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Barbosa WG, Santos-Jr CV, Andrade RB, Lucena JR, Moura RT. Bond analysis in meta- and para-substituted thiophenols: overlap descriptors, local mode analysis, and QTAIM. J Mol Model 2024; 30:139. [PMID: 38639900 DOI: 10.1007/s00894-024-05932-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 04/07/2024] [Indexed: 04/20/2024]
Abstract
CONTEXT This study delves into the chemical nuances of thiophenols and their derivatives through a comprehensive computational analysis, moving beyond traditional energetic perspectives such as bond dissociation enthalpy and S-H dissociation dynamics. By employing the overlap model along with its topological descriptors (OP/TOP), quantum theory of atoms in molecules (QTAIM), and local vibrational mode (LVM) theories, the research provides a deeper understanding of the S-H and C-S bonding scenarios in substituted thiophenols. The investigation follows the electron-donating capacity of S-H substituent variation with the nature and positioning of other ring substituents. Energy profile analyses indicate distinct stability differences in the cis and trans conformations of meta- and para-PhSH systems, influenced by the electron-donating strength of these substituents. The study also uncovers significant variations in S-H bond distances and descriptor values, particularly in para-substituted PhSH, reflecting the influence of electron-donating or withdrawing substituents. In contrast, alterations at the meta-position show minimal effects on C-S bond descriptors, while para-substitutions markedly influence C-S bond characteristics, demonstrating a clear correlation with the electron-donating or withdrawing capabilities of the substituents. This research sheds light on the intricate bond dynamics in aromatic systems with diverse substituents, highlighting the complex interaction between electronic effects and molecular conformation. METHODS The study employs the ω B97X-D/Def2TZVP level of theory for molecular geometries, ensuring accurate characterization of structures as true minima via analytical harmonic frequency determination. The electronic properties of S-H and C-S bonds in variously substituted thiophenols were analyzed using OP/TOP, QTAIM, and LVM methodologies. Computational processes, including conformational scans, geometry optimizations, and vibrational frequency calculations, were conducted using Gaussian 09, with ultra-fine integration grids and tight convergence criteria for the SCF procedure. Bond descriptors were computed utilizing ChemBOS, Multiwfn, and LModeA software, providing a robust and detailed examination of bond properties.
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Affiliation(s)
- Willis G Barbosa
- Department of Chemistry, State University of Paraiba, Campina Grande, 58429-500, PB, Brazil
| | - Carlos V Santos-Jr
- Department of Chemistry, Federal University of Paraiba, João Pessoa, 58051-970, PB, Brazil
| | - Railton B Andrade
- Department of Chemistry, State University of Paraiba, Campina Grande, 58429-500, PB, Brazil
| | - Juracy R Lucena
- Department of Chemistry, State University of Paraiba, Campina Grande, 58429-500, PB, Brazil
| | - Renaldo T Moura
- Department of Chemistry and Physics, Center of Agrarian Sciences, Federal University of Paraiba, Areia, 58397-000, PB, Brazil.
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, Dallas, TX, 75275, USA.
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2
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Bejoy NB, Patwari GN. Photodegradation of Flutamide and Halogen Derivatives of Nitrobenzotrifluoride: The NO Release Channel. J Phys Chem A 2023; 127:7168-7174. [PMID: 37589077 DOI: 10.1021/acs.jpca.3c03024] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
The photodegradation of the nonsteroidal antiandrogen drug flutamide has been long linked to the photoisomerization involving the nitro group. In this work, the dynamics of NO photoelimination upon photolysis at 266 nm of flutamide, nitrobenzotrifluoride, and its halogen derivatives were investigated. Similar to nitrobenzene and its derivatives, a bimodal translational energy distribution was observed for the NO photofragment indicating the presence of two distinct elimination channels resulting in slow and fast components. The trends in the slow/fast branching ratio show that halogen substitution at the para position increases the triplet state yield due to the internal heavy-atom effect leading to enhancement of the fast component. Furthermore, the topology of the triplet state potential energy surface showed that the minimum energy path favors the oxaziridine ring-type intermediate over the NO2 roaming mechanism in all five molecules investigated. The steric interaction between the NO2 group and the CF3 group, which are placed in the ortho position, lowers the barrier for the formation of the oxaziridine transition state compared to that of nitrobenzene.
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Affiliation(s)
- Namitha Brijit Bejoy
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - G Naresh Patwari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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3
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Kim J, Woo KC, Kim KK, Kang M, Kim SK. Tunneling dynamics dictated by the multidimensional conical intersection seam in the πσ*‐mediated photochemistry of heteroaromatic molecules. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Junggil Kim
- Department of Chemistry, KAIST Daejeon Republic of Korea
| | - Kyung Chul Woo
- Department of Chemistry, KAIST Daejeon Republic of Korea
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences Nanyang Technological University Singapore Singapore
| | - Kuk Ki Kim
- Department of Chemistry, KAIST Daejeon Republic of Korea
| | - Minseok Kang
- Department of Chemistry, KAIST Daejeon Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST Daejeon Republic of Korea
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5
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Lim JS, You HS, Kim SY, Kim J, Park YC, Kim SK. Vibronic structure and predissociation dynamics of 2-methoxythiophenol (S 1): The effect of intramolecular hydrogen bonding on nonadiabatic dynamics. J Chem Phys 2019; 151:244305. [PMID: 31893886 DOI: 10.1063/1.5134519] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Vibronic spectroscopy and the S-H bond predissociation dynamics of 2-methoxythiophenol (2-MTP) in the S1 (ππ*) state have been investigated for the first time. Resonant two-photon ionization and slow-electron velocity map imaging (SEVI) spectroscopies have revealed that the S1-S0 transition of 2-MTP is accompanied with the planar to the pseudoplanar structural change along the out-of-plane ring distortion and the tilt of the methoxy moiety. The S1 vibronic bands up to their internal energy of ∼1000 cm-1 are assigned from the SEVI spectra taken via various S1 vibronic intermediate states with the aid of ab initio calculations. Intriguingly, Fermi resonances have been identified for some vibronic bands. The S-H bond breakage of 2-MTP occurs via tunneling through an adiabatic barrier under the S1/S2 conical intersection seam, and it is followed by the bifurcation into either the adiabatic or nonadiabatic channel at the S0/S2 conical intersection where the diabatic S2 state (πσ*) is unbound with respect to the S-H bond elongation coordinate, giving the excited (Ã) or ground (X̃) state of the 2-methoxythiophenoxy radical, respectively. Surprisingly, the nonadiabatic transition probability at the S0/S2 conical intersection, estimated from the velocity map ion images of the nascent D fragment from 2-MTP-d1 (2-CH3O-C6H4SD) at the S1 zero-point energy level, is found to be exceptionally high to give the X̃/Ã product branching ratio of 2.03 ± 0.20, which is much higher than the value of ∼0.8 estimated for the bare thiophenol at the S1 origin. It even increases to 2.33 ± 0.17 at the ν45 2 mode (101 cm-1) before it rapidly decays to 0.69 ± 0.05 at the S1 internal energy of about 2200 cm-1. This suggests that the strong intramolecular hydrogen bonding of S⋯D⋯OCH3 in 2-MTP at least in the low S1 internal energy region should play a significant role in localizing the reactive flux onto the conical intersection seam. The minimum energy pathway calculations (second-order coupled-cluster resolution of the identity or time-dependent-density functional theory) of the adiabatic S1 state suggest that the intimate dynamic interplay between the S-H bond cleavage and intramolecular hydrogen bonding could be crucial in the nonadiabatic surface hopping dynamics taking place at the conical intersection.
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Affiliation(s)
- Jean Sun Lim
- Department of Chemistry, KAIST, Daejeon 34141, South Korea
| | - Hyun Sik You
- Department of Chemistry, KAIST, Daejeon 34141, South Korea
| | - So-Yeon Kim
- Department of Chemistry, KAIST, Daejeon 34141, South Korea
| | - Junggil Kim
- Department of Chemistry, KAIST, Daejeon 34141, South Korea
| | | | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 34141, South Korea
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6
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Zhang L, Truhlar DG, Sun S. Full-dimensional three-state potential energy surfaces and state couplings for photodissociation of thiophenol. J Chem Phys 2019; 151:154306. [DOI: 10.1063/1.5124870] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Linyao Zhang
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Shaozeng Sun
- School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
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7
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Tew DP, Hättig C, Graf NK. Anharmonic excited state frequencies of para-difluorobenzene, toluene and catechol using analytic RI-CC2 second derivatives. Phys Chem Chem Phys 2019; 21:14063-14072. [PMID: 30656295 DOI: 10.1039/c8cp06952b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Analytic second nuclear derivatives for excited electronic state energies have been implemented for the resolution-of-the-identity accelerated CC2, CIS(D∞) and ADC(2) models. Our efficient implementation with O(N2) memory demands enables the treatment of medium sized molecules with large basis sets and high numerical precision and thereby paves the way for semi-numerical evaluation of the higher-order derivatives required for anharmonic corrections to excited state vibrational frequencies. We compare CC2 harmonic and anharmonic excited state frequencies with experimental values for para-difluorobenzene, toluene and catechol. Basis set problems occur for out-of-plane bending vibrations due to intramolecular basis set superposition error. For non-planar molecules and in plane modes of planar molecules, the agreement between theory and experiment is better than 30 cm-1 on average and we reassign a number of experimental bands on the basis of the ab initio predictions.
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Affiliation(s)
- David P Tew
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
| | - Christof Hättig
- Quantum Chemistry Group, Ruhr-Universität Bochum, 44780 Bochum, Germany.
| | - Nora K Graf
- Quantum Chemistry Group, Ruhr-Universität Bochum, 44780 Bochum, Germany.
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8
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Lim JS, You HS, Han S, Kim SK. Photodissociation Dynamics of Ortho-Substituted Thiophenols at 243 nm. J Phys Chem A 2019; 123:2634-2639. [DOI: 10.1021/acs.jpca.9b00803] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jean Sun Lim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Hyun Sik You
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Songhee Han
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
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9
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Gil ES, de Araújo BB, Gonçalves PFB. CASPT2, CASSCF and non-adiabatic molecular dynamics (NAMD) studies on the low-lying electronic states of 1 H-1,2,3-triazole photolysis. Phys Chem Chem Phys 2019; 21:25809-25819. [DOI: 10.1039/c9cp04313f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The photolysis mechanisms of 1H-1,2,3-triazole and 1H-1,2,3-benzotriazole were elucidated by employing multiconfigurational methods (CASSCF and CASPT2) and non-adiabatic molecular dynamics.
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Affiliation(s)
- Eduarda Sangiogo Gil
- Grupo de Química Teórica
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre
- Brazil
| | - Bruno Bercini de Araújo
- Grupo de Química Teórica
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre
- Brazil
| | - Paulo F. B. Gonçalves
- Grupo de Química Teórica
- Universidade Federal do Rio Grande do Sul – Instituto de Química
- Porto Alegre
- Brazil
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10
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Cooper GA, Hansen CS, Karsili TNV, Ashfold MNR. Photofragment Translational Spectroscopy Studies of H Atom Loss Following Ultraviolet Photoexcitation of Methimazole in the Gas Phase. J Phys Chem A 2018; 122:9869-9878. [DOI: 10.1021/acs.jpca.8b09859] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Graham A. Cooper
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Christopher S. Hansen
- School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Tolga N. V. Karsili
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, Louisiana 70504, United States
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11
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Ashfold MNR, Yuan K, Yang X. Perspective: The development and applications of H Rydberg atom translational spectroscopy methods. J Chem Phys 2018; 149:080901. [PMID: 30193478 DOI: 10.1063/1.5047911] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
| | - Kaijun Yuan
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
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12
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Abstract
The dynamics of chemical reactions in liquid solutions are now amenable to direct study using ultrafast laser spectroscopy techniques and advances in computer simulation methods. The surrounding solvent affects the chemical reaction dynamics in numerous ways, which include: (i) formation of complexes between reactants and solvent molecules; (ii) modifications to transition state energies and structures relative to the reactants and products; (iii) coupling between the motions of the reacting molecules and the solvent modes, and exchange of energy; (iv) solvent caging of reactants and products; and (v) structural changes to the solvation shells in response to the changing chemical identity of the solutes, on timescales which may be slower than the reactive events. This article reviews progress in the study of bimolecular chemical reaction dynamics in solution, concentrating on reactions which occur on ground electronic states. It illustrates this progress with reference to recent experimental and computational studies, and considers how the various ways in which a solvent affects the chemical reaction dynamics can be unravelled. Implications are considered for research in fields such as mechanistic synthetic chemistry.
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Affiliation(s)
- 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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Zhang L, Truhlar DG, Sun S. Electronic spectrum and characterization of diabatic potential energy surfaces for thiophenol. Phys Chem Chem Phys 2018; 20:28144-28154. [DOI: 10.1039/c8cp05215h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present an accurate simulation of the UV spectrum and a diabatization of three singlet potential surfaces along four coordinates.
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Affiliation(s)
- Linyao Zhang
- School of Energy Science and Engineering
- Harbin Institute of Technology
- Harbin 150001
- P. R. China
- Department of Chemistry
| | - Donald G. Truhlar
- Department of Chemistry
- Chemical Theory Center, and Supercomputing Institute
- University of Minnesota
- Minneapolis
- USA
| | - Shaozeng Sun
- School of Energy Science and Engineering
- Harbin Institute of Technology
- Harbin 150001
- P. R. China
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14
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Lin GSM, Xie C, Xie D. Three-Dimensional Diabatic Potential Energy Surfaces for the Photodissociation of Thiophenol. J Phys Chem A 2017; 121:8432-8439. [DOI: 10.1021/acs.jpca.7b09070] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guang-Shuang-Mu Lin
- Institute
of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic
Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
| | - Changjian Xie
- Department
of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Daiqian Xie
- Institute
of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic
Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
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15
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Kim SY, Lee J, Kim SK. Conformer specific nonadiabatic reaction dynamics in the photodissociation of partially deuterated thioanisoles (C 6H 5S-CH 2D and C 6H 5S-CHD 2). Phys Chem Chem Phys 2017; 19:18902-18912. [PMID: 28707684 DOI: 10.1039/c7cp03036c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work, we have investigated nonadiabatic dynamics in the vicinity of conical intersections for predissociation reactions of partially deuterated thioanisole molecules: C6H5S-CH2D and C6H5S-CHD2. Each isotopomer has two distinct rotational conformers according to the geometrical position of D or H of the methyl moiety with respect to the molecular plane for C6H5S-CH2D or C6H5S-CHD2, respectively, as spectroscopically characterized in our earlier report [J. Lee, S.-Y. Kim and S. K. Kim, J. Phys. Chem. A, 2014, 118, 1850]. Since identification and separation of two different rotational conformers of each isotopomer have been unambiguously done, we could interrogate nonadiabatic dynamics of thioanisole in terms of both H/D substitutional and conformational structural effects. Nonadiabatic transition probability, estimated by the experimentally measured branching ratio of the nonadiabatically produced ground-state channel giving C6H5S·(X[combining tilde]) versus the adiabatic excited-state channel leading to the C6H5S·(Ã) radical, shows resonance-like increases at symmetric (νs) or asymmetric (7a) S-CH2D (or S-CHD2) stretching mode excitation in S1 for all conformational isomers of two isotopomers. However, absolute probabilistic value of the nonadiabatic transition is found to vary quite drastically depending on different conformers and isotopomers. The experimental finding that nonadiabatic transition dynamics are very sensitive to subtle changes in the nuclear configuration within the Franck-Condon region induced by the H/D substitution indicates that the S1/S2 conical intersection seam is quite narrowly defined in the multi-dimensional nuclear configurational space as far as the S-methyl predissociation reaction is concerned. In order to understand the relation between molecular structure and nonadiabaticity of reaction, potential energy surfaces near S1/S2 conical intersections have been theoretically calculated along νs and 7a normal mode coordinates for all conformational isomers. Slow-electron velocity map imaging (SEVI) spectroscopy is employed to unravel the extent of intramolecular vibrational redistribution (IVR) for particular mode excitations of S1, providing insights into the dynamic interplay between IVR and nonadiabatic transition probability near the conical intersection seam.
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Affiliation(s)
- So-Yeon Kim
- Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea.
| | - Jeongmook Lee
- Nuclear Chemistry Research Division, Korea Atomic Energy Research Institute, Daejeon 305-353, Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea.
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16
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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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17
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Marchetti B, Karsili TNV, Cipriani M, Hansen CS, Ashfold MNR. The near ultraviolet photodissociation dynamics of 2- and 3-substituted thiophenols: Geometric vs. electronic structure effects. J Chem Phys 2017; 147:013923. [DOI: 10.1063/1.4980035] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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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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19
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Koyama D, Orr-Ewing AJ. Photochemical reaction dynamics of 2,2'-dithiobis(benzothiazole): direct observation of the addition product of an aromatic thiyl radical to an alkene with time-resolved vibrational and electronic absorption spectroscopy. Phys Chem Chem Phys 2017; 18:12115-27. [PMID: 27076054 DOI: 10.1039/c6cp01290f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photochemical reaction dynamics of the benzothiazole-2-thiyl (BS) radical, produced by 330 nm ultraviolet photolysis of 2,2'-dithiobis(benzothiazole) (BSSB), are examined on the picosecond time scale. The initial addition product of a thiol-ene reaction between the BS radical and styrene is directly observed by transient vibrational absorption spectroscopy (TVAS). Transient electronic absorption spectroscopy (TEAS) in the ultraviolet and visible spectral regions reveals rapid formation of the ground state BS radical with a time constant of ∼200 fs. The photolytically generated BS radical decays through geminate recombination to the parent molecule BSSB and competitive formation of a BS radical dimer with a rate coefficient of (3.7 ± 0.2) × 10(10) M(-1) s(-1) in methanol, and thereafter (36 ± 1)% of the initially formed BS radicals survive at the longest time delay (1.3 ns). In styrene solution, in contrast to methanol and toluene solutions, kinetic traces of the BS radical show an additional decay with a time constant of 305 ± 13 ps, and a broad band at 345-500 nm grows with the same time constant, suggesting a bimolecular reaction of the BS radical with styrene. The TVAS measurements reveal an absorption band of the ground state BS radical at 1301 cm(-1) in toluene solution, and the band decays with a time constant of 294 ± 32 ps in styrene solution. Two product bands grow at 1239 cm(-1) and 1429 cm(-1) with respective time constants of 312 ± 68 ps and 325 ± 33 ps, and are attributed to the addition product BS-St radical formed from the BS radical and styrene. A bimolecular reaction rate coefficient of kreact = (3.8 ± 0.2) × 10(8) M(-1) s(-1) is deduced and 22 ± 1% of the initially formed BS radicals are converted to the BS-St radical in neat styrene solution.
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Affiliation(s)
- Daisuke Koyama
- 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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20
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Koyama D, Donaldson PM, Orr-Ewing AJ. Femtosecond to microsecond observation of the photochemical reaction of 1,2-di(quinolin-2-yl)disulfide with methyl methacrylate. Phys Chem Chem Phys 2017; 19:12981-12991. [DOI: 10.1039/c7cp01784g] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Multiple radical reaction steps have been observed in a continuous sequence with sub-picosecond to microsecond transient absorption spectroscopy.
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Affiliation(s)
- Daisuke Koyama
- School of Chemistry
- University of Bristol
- Cantock's Close
- Bristol BS8 1TS
- UK
| | - Paul M. Donaldson
- Central Laser Facility
- Research Complex at Harwell
- Science and Technology Facilities Council
- Rutherford Appleton Laboratory
- Didcot
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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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22
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Oliver TAA, Zhang Y, Roy A, Ashfold MNR, Bradforth SE. Exploring Autoionization and Photoinduced Proton-Coupled Electron Transfer Pathways of Phenol in Aqueous Solution. J Phys Chem Lett 2015; 6:4159-4164. [PMID: 26722792 DOI: 10.1021/acs.jpclett.5b01861] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The excited state dynamics of phenol in water have been investigated using transient absorption spectroscopy. Solvated electrons and vibrationally cold phenoxyl radicals are observed upon 200 and 267 nm excitation, but with formation time scales that differ by more than 4 orders of magnitude. The impact of these findings is assessed in terms of the relative importance of autoionization versus proton-coupled electron transfer mechanisms in this computationally tractable model system.
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Affiliation(s)
- Thomas A A Oliver
- School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom
| | - Yuyuan Zhang
- University of Southern California , Los Angeles, California 90089, United States
| | - Anirban Roy
- University of Southern California , Los Angeles, California 90089, United States
| | - Michael N R Ashfold
- School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom
| | - Stephen E Bradforth
- University of Southern California , Los Angeles, California 90089, United States
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23
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You HS, Han S, Yoon JH, Lim JS, Lee J, Kim SY, Ahn DS, Lim JS, Kim SK. Structure and dynamic role of conical intersections in the πσ*-mediated photodissociation reactions. INT REV PHYS CHEM 2015. [DOI: 10.1080/0144235x.2015.1072364] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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24
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An H, Choi H, Lee YS, Baeck KK. Factors Affecting the Branching Ratio of Photodissociation: Thiophenol Studied through Quantum Wavepacket Dynamics. Chemphyschem 2015; 16:1529-34. [DOI: 10.1002/cphc.201500060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Indexed: 11/07/2022]
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25
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Wenge AM, Karsili TNV, Rodríguez JD, Cotterell MI, Marchetti B, Dixon RN, Ashfold MNR. Tuning photochemistry: substituent effects on πσ* state mediated bond fission in thioanisoles. Phys Chem Chem Phys 2015; 17:16246-56. [DOI: 10.1039/c5cp01660f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electronic branching in the thiophenoxyl radicals formed by UV photolysis of thioanisole can be tuned by placing electron withdrawing/donating substituents at the 4-position.
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Affiliation(s)
- Andreas M. Wenge
- School of Chemistry
- University of Bristol
- Cantock's Close
- Bristol BS8 1TS
- UK
| | | | | | | | - Barbara Marchetti
- School of Chemistry
- University of Bristol
- Cantock's Close
- Bristol BS8 1TS
- UK
| | - Richard N. Dixon
- School of Chemistry
- University of Bristol
- Cantock's Close
- Bristol BS8 1TS
- UK
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26
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Han S, You HS, Kim SY, Kim SK. Dynamic Role of the Intramolecular Hydrogen Bonding in Nonadiabatic Chemistry Revealed in the UV Photodissociation Reactions of 2-Fluorothiophenol and 2-Chlorothiophenol. J Phys Chem A 2014; 118:6940-9. [DOI: 10.1021/jp505699w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Songhee Han
- Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea
| | - Hyun Sik You
- Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea
| | - So-Yeon Kim
- Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea
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27
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Broderick BM, Lee Y, Doyle MB, Chernyak VY, Vasyutinskii OS, Suits AG. Spin-polarized hydrogen Rydberg time-of-flight: experimental measurement of the velocity-dependent H atom spin-polarization. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:053103. [PMID: 24880349 DOI: 10.1063/1.4871995] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We have developed a new experimental method allowing direct detection of the velocity dependent spin-polarization of hydrogen atoms produced in photodissociation. The technique, which is a variation on the H atom Rydberg time-of-flight method, employs a double-resonance excitation scheme and experimental geometry that yields the two coherent orientation parameters as a function of recoil speed for scattering perpendicular to the laser propagation direction. The approach, apparatus, and optical layout we employ are described here in detail and demonstrated in application to HBr and DBr photolysis at 213 nm. We also discuss the theoretical foundation for the approach, as well as the resolution and sensitivity we achieve.
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Affiliation(s)
| | - Yumin Lee
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Michael B Doyle
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Vladimir Y Chernyak
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Oleg S Vasyutinskii
- Ioffe Institute, Russian Academy of Sciences, St. Petersburg 194021, Russia and St. Petersburg State Polytechnic University, St. Petersburg 195251, Russia
| | - Arthur G Suits
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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28
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Capello MC, Broquier M, Ishiuchi SI, Sohn WY, Fujii M, Dedonder-Lardeux C, Jouvet C, Pino GA. Fast Nonradiative Decay in o-Aminophenol. J Phys Chem A 2014; 118:2056-62. [DOI: 10.1021/jp411457v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Marcela C. Capello
- Instituto
de Investigaciones en Físico Química de Córdoba
(INFIQC) CONICET, UNC. Dpto. de Fisicoquímica, Facultad de
Ciencias Químicas, Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina
| | - Michel Broquier
- Centre Laser de l’Université Paris Sud (CLUPS,
LUMAT FR 2764) Bât. 106, Univ
Paris-Sud 11, 91405 Orsay Cedex, France
- Institut des Sciences Moléculaires d’Orsay (ISMO,
UMR8624 CNRS) Bât. 210, Univ
Paris-Sud 11, 91405 Orsay Cedex, France
| | - Shun-Ichi Ishiuchi
- Chemical
Resources Laboratory and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku,Yokohama 226-8503, Japan
| | - Woon Y. Sohn
- Chemical
Resources Laboratory and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku,Yokohama 226-8503, Japan
| | - Masaaki Fujii
- Chemical
Resources Laboratory and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku,Yokohama 226-8503, Japan
| | - Claude Dedonder-Lardeux
- Physique
des Interactions Ioniques et Moléculaires (PIIM), UMR-CNRS 7345 Aix-Marseille Université, Avenue Escadrille Normandie-Niémen, 13397 Marseille Cedex 20, France
| | - Christophe Jouvet
- Physique
des Interactions Ioniques et Moléculaires (PIIM), UMR-CNRS 7345 Aix-Marseille Université, Avenue Escadrille Normandie-Niémen, 13397 Marseille Cedex 20, France
| | - Gustavo A. Pino
- Instituto
de Investigaciones en Físico Química de Córdoba
(INFIQC) CONICET, UNC. Dpto. de Fisicoquímica, Facultad de
Ciencias Químicas, Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina
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29
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Harrison AW, Lim JS, Ryazanov M, Wang G, Gao S, Neumark DM. Photodissociation dynamics of the thiophenoxy radical at 248, 193, and 157 nm. J Phys Chem A 2013; 117:11970-8. [PMID: 23822615 DOI: 10.1021/jp403229h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The photodissociation dynamics of the thiophenoxy radical (C6H5S) have been investigated using fast beam coincidence translational spectroscopy. Thiophenoxy radicals were produced by photodetachment of the thiophenoxide anion followed by photodissociation at 248 nm (5.0 eV), 193 nm (6.4 eV), and 157 nm (7.9 eV). Experimental results indicate two major competing dissociation channels leading to SH + C6H4 (o-benzyne) and CS + C5H5 (cyclopentadienyl) with a minor contribution of S + C6H5 (phenyl). Photofragment mass distributions and translational energy distributions were measured at each dissociation wavelength. Transition states and minima for each reaction pathway were calculated using density functional theory to facilitate experimental interpretation. The proposed dissociation mechanism involves internal conversion from the initially prepared electronic excited state to the ground electronic state followed by statistical dissociation. Calculations show that SH loss involves a single isomerization step followed by simple bond fission. For both SH and S loss, C-S bond cleavage proceeds without an exit barrier. By contrast, the CS loss pathway entails multiple transition states and minima as it undergoes five membered ring formation and presents a small barrier with respect to products. The calculated reaction pathway is consistent with the experimental translational energy distributions in which the CS loss channel has a broader distribution peaking farther away from zero than the corresponding distributions for SH loss.
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Affiliation(s)
- Aaron W Harrison
- Department of Chemistry, University of California , Berkeley, California 94720, United States
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30
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Zhang Y, Oliver TAA, Das S, Roy A, Ashfold MNR, Bradforth SE. Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol. J Phys Chem A 2013; 117:12125-37. [DOI: 10.1021/jp405160n] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuyuan Zhang
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Thomas A. A. Oliver
- School of Chemistry, Cantocks Close, University of Bristol, Bristol BS8 1TS, U.K
| | - Saptaparna Das
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Anirban Roy
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | | | - Stephen E. Bradforth
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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31
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Harris SJ, Murdock D, Zhang Y, Oliver TAA, Grubb MP, Orr-Ewing AJ, Greetham GM, Clark IP, Towrie M, Bradforth SE, Ashfold MNR. Comparing molecular photofragmentation dynamics in the gas and liquid phases. Phys Chem Chem Phys 2013; 15:6567-82. [PMID: 23552482 DOI: 10.1039/c3cp50756d] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This article explores the extent to which insights gleaned from detailed studies of molecular photodissociations in the gas phase (i.e. under isolated molecule conditions) can inform our understanding of the corresponding photofragmentation processes in solution. Systems selected for comparison include a thiophenol (p-methylthiophenol), a thioanisole (p-methylthioanisole) and phenol, in vacuum and in cyclohexane solution. UV excitation in the gas phase results in RX-Y (X = O, S; Y = H, CH3) bond fission in all cases, but over timescales that vary by ~4 orders of magnitude - all of which behaviours can be rationalised on the basis of the relevant bound and dissociative excited state potential energy surfaces (PESs) accessed by UV photoexcitation, and of the conical intersections that facilitate radiationless transfer between these PESs. Time-resolved UV pump-broadband UV/visible probe and/or UV pump-broadband IR probe studies of the corresponding systems in cyclohexane solution reveal additional processes that are unique to the condensed phase. Thus, for example, the data clearly reveal evidence of (i) vibrational relaxation of the photoexcited molecules prior to their dissociation and of the radical fragments formed upon X-Y bond fission, and (ii) geminate recombination of the RX and Y products (leading to reformation of the ground state parent and/or isomeric adducts). Nonetheless, the data also show that, in each case, the characteristics (and the timescale) of the initial bond fission process that occurs under isolated molecule conditions are barely changed by the presence of a weakly interacting solvent like cyclohexane. These condensed phase studies are then extended to an ether analogue of phenol (allyl phenyl ether), wherein UV photo-induced RO-allyl bond fission constitutes the first step of a photo-Claisen rearrangement.
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Affiliation(s)
- Stephanie J Harris
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
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32
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Karsili TNV, Wenge AM, Harris SJ, Murdock D, Harvey JN, Dixon RN, Ashfold MNR. O–H bond fission in 4-substituted phenols: S1 state predissociation viewed in a Hammett-like framework. Chem Sci 2013. [DOI: 10.1039/c3sc50296a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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33
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Roberts GM, Hadden DJ, Bergendahl LT, Wenge AM, Harris SJ, Karsili TNV, Ashfold MNR, Paterson MJ, Stavros VG. Exploring quantum phenomena and vibrational control in σ* mediated photochemistry. Chem Sci 2013. [DOI: 10.1039/c2sc21865h] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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34
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Ashfold MNR. Photoinitiated quantum molecular dynamics: Concluding Remarks. Faraday Discuss 2013; 163:545-51. [DOI: 10.1039/c3fd00090g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Murdock D, Harris SJ, Karsili TNV, Greetham GM, Clark IP, Towrie M, Orr Ewing AJ, Ashfold MNR. Photofragmentation Dynamics in Solution Probed by Transient IR Absorption Spectroscopy: πσ*-Mediated Bond Cleavage in p-Methylthiophenol and p-Methylthioanisole. J Phys Chem Lett 2012; 3:3715-3720. [PMID: 26291101 DOI: 10.1021/jz301755p] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The 267 nm photodissociation dynamics of p-methylthiophenol (p-MePhSH) and p-methylthioanisole (p-MePhSMe) dissolved in CD3CN have been probed by subpicosecond time-resolved broadband infrared spectroscopy. Prompt (τ < 1 ps) S-H bond fission in p-MePhSH is confirmed by monitoring the time-evolution of the parent (S0) bleach and the transient absorption of the p-MePhS products. Vibrational relaxation of the latter occurs on a ∼8.5 ps time scale, and ∼40% of the total radical population undergoes geminate recombination over a ∼150 ps time scale, yielding (mainly) the p-MePhSH(S0) parent. S-Me bond fission following photoexcitation to the S1 state of p-MePhSMe occurs over a much longer timescale, with a rate that is very dependent on the degree of vibrational excitation within S1. The various findings are compared and contrasted with results from complementary gas-phase photofragmentation studies of both molecules, which are shown to provide a valuable starting point for describing the solution-phase dynamics.
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Affiliation(s)
- Daniel Murdock
- †School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom
| | - Stephanie J Harris
- †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
| | - Gregory M Greetham
- ‡Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Ian P Clark
- ‡Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Michael Towrie
- ‡Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, United Kingdom
| | - Andrew J Orr Ewing
- †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
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