nm) prepares NMP(S1) molecules with very different levels of vibrational excitation, which rapidly relax to low vibrational levels of the S1 state. Internal conversion with an associated time constant of 110(4) ps, leading to reformation of NMP(S0) molecules, is identified as the dominant (>90%) decay pathway. Much of the remaining fraction undergoes a photoinitiated rearrangement to yield two ketenes (revealed by their characteristic antisymmetric C═C═O stretching modes at 2110 and 2120 cm(-1)), which are in equilibrium. The rate of ketene formation is found to be pump-wavelength dependent, consistent with ab initio electronic structure calculations which predict a barrier on the S1 potential energy surface en route to a prefulvenic conical intersection, by which isomerization is deduced to occur. Two kinetic models-differentiated by whether product branching occurs in the S1 or S0 electronic states-are presented and used with equal success in the analysis of the experimental data, highlighting the difficulties associated with deducing unambiguous mechanistic information from kinetic data alone.
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Affiliation(s)
- Daniel Murdock
- School of Chemistry, University of Bristol , Cantock's Close, Bristol, BS8 1TS, United Kingdom
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Roberts GM, Marroux HJB, Grubb MP, Ashfold MNR, Orr-Ewing AJ. On the Participation of Photoinduced N–H Bond Fission in Aqueous Adenine at 266 and 220 nm: A Combined Ultrafast Transient Electronic and Vibrational Absorption Spectroscopy Study. J Phys Chem A 2014; 118:11211-25. [DOI: 10.1021/jp508501w] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gareth M. Roberts
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Hugo J. B. Marroux
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Michael P. Grubb
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Michael N. R. Ashfold
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
| | - Andrew J. Orr-Ewing
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, United Kingdom
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