1
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Fidler AP, Chen L, McKillop AM, Weichman ML. Ultrafast dynamics of CN radical reactions with chloroform solvent under vibrational strong coupling. J Chem Phys 2023; 159:164302. [PMID: 37870135 DOI: 10.1063/5.0167410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 08/21/2023] [Indexed: 10/24/2023] Open
Abstract
Polariton chemistry may provide a new means to control molecular reactivity, permitting remote, reversible modification of reaction energetics, kinetics, and product yields. A considerable body of experimental and theoretical work has already demonstrated that strong coupling between a molecular vibrational mode and the confined electromagnetic field of an optical cavity can alter chemical reactivity without external illumination. However, the mechanisms underlying cavity-altered chemistry remain unclear in large part because the experimental systems examined previously are too complex for detailed analysis of their reaction dynamics. Here, we experimentally investigate photolysis-induced reactions of cyanide radicals with strongly-coupled chloroform (CHCl3) solvent molecules and examine the intracavity rates of photofragment recombination, solvent complexation, and hydrogen abstraction. We use a microfluidic optical cavity fitted with dichroic mirrors to facilitate vibrational strong coupling (VSC) of the C-H stretching mode of CHCl3 while simultaneously permitting optical access at visible wavelengths. Ultrafast transient absorption experiments performed with cavities tuned on- and off-resonance reveal that VSC of the CHCl3 C-H stretching transition does not significantly modify any measured rate constants, including those associated with the hydrogen abstraction reaction. This work represents, to the best of our knowledge, the first experimental study of an elementary bimolecular reaction under VSC. We discuss how the conspicuous absence of cavity-altered effects in this system may provide insights into the mechanisms of modified ground state reactivity under VSC and help bridge the divide between experimental results and theoretical predictions in vibrational polariton chemistry.
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Affiliation(s)
- Ashley P Fidler
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Liying Chen
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | | | - Marissa L Weichman
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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2
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Nimmrich A, Panman MR, Berntsson O, Biasin E, Niebling S, Petersson J, Hoernke M, Björling A, Gustavsson E, van Driel TB, Dohn AO, Laursen M, Zederkof DB, Tono K, Katayama T, Owada S, Nielsen MM, Davidsson J, Uhlig J, Hub JS, Haldrup K, Westenhoff S. Solvent-Dependent Structural Dynamics in the Ultrafast Photodissociation Reaction of Triiodide Observed with Time-Resolved X-ray Solution Scattering. J Am Chem Soc 2023. [PMID: 37163700 PMCID: PMC10375522 DOI: 10.1021/jacs.3c00484] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Resolving the structural dynamics of bond breaking, bond formation, and solvation is required for a deeper understanding of solution-phase chemical reactions. In this work, we investigate the photodissociation of triiodide in four solvents using femtosecond time-resolved X-ray solution scattering following 400 nm photoexcitation. Structural analysis of the scattering data resolves the solvent-dependent structural evolution during the bond cleavage, internal rearrangements, solvent-cage escape, and bond reformation in real time. The nature and structure of the reaction intermediates during the recombination are determined, elucidating the full mechanism of photodissociation and recombination on ultrafast time scales. We resolve the structure of the precursor state for recombination as a geminate pair. Further, we determine the size of the solvent cages from the refined structures of the radical pair. The observed structural dynamics present a comprehensive picture of the solvent influence on structure and dynamics of dissociation reactions.
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Affiliation(s)
- Amke Nimmrich
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Matthijs R Panman
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Oskar Berntsson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Elisa Biasin
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Stephan Niebling
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Jonas Petersson
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, 75120 Uppsala, Sweden
| | - Maria Hoernke
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Alexander Björling
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Emil Gustavsson
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
| | - Tim B van Driel
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Asmus O Dohn
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
- Faculty of Physical Sciences, University of Iceland, VR-III, 107 Reykjavík, Iceland
| | - Mads Laursen
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Diana B Zederkof
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Tetsuo Katayama
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Shigeki Owada
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Martin M Nielsen
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Jan Davidsson
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, 75120 Uppsala, Sweden
| | - Jens Uhlig
- Department of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden
| | - Jochen S Hub
- Georg-August-Universität Göttingen, Institute for Microbiology and Genetics, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Kristoffer Haldrup
- Department of Physics, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Sebastian Westenhoff
- Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden
- Department of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden
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3
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Molecular Dynamics Study of the Photodissociation of ICN in Ethanol: Effect of Solvent Polarity. J SOLUTION CHEM 2021. [DOI: 10.1007/s10953-021-01094-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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Blancafort-Jorquera M, Vilà A, González M. Rotational energy relaxation quantum dynamics of a diatomic molecule in a superfluid helium nanodroplet and study of the hydrogen isotopes case. Phys Chem Chem Phys 2019; 21:21007-21021. [PMID: 31528895 DOI: 10.1039/c9cp00952c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The rotational energy relaxation (RER) of a molecule X2(j,mj) in a 4He superfluid nanodroplet [HeND or (4He)N; T = 0.37 K] has been investigated using a hybrid quantum dynamics approach recently proposed by us. As far as we know, this is the first theoretical study about rotational relaxation inside HeNDs, and here several (real and hypothetical) isotopes of H2 have been examined, in order to analyze the influence of the rotational constant Be of these fast rotors on the dynamics. The structure of the nanodroplet practically does not change during the RER process, which approximately takes place according to a cascade mechanism j → j - 2; j - 2 → j - 4; …; 2 → 0, and mj is conserved. The results are consistent with the very scarce estimated experimental data available. The lifetime of an excited rotational state (≈1.0-7.6 ns) increases when: (a) Be increases; (b) j increases; and (c) N decreases (above N = 100 there is a small influence of N on the lifetime). This also applies to the global relaxation time and transition time. The analysis of the influence of the coupling between the j and j - 2 rotational states (due to the X2-helium interaction) and the X2 angular velocity on the lifetime and related properties has been helpful to better understand the dynamics. In contrast to the RER results, for the vibrational energy relaxation (VER) in HeNDs, when the quantum number v increases a decrease is observed in the lifetime of the excited vibrational state. This difference can be interpreted taking into account that RER and VER are associated with very different types of motion. Besides, in VER the intermediate excited states show metastability, differing from the RER case. We hope that the present study will encourage more studies to be developed on the RER dynamics in HeNDs, a basic, interesting and difficult to study physical phenomenon about which we still know very little.
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Affiliation(s)
- Miquel Blancafort-Jorquera
- Departament de Ciència de Materials i Química Física and IQTC, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain.
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5
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Athokpam B, Ramesh SG. Alkyl hydrogen atom abstraction reactions of the CN radical with ethanol. J Chem Phys 2018; 148:134503. [PMID: 29626852 DOI: 10.1063/1.5021634] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a study of the abstraction of alkyl hydrogen atoms from the β and α positions of ethanol by the CN radical in solution using the Empirical Valence Bond (EVB) method. We have built separate 2 × 2 EVB models for the Hβ and Hα reactions, where the atom transfer is parameterized using ab initio calculations. The intra- and intermolecular potentials of the reactant and product molecules were modelled with the General AMBER Force Field, with some modifications. We have carried out the dynamics in water and chloroform, which are solvents of contrasting polarity. We have computed the potential of mean force for both abstractions in each of the solvents. They are found to have a small and early barrier along the reaction coordinate with a large energy release. Analyzing the solvent structure around the reaction system, we have found two solvents to have little effect on either reaction. Simulating the dynamics from the transition state, we also study the fate of the energies in the HCN vibrational modes. The HCN molecule is born vibrationally hot in the CH stretch in both reactions and additionally in the HCN bends for the Hα abstraction reaction. In the early stage of the dynamics, we find that the CN stretch mode gains energy at the expense of the energy in CH stretch mode.
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Affiliation(s)
- Bijyalaxmi Athokpam
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
| | - Sai G Ramesh
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
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6
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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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7
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Translational, rotational and vibrational relaxation dynamics of a solute molecule in a non-interacting solvent. Nat Chem 2016; 8:1042-1046. [DOI: 10.1038/nchem.2570] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 06/10/2016] [Indexed: 11/08/2022]
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8
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Coulter P, Grubb MP, Koyama D, Sazanovich IV, Greetham GM, Orr-Ewing AJ. Recombination, Solvation and Reaction of CN Radicals Following Ultraviolet Photolysis of ICN in Organic Solvents. J Phys Chem A 2015; 119:12911-23. [DOI: 10.1021/acs.jpca.5b10716] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Philip Coulter
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Michael P. Grubb
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Daisuke Koyama
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Igor V. Sazanovich
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot,
Oxfordshire, OX11 0QX, U.K
| | - Gregory M. Greetham
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot,
Oxfordshire, OX11 0QX, U.K
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
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9
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Koyama D, Coulter P, Grubb MP, Greetham GM, Clark IP, Orr-Ewing AJ. Reaction Dynamics of CN Radicals in Acetonitrile Solutions. J Phys Chem A 2015; 119:12924-34. [DOI: 10.1021/acs.jpca.5b10720] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daisuke Koyama
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Philip Coulter
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Michael P. Grubb
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Gregory M. Greetham
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Ian P. Clark
- Central
Laser Facility, Research Complex at Harwell, Science and Technology
Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Andrew J. Orr-Ewing
- School
of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
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10
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Dunning GT, Preston TJ, Greaves SJ, Greetham GM, Clark IP, Orr-Ewing AJ. Vibrational Excitation of Both Products of the Reaction of CN Radicals with Acetone in Solution. J Phys Chem A 2015; 119:12090-101. [PMID: 26192334 PMCID: PMC4685429 DOI: 10.1021/acs.jpca.5b05624] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Transient electronic and vibrational absorption spectroscopy unravel the mechanisms and dynamics of bimolecular reactions of CN radicals with acetone in deuterated chloroform solutions. The CN radicals are produced by ultrafast ultraviolet photolysis of dissolved ICN. Two reactive forms of CN radicals are distinguished by their electronic absorption bands: "free" (uncomplexed) CN radicals, and "solvated" CN radicals that are complexed with solvent molecules. The lifetimes of the free CN radicals are limited to a few picoseconds following their photolytic production because of geminate recombination to ICN and INC, complexation with CDCl3 molecules, and reaction with acetone. The acetone reaction occurs with a rate coefficient of (8.0 ± 0.5) × 10(10) M(-1) s(-1) and transient vibrational spectra in the C═N and C═O stretching regions reveal that both the nascent HCN and 2-oxopropyl (CH3C(O)CH2) radical products are vibrationally excited. The rate coefficient for the reaction of solvated CN with acetone is 40 times slower than for free CN, with a rate coefficient of (2.0 ± 0.9) × 10(9) M(-1) s(-1) obtained from the rise in the HCN product v1(C═N stretch) IR absorption band. Evidence is also presented for CN complexes with acetone that are more strongly bound than the CN-CDCl3 complexes because of CN interactions with the carbonyl group. The rates of reactions of these more strongly associated radicals are slower still.
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Affiliation(s)
- Greg T Dunning
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Thomas J Preston
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
| | - Stuart J Greaves
- School of Engineering and Physical Sciences, Heriot-Watt University , Edinburgh EH14 4AS, U.K
| | - Gregory M Greetham
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory , Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Ian P Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory , Harwell Oxford, Didcot, Oxfordshire OX11 0QX, U.K
| | - Andrew J Orr-Ewing
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
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11
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Mereshchenko AS, Butaeva EV, Borin VA, Eyzips A, Tarnovsky AN. Roaming-mediated ultrafast isomerization of geminal tri-bromides in the gas and liquid phases. Nat Chem 2015; 7:562-8. [DOI: 10.1038/nchem.2278] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 05/09/2015] [Indexed: 11/09/2022]
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12
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Thallmair S, Zauleck JPP, de Vivie-Riedle R. Quantum Dynamics in an Explicit Solvent Environment: A Photochemical Bond Cleavage Treated with a Combined QD/MD Approach. J Chem Theory Comput 2015; 11:1987-95. [DOI: 10.1021/acs.jctc.5b00046] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sebastian Thallmair
- Department
Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
- Lehrstuhl
für BioMolekulare Optik, Ludwig-Maximilians-Universität München, D-80538 München, Germany
| | - Julius P. P. Zauleck
- Department
Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
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13
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Affiliation(s)
- Andrew J. Orr-Ewing
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom;
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14
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Orr-Ewing AJ. Perspective: Bimolecular chemical reaction dynamics in liquids. J Chem Phys 2014; 140:090901. [PMID: 24606343 DOI: 10.1063/1.4866761] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bimolecular reactions in the gas phase exhibit rich and varied dynamical behaviour, but whether a profound knowledge of the mechanisms of isolated reactive collisions can usefully inform our understanding of reactions in liquid solutions remains an open question. The fluctuating environment in a liquid may significantly alter the motions of the reacting particles and the flow of energy into the reaction products after a transition state has been crossed. Recent experimental and computational studies of exothermic reactions of CN radicals with organic molecules indicate that many features of the gas-phase dynamics are retained in solution. However, observed differences may also provide information on the ways in which a solvent modifies fundamental chemical mechanisms. This perspective examines progress in the use of time-resolved infra-red spectroscopy to study reaction dynamics in liquids, discusses how existing theories can guide the interpretation of experimental data, and suggests future challenges for this field of research.
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Affiliation(s)
- Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
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15
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Thallmair S, Kowalewski M, Zauleck JPP, Roos MK, de Vivie-Riedle R. Quantum Dynamics of a Photochemical Bond Cleavage Influenced by the Solvent Environment: A Dynamic Continuum Approach. J Phys Chem Lett 2014; 5:3480-3485. [PMID: 26278596 DOI: 10.1021/jz501718t] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In every day chemistry, solvents are used to influence the outcome of chemical synthesis. Electrostatic effects stabilize polar configurations during the reaction and in addition dynamic solvent effects can emerge. How the dynamic effects intervene on the ultrafast time scale is in the focus of this theoretical study. We selected the photoinduced bond cleavage of Ph2CH-PPh3(+) for which the electrostatic interactions are negligible. Elaborate ultrafast pump-probe studies already exist and serve as a reference. We compared quantum dynamical simulations with and without environment and noticed the necessity to model the influence of the solvent cage on the reactive motions of the solute. The frictional force induced by the dynamic viscosity of the solvent is implemented in the quantum mechanical formalism with a newly developed approach called the dynamic continuum ansatz. Only when the environment is included are the experimentally observed products reproduced on the subpicosecond time scale.
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Affiliation(s)
- Sebastian Thallmair
- †Department Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
- ‡Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München, D-80538 München, Germany
| | - Markus Kowalewski
- †Department Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
| | - Julius P P Zauleck
- †Department Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
| | - Matthias K Roos
- †Department Chemie, Ludwig-Maximilians-Universität München, D-81377 München, Germany
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16
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Opoku-Agyeman B, Case AS, Lehman JH, Lineberger WC, McCoy AB. Nonadiabatic photofragmentation dynamics of BrCN-. J Chem Phys 2014; 141:084305. [PMID: 25173012 DOI: 10.1063/1.4892981] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The photofragmentation dynamics of BrCN(-) in the 270-355 nm and the 430-600 nm wavelength regions is explored both experimentally and theoretically. In the case of excitation between 430 nm and 600 nm, it is found that the molecular ion accesses two dissociation channels with a measured 60:40 branching ratio that is nearly constant over this range of photon energies. The dominant product channel corresponds to Br(-) + CN, while the second channel correlates to spin-orbit excited Br(*) with CN(-). A larger wavelength dependence of the branching ratio is observed at shorter wavelengths, where the fraction of Br(-) based products ranges from 80% to 95% at 355 nm and 270 nm, respectively. These branching ratios are reproduced and the mechanisms are explored by quantum dynamics calculations based on ground and excited state potential energy surfaces for BrCN(-), evaluated at the SO-MRCISD level of theory. It is found that the electronic states that correlate to the two observed product channels are coupled through the spin-orbit terms in the electronic Hamiltonian. The strength of this coupling displays a strong dependence on the Br-CN angle. Specifically, after promotion to the excited state that is energetically accessible with 430-600 nm photons, it is found that when the wave packet accesses Br-CN separations of between 4 Å and 6 Å, predominantly the Br(-) + CN products are formed when the Br-CN angle is smaller than 120°. For larger values of the Br-CN angle, the Br(*) + CN(-) channel dominates. At the shorter wavelength excitation, the dynamics is complicated by a pair of states that correlate to electronically excited CN(*) + Br(-) products that borrow oscillator strength from the bright state, leading to an increase in the amount of Br(-) relative to CN(-). The implications of these findings are discussed and compared to the experimentally measured product branching ratios for the photodissociation of BrCN(-).
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Affiliation(s)
- Bernice Opoku-Agyeman
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Amanda S Case
- JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - Julia H Lehman
- JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - W Carl Lineberger
- JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | - Anne B McCoy
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
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17
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Dunning GT, Preston TJ, Orr-Ewing AJ, Greaves SJ, Greetham GM, Clark IP, Towrie M. Dynamics of photodissociation of XeF2 in organic solvents. Phys Chem Chem Phys 2014; 16:16095-102. [DOI: 10.1039/c4cp01854k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This article explores photodissociation of XeF2 in solution, using femtosecond pump probe spectroscopy to follow the fates of photoproducts following cleavage of one Xe–F bond.
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Affiliation(s)
| | | | | | - Stuart J. Greaves
- School of Engineering and Physical Sciences
- Heriot-Watt University
- Edinburgh EH14 4AS, UK
| | - Gregory M. Greetham
- Central Laser Facility
- Research Complex at Harwell
- Science and Technology Facility Council
- Rutherford Appleton Laboratory
- Harwell Science and Innovation Campus
| | - Ian P. Clark
- Central Laser Facility
- Research Complex at Harwell
- Science and Technology Facility Council
- Rutherford Appleton Laboratory
- Harwell Science and Innovation Campus
| | - Michael Towrie
- Central Laser Facility
- Research Complex at Harwell
- Science and Technology Facility Council
- Rutherford Appleton Laboratory
- Harwell Science and Innovation Campus
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18
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Case AS, McCoy AB, Carl Lineberger W. Dynamics of Small, Ultraviolet-Excited ICN– Cluster Anions. J Phys Chem A 2013; 117:13310-8. [DOI: 10.1021/jp4051758] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Amanda S. Case
- JILA and Department of Chemistry
and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, United States
| | - Anne B. McCoy
- Department of Chemistry and
Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - W. Carl Lineberger
- JILA and Department of Chemistry
and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, United States
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19
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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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Pal SK, Mereshchenko AS, Butaeva EV, El-Khoury PZ, Tarnovsky AN. Global sampling of the photochemical reaction paths of bromoform by ultrafast deep-UV through near-IR transient absorption and ab initio multiconfigurational calculations. J Chem Phys 2013; 138:124501. [DOI: 10.1063/1.4789268] [Citation(s) in RCA: 22] [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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21
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O'Donnell BA, Beames JM, Lester MI. Insights on the CN B 2Σ+ + Ar potential from ultraviolet fluorescence excitation and infrared depletion studies of the CN-Ar complex. J Chem Phys 2012; 136:234303. [PMID: 22779589 DOI: 10.1063/1.4723694] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
UV laser-induced fluorescence and IR-UV fluorescence depletion studies have been used to characterize the intermolecular levels of the CN-Ar complex in the excited state correlating with CN B (2)Σ(+) + Ar. Additional CN-Ar features are identified to lower wavenumber than reported previously. Fluorescence depletion spectra are recorded to confirm that these CN-Ar features and other higher energy features in the B-X spectrum originate from a common ground state level. The UV depletion is induced by IR excitation of CN-Ar from the ground state zero-point level to a hindered internal rotor state (n(K) = 1(1)) in the CN overtone region. The lowest energy feature in the B-X spectrum at 25,714.1 cm(-1) is assigned as a transition to the zero-point level of the B state and also yields its binding energy, D(0) = 186(2) cm(-1), which is in excellent accord with theoretical predictions. The next feature approximately 40 cm(-1) higher is attributed to overlapping transitions to intermolecular levels with bend (v(b)(K)=1(1)) or stretch (v(s) = 1) excitation. Yet higher features (previously reported) are also assigned, based on their transition type and wavenumber, which are consistent with the intermolecular energy level pattern computed theoretically. Finally, the intensity profile of the lowest energy features in the B-X spectrum reflects the predicted change in the CN (B (2)Σ(+), X (2)Σ(+)) + Ar potentials upon electronic excitation from a weakly anisotropic potential about the linear N≡C-Ar configuration in the ground state to a more strongly bound linear C≡N-Ar structure in the excited B electronic state.
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Affiliation(s)
- Bridget A O'Donnell
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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22
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O'Donnell BA, Beames JM, Lester MI. Experimental characterization of the CNX2Σ++ Ar and H2potentials via infrared-ultraviolet double resonance spectroscopy. J Chem Phys 2012; 136:234304. [DOI: 10.1063/1.4723696] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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23
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Dynamic Mapping of CN Rotation Following Photoexcitation of ICN−. Angew Chem Int Ed Engl 2012; 51:2651-3. [DOI: 10.1002/anie.201108025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Indexed: 11/07/2022]
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Case AS, Miller EM, Martin JP, Lu YJ, Sheps L, McCoy AB, Lineberger WC. Dynamic Mapping of CN Rotation Following Photoexcitation of ICN−. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201108025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Miller EM, Sheps L, Lu YJ, Case AS, McCoy AB, Lineberger WC. New view of the ICN A continuum using photoelectron spectroscopy of ICN-. J Chem Phys 2012; 136:044313. [PMID: 22299877 DOI: 10.1063/1.3679170] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Negative-ion photoelectron spectroscopy of ICN(-) (X̃ (2)Σ(+)) reveals transitions to the ground electronic state (X̃ (1)Σ(+)) of ICN as well as the first five excited states ((3)Π(2), (3)Π(1), Π(0(-) ) (3), Π(0(+) ) (3), and (1)Π(1)) that make up the ICN A continuum. By starting from the equilibrium geometry of the anion, photoelectron spectroscopy characterizes the electronic structure of ICN at an elongated I-C bond length of 2.65 Å. Because of this bond elongation, the lowest three excited states of ICN ((3)Π(2), (3)Π(1), and Π(0(-) ) (3)) are resolved for the first time in the photoelectron spectrum. In addition, the spectrum has a structured peak that arises from the frequently studied conical intersection between the Π(0(+) ) (3) and (1)Π(1) states. The assignment of the spectrum is aided by MR-SO-CISD calculations of the potential energy surfaces for the anion and neutral ICN electronic states, along with calculations of the vibrational levels supported by these states. Through thermochemical cycles involving spectrally narrow transitions to the excited states of ICN, we determine the electron affinity, EA(ICN), to be 1.34(5) (+0.04∕-0.02) eV and the anion dissociation energy, D(0)(X̃ (2)Σ(+) I-CN(-)), to be 0.83 (+0.04/-0.02) eV.
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Affiliation(s)
- Elisa M Miller
- JILA, Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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26
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Rose RA, Greaves SJ, Abou-Chahine F, Glowacki DR, Oliver TAA, Ashfold MNR, Clark IP, Greetham GM, Towrie M, Orr-Ewing AJ. Reaction dynamics of CN radicals with tetrahydrofuran in liquid solutions. Phys Chem Chem Phys 2012; 14:10424-37. [DOI: 10.1039/c2cp40158d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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27
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Rose RA, Greaves SJ, Oliver TAA, Clark IP, Greetham GM, Parker AW, Towrie M, Orr-Ewing AJ. Vibrationally quantum-state-specific dynamics of the reactions of CN radicals with organic molecules in solution. J Chem Phys 2011; 134:244503. [DOI: 10.1063/1.3603966] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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28
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Orr-Ewing AJ, Glowacki DR, Greaves SJ, Rose RA. Chemical Reaction Dynamics in Liquid Solutions. J Phys Chem Lett 2011; 2:1139-44. [PMID: 26295316 DOI: 10.1021/jz2002716] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The dynamics of bimolecular chemical reactions can be examined in liquid solutions using infrared absorption spectroscopy with picosecond time resolution. On such short time scales, the transient absorption spectra reveal vibrational mode and quantum-state-specific energy disposal, followed by vibrational relaxation as the energy is dissipated to the surrounding solvent. Comparison with energy disposal measurements for gas-phase reactions under single-collision conditions offers direct insights into the modification of the energy landscape and the nuclear dynamics in the presence of the solvent. The reactions of CN radicals with organic molecules in chlorinated solvents exemplify the dynamical information that can be obtained. The potential to extend such experiments to a range of reactions and solvents is discussed.
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Affiliation(s)
| | - David R Glowacki
- School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K
| | - Stuart J Greaves
- School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K
| | - Rebecca A Rose
- School of Chemistry, University of Bristol, Bristol BS8 1TS, U.K
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29
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Beames JM, O'Donnell BA, Ting M, Lester MI, Stephenson TA. Experimental characterization of the weakly anisotropic CN X 2Σ+ + Ne potential from IR-UV double resonance studies of the CN-Ne complex. J Chem Phys 2011; 134:184308. [PMID: 21568507 DOI: 10.1063/1.3586810] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
IR-UV double resonance spectroscopy has been used to characterize hindered internal rotor states (n(K) = 0(0), 1(1), and 1(0)) of the CN-Ne complex in its ground electronic state with various degrees of CN stretch (ν(CN)) excitation. Rotationally resolved infrared overtone spectra of the CN-Ne complex exhibit perturbations arising from Coriolis coupling between the closely spaced hindered rotor states (1(1) and 1(0)) with two quanta of CN stretch (ν(CN) = 2). A deperturbation analysis is used to obtain accurate rotational constants and associated average CN center-of-mass to Ne separation distances as well as the coupling strength. The energetic ordering and spacings of the hindered internal rotor states provide a direct reflection of the weakly anisotropic intermolecular potential between CN X (2)Σ(+) and Ne, with only an 8 cm(-1) barrier to CN internal rotation, from which radially averaged anisotropy parameters (V(10) and V(20)) are extracted that are consistent for ν(CN) = 0-3. Complementary ab initio calculation of the CN X (2)Σ(+) + Ne potential using MRCI+Q extrapolated to the complete one-electron basis set limit is compared with the experimentally derived anisotropy by optimizing the radial potential at each angle. Experiment and theory are in excellent accord, both indicating a bent minimum energy configuration and nearly free rotor behavior. Analogous experimental and theoretical studies of the CN-Ne complex upon electronic excitation to the CN B (2)Σ(+) state indicate a slightly more anisotropic potential with a linear CN-Ne minimum energy configuration. The results from these IR-UV double resonance studies are compared with prior electronic spectroscopy and theoretical studies of the CN-Ne system.
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Affiliation(s)
- Joseph M Beames
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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30
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Greaves SJ, Rose RA, Oliver TAA, Glowacki DR, Ashfold MNR, Harvey JN, Clark IP, Greetham GM, Parker AW, Towrie M, Orr-Ewing AJ. Vibrationally Quantum-State–Specific Reaction Dynamics of H Atom Abstraction by CN Radical in Solution. Science 2011; 331:1423-6. [DOI: 10.1126/science.1197796] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Stuart J. Greaves
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - Rebecca A. Rose
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - Thomas A. A. Oliver
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - David R. Glowacki
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | | | - Jeremy N. Harvey
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
| | - Ian P. Clark
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Gregory M. Greetham
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Anthony W. Parker
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Michael Towrie
- Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
| | - Andrew J. Orr-Ewing
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
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31
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Rivera CA, Winter N, Harper RV, Benjamin I, Bradforth SE. The dynamical role of solvent on the ICN photodissociation reaction: connecting experimental observables directly with molecular dynamics simulations. Phys Chem Chem Phys 2011; 13:8269-83. [DOI: 10.1039/c1cp20252a] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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32
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Oliver TAA, Zhang Y, Ashfold MNR, Bradforth SE. Linking photochemistry in the gas and solution phase: S–H bond fission in p-methylthiophenol following UV photoexcitation. Faraday Discuss 2011; 150:439-58; discussion 505-32. [DOI: 10.1039/c0fd00031k] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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33
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Johnson ML, Benjamin I. Photodissociation of ICN at the Water/Chloroform Interface. J Phys Chem A 2009; 113:7403-11. [DOI: 10.1021/jp900153j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mindy L. Johnson
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
| | - Ilan Benjamin
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
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34
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Crowther AC, Carrier SL, Preston TJ, Crim FF. Time-Resolved Studies of the Reactions of CN Radical Complexes with Alkanes, Alcohols, and Chloroalkanes. J Phys Chem A 2009; 113:3758-64. [DOI: 10.1021/jp8084099] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andrew C. Crowther
- Department of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706
| | - Stacey L. Carrier
- Department of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706
| | - Thomas J. Preston
- Department of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706
| | - F. Fleming Crim
- Department of Chemistry, University of Wisconsin−Madison, Madison, Wisconsin 53706
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35
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Crowther AC, Carrier SL, Preston TJ, Crim FF. Time-Resolved Studies of CN Radical Reactions and the Role of Complexes in Solution. J Phys Chem A 2008; 112:12081-9. [DOI: 10.1021/jp8064079] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andrew C. Crowther
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
| | - Stacey L. Carrier
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
| | - Thomas J. Preston
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
| | - F. Fleming Crim
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
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36
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Savitzky BH, Stratt RM. Anatomy of an Energy Transfer Event in a Liquid: The High-Energy Rotational Relaxation of OH in Solution. J Phys Chem B 2008; 112:13326-34. [DOI: 10.1021/jp805792e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Richard M. Stratt
- Department of Chemistry, Brown University, Providence, Rhode Island 02912
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37
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Tao G, Stratt RM. Anomalously Slow Solvent Structural Relaxation Accompanying High-Energy Rotational Relaxation. J Phys Chem B 2007; 112:369-77. [DOI: 10.1021/jp075664a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guohua Tao
- Department of Chemistry, Brown University, Providence, Rhode Island 02912
| | - Richard M. Stratt
- Department of Chemistry, Brown University, Providence, Rhode Island 02912
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38
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Gelin MF, Kosov DS. Manifestation of nonequilibrium initial conditions in molecular rotation: The generalized J-diffusion model. J Chem Phys 2007; 127:144511. [DOI: 10.1063/1.2779037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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39
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Gelin MF, Kosov DS. Angular momentum dependent friction slows down rotational relaxation under nonequilibrium conditions. J Chem Phys 2007; 125:224502. [PMID: 17176144 DOI: 10.1063/1.2401609] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
It has recently been shown that relaxation of the rotational energy of hot nonequilibrium photofragments (i) slows down significantly with the increase of their initial rotational temperature and (ii) differs dramatically from the relaxation of the equilibrium rotational energy correlation function, manifesting thereby the breakdown of the linear response description [A. C. Moskun et al., Science 311, 1907 (2006)]. We demonstrate that this phenomenon may be caused by the angular momentum dependence of rotational friction. We have developed the generalized Fokker-Planck equation whose rotational friction depends upon angular momentum algebraically. The calculated rotational correlation functions correspond well to their counterparts obtained via molecular dynamics simulations in a broad range of initial nonequilibrium conditions. It is suggested that the angular momentum dependence of friction should be taken into account while describing rotational relaxation far from equilibrium.
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Affiliation(s)
- M F Gelin
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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40
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Tao G, Stratt RM. The molecular origins of nonlinear response in solute energy relaxation: The example of high-energy rotational relaxation. J Chem Phys 2006; 125:114501. [PMID: 16999484 DOI: 10.1063/1.2336780] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A key step in solution-phase chemical reactions is often the removal of excess internal energy from the product. Yet, the way one typically studies this process is to follow the relaxation of a solute that has been excited into some distribution of excited states quite different from that produced by any reaction of interest. That the effects of these different excitations can frequently be ignored is a consequence of the near universality of linear-response behavior, the idea that relaxation dynamics is determined by the solvent fluctuations (which may not be all that different for different kinds of solute excitation). Nonetheless, there are some clear examples of linear-response breakdowns seen in solute relaxation, including a recent theoretical and experimental study of rapidly rotating diatomics in liquids. In this paper we use this rotational relaxation example to carry out a theoretical exploration of the conditions that lead to linear-response failure. Some features common to all of the linear-response breakdowns studied to date, including our example, are that the initial solute preparation is far from equilibrium, that the subsequent relaxation promotes a significant rearrangement of the liquid structure, and that the nonequilibrium response is nonstationary. However, we show that none of these phenomena is enough to guarantee a nonlinear response. One also needs a sufficient separation between the solute time scale and that of the solvent geometry evolution. We illustrate these points by demonstrating precisely how our relaxation rate is tied to our liquid-structural evolution, how we can quantitatively account for the initial nonstationarity of our effective rotational friction, and how one can tune our rotational relaxation into and out of linear response.
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Affiliation(s)
- Guohua Tao
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
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41
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Moskun AC, Bradforth SE, Thøgersen J, Keiding S. Absence of a Signature of Aqueous I(2P1/2) after 200-nm Photodetachment of I-(aq). J Phys Chem A 2006; 110:10947-55. [PMID: 16986827 DOI: 10.1021/jp053992+] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ultrafast pump-broadband probe spectroscopy was used to study the transient photoproducts following 200-nm photodetachment of I(-)(aq). Resonant detachment at 200 nm in the second charge-transfer-to-solvent (CTTS) band of I(-)(aq) is expected to produce an electron and iodine in its spin-orbit excited state, I*((2)P(1/2)). The transients in solution following photodetachment were probed from 200 to 620 nm. Along with strong absorption in the visible region due to solvated electrons and a strong bleach of the I(-)(aq) ground-state absorption, a weaker transient absorption near 260 nm was observed that is consistent with a previously assigned ground-state I((2)P(3/2)) charge-transfer band. However, no evidence was found for an equivalent I*(aq) charge-transfer absorption, and I((2)P(3/2)) was produced within the instrument response. This suggests either that I* is electronically relaxed in less than 300 fs or that excitation in the second CTTS band does not in fact lead to I*. The consequences for previous experimental work where I*(aq) production has been postulated, as well as for halogen electron ejection mechanisms, are discussed. In addition, the broad spectral coverage of this study reveals in the bleach recovery the rapid cooling of the solvent surrounding the re-formed iodide after geminate recombination of the iodine with the solvated electron.
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Affiliation(s)
- Amy C Moskun
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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Abstract
▪ Abstract Modern ultrafast spectroscopic techniques provide new opportunities to study chemical reaction dynamics in liquids and hold the possibility of obtaining much of the same detailed information available in gases. Vibrational energy transfer studies are the most advanced of the investigations and demonstrate that it is possible to observe state-specific pathways of energy flow within a vibrationally excited molecule (intramolecular vibrational relaxation) and into the surrounding solvent molecules (intermolecular energy transfer). Energy transfer in liquids and gases share many common aspects, but the presence of the solvent also alters the relaxation in both obvious and subtle ways. Photodissociation is amenable to similarly detailed study in liquids, and there are informative new measurements. Bimolecular reactions have received the least attention in state-resolved measurements in liquids, but the means to carry them much further now exist. Studying photodissociation and bimolecular reaction of molecules prepared with initial vibrational excitation in liquids is a realistic, but challenging, goal.
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Affiliation(s)
- Christopher G Elles
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
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Moskun AC, Jailaubekov AE, Bradforth SE, Tao G, Stratt RM. Rotational Coherence and a Sudden Breakdown in Linear Response Seen in Room-Temperature Liquids. Science 2006; 311:1907-11. [PMID: 16574863 DOI: 10.1126/science.1123738] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Highly energized molecules normally are rapidly equilibrated by a solvent; this finding is central to the conventional (linear-response) view of how chemical reactions occur in solution. However, when a reaction initiated by 33-femtosecond deep ultraviolet laser pulses is used to eject highly rotationally excited diatomic molecules into alcohols and water, rotational coherence persists for many rotational periods despite the solvent. Molecular dynamics simulations trace this slow development of molecular-scale friction to a clearly identifiable molecular event: an abrupt liquid-structure change triggered by the rapid rotation. This example shows that molecular relaxation can sometimes switch from linear to nonlinear response.
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Affiliation(s)
- Amy C Moskun
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
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44
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Pieniazek PA, Bradforth SE, Krylov AI. Spectroscopy of the Cyano Radical in an Aqueous Environment. J Phys Chem A 2006; 110:4854-65. [PMID: 16599455 DOI: 10.1021/jp0545952] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effect of bulk water on the B (2)Sigma(+) <-- X (2)Sigma(+) and A (2)Pi <-- X (2)Sigma(+) electronic transitions of the cyano radical is investigated. First, the cyano radical-water dimer is characterized to understand the nature of the interactions and parametrize molecular mechanics (MM) potentials. The carbon atom, which hosts the unpaired electron, is found to have a Lennard-Jones radius smaller than typical force fields values. Classical molecular dynamics (MD) is then used to sample water configurations around the radical, employing two sets of MM parameters for the cyano radical and water. Subsequently, vertical excitation energies are calculated using time-dependent density functional theory (TD-DFT) and equation-of-motion coupled-cluster with single and double substitutions (EOM-CCSD). The effect of water is modeled by point charges used in the MD simulations. It is found that both bands blue-shift with respect to their gas phase position; the magnitude of the shift is only weakly dependent on the method and the MM parameter set used. The calculated shifts are analyzed in terms of the solute-solvent interactions in the ground and excited states. Significant contributions come from valence repulsion and electrostatics. Consequences for experiments on ICN photodissociation in water are discussed.
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Affiliation(s)
- Piotr A Pieniazek
- Department of Chemistry, University of Southern California, Los Angeles, 90089-0482, USA
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Elles CG, Cox MJ, Barnes GL, Crim FF. Recombination and Reaction Dynamics Following Photodissociation of CH3OCl in Solution. J Phys Chem A 2004. [DOI: 10.1021/jp046627b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher G. Elles
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
| | - M. Jocelyn Cox
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
| | - George L. Barnes
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
| | - F. Fleming Crim
- Department of Chemistry, University of Wisconsin − Madison, Madison, Wisconsin 53706
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Knappenberger KL, Castleman AW. The influence of cluster formation on the photodissociation of sulfur dioxide: Excitation to the E state. J Chem Phys 2004; 121:3540-9. [PMID: 15303919 DOI: 10.1063/1.1767091] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A femtosecond pump-probe technique was employed to study the dissociation dynamics of sulfur dioxide and sulfur dioxide clusters in real time. Dissociation is initiated by a multiphoton scheme that populates the E state. The SO(2) (+) transient is fit to a biexponential decay comprising a fast and a slow component of 230 fs and 8 ps, respectively. The SO(+) transient consists of a growth component of 225 fs as well as a subsequent decay of 373 fs. The pump-probe response obtained from the monomer clearly shows the predissociative cleavage of a S-O bond. Upon cluster formation, a sequential increase in the fast decay component is observed for increasing cluster size, extending to 435 fs for (SO(2))(4) (+). The transient response of cluster dissociation products SO(SO(2))(n) (+), where n=1-3, reflects no growth component indicating that formation proceeds through the ion state. Therefore, cluster formation results in a caging effect, which impedes the dissociation process. Further direct evidence for our proposed mechanism is obtained by a technique that employs a comparison of the amplitude coefficients of each respective component of the fit. This method makes possible the determination of branching ratios of competing relaxation processes and thereby the influence of cluster formation on each can be resolved. The caging effect is attributed to a steric hindrance placed on the SO(2) chromophore, preventing it from attaining a linear geometry necessary for dissociation.
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Affiliation(s)
- K L Knappenberger
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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