1
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Cigrang LLE, Worth GA. Modeling Photodissociation: Quantum Dynamics Simulations of Methanol. J Phys Chem A 2024; 128:7546-7557. [PMID: 39194169 PMCID: PMC11403662 DOI: 10.1021/acs.jpca.4c03612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2024]
Abstract
A comprehensive computational study of the gas-phase photodissociation dynamics of methanol is presented. Using a multiconfigurational active space based method (RASSCF) to obtain multidimensional potential energy surfaces (PESs) on-the-fly, direct quantum dynamics simulations were run using the variational multi-configurational Gaussian method (DD-vMCG). Different initial excitation energies were simulated to investigate the dependence of the branching ratios on the electronic state being populated. A detailed mechanistic explanation is provided for the observed differences with respect to the excitation energy. Population of the lowest lying excited state of methanol leads to rapid hydroxyl hydrogen loss as the main dissociation channel. This is rationalized by the strongly dissociative nature of the PES cut along the O-H stretching coordinate, confirmed by the broad feature in the absorption spectrum. In contrast, more energetic excitations lead mainly to C-O bond breaking. Again, analysis of the diabatic surfaces offers a clear explanation in terms of the nature of the electronic states involved and the coupling between them. The type of calculations presented, as well as the subsequent analysis of the results, should be seen as a general workflow for the modeling of photochemical reactions.
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Affiliation(s)
- Léon L E Cigrang
- Department of Chemistry, University College London, London WC1H 0AJ, United Kingdom
| | - Graham A Worth
- Department of Chemistry, University College London, London WC1H 0AJ, United Kingdom
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2
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Fuchs S, Dick B. Photodissociation of deuterated pyrrole-ammonia clusters: H-atom transfer or electron coupled proton transfer? Phys Chem Chem Phys 2024; 26:14514-14528. [PMID: 38629346 DOI: 10.1039/d4cp00566j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Several years ago the discovery of a conical intersection offered an explanation for the ultafast photodissociation of pyrrole. Subsequently, the photodissociation of pyrrole ammonia complexes PyH*(NH3)n with n ≥ 3 was studied in the gas phase as a model for a hydrogen-bond forming solvent. Two alternative mechanisms, electron coupled proton transfer (ECPT) and hydrogen atom transfer (HAT, also called the impulsive model, IM), have been proposed. The parent 1 : 1 complex was never studied, due to the short lifetime of the NH4 radical fragment. Here we report experiments on the deuterated species PyD*(ND3)n, including the 1 : 1 complex (n = 1). The velocity distribution of the ND4 radical is well approximated by a Maxwell-Boltzmann distribution of T ≈ 530 K, with a negative anisotropy parameter of β = -0.3. The impulsive model predicts a much narrower velocity distribution with larger negative anisotropy. The ECPT model predicts a long lived intermediate that should allow thermal equilibration of the vibrational energy but should also destroy the rotational memory of the initially excited state. The average kinetic energy agrees with the prediction of the impulsive model, whereas the wide range of kinetic energies is more in line with ECPT. Hence the mechanism seems to be more complex and requires further theoretical modelling.
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Affiliation(s)
- Stefan Fuchs
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
| | - Bernhard Dick
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany.
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3
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Zhang Z, Wu H, Chen Z, Fu Y, Fu B, Zhang DH, Yang X, Yuan K. Multiple Dissociation Pathways in HNCO Decomposition Governed by Potential Energy Surface Topography. JACS AU 2023; 3:2855-2861. [PMID: 37885590 PMCID: PMC10598830 DOI: 10.1021/jacsau.3c00414] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/24/2023] [Accepted: 08/31/2023] [Indexed: 10/28/2023]
Abstract
The exquisite features of molecular photochemistry are key to any complete understanding of the chemical processes governed by potential energy surfaces (PESs). It is well established that multiple dissociation pathways relate to nonadiabatic transitions between multiple coupled PESs. However, little detail is known about how the single PES determines reaction outcomes. Here we perform detailed experiments on HNCO photodissociation, acquiring the state-specific correlations of the NH (a1Δ) and CO (X1Σ+) products. The experiments reveal a trimodal CO rotational distribution. Dynamics simulations based on a full-dimensional machine-learning-based PES of HNCO unveil three dissociation pathways exclusively occurring on the S1 excited electronic state. One pathway, following the minimum energy path (MEP) via the transition state, contributes to mild rotational excitation in CO, while the other two pathways deviating substantially from the MEP account for relatively cold and hot CO rotational state populations. These peculiar dynamics are unambiguously governed by the S1 state PES topography, i.e., a narrow acceptance cone in the vicinity of the transition state region. The dynamical picture shown in this work will serve as a textbook example illustrating the importance of the PES topography in molecular photochemistry.
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Affiliation(s)
- Zhiguo Zhang
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- Key
Laboratory of Functional Materials and Devices for Informatics of
Anhui Educational Institutions and School of Physics and Electronic
Engineering, Fuyang Normal University, Fuyang, Anhui 236041, China
| | - Hao Wu
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhichao Chen
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Yanlin Fu
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
| | - Bina Fu
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
- Hefei
National Laboratory, Hefei 230088, China
| | - Dong H. Zhang
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
- Hefei
National Laboratory, Hefei 230088, China
| | - Xueming Yang
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
- Hefei
National Laboratory, Hefei 230088, China
- Department
of Chemistry and Center for Advanced Light Source Research, College
of Science, Southern University of Science
and Technology, Shenzhen 518055, China
| | - Kaijun Yuan
- State
Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent
Light Source, Dalian Institute of Chemical
Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, P. R. China
- Hefei
National Laboratory, Hefei 230088, China
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4
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Champenois EG, List NH, Ware M, Britton M, Bucksbaum PH, Cheng X, Centurion M, Cryan JP, Forbes R, Gabalski I, Hegazy K, Hoffmann MC, Howard AJ, Ji F, Lin MF, Nunes JPF, Shen X, Yang J, Wang X, Martinez TJ, Wolf TJA. Femtosecond Electronic and Hydrogen Structural Dynamics in Ammonia Imaged with Ultrafast Electron Diffraction. PHYSICAL REVIEW LETTERS 2023; 131:143001. [PMID: 37862660 DOI: 10.1103/physrevlett.131.143001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 07/06/2023] [Accepted: 08/12/2023] [Indexed: 10/22/2023]
Abstract
Directly imaging structural dynamics involving hydrogen atoms by ultrafast diffraction methods is complicated by their low scattering cross sections. Here we demonstrate that megaelectronvolt ultrafast electron diffraction is sufficiently sensitive to follow hydrogen dynamics in isolated molecules. In a study of the photodissociation of gas phase ammonia, we simultaneously observe signatures of the nuclear and corresponding electronic structure changes resulting from the dissociation dynamics in the time-dependent diffraction. Both assignments are confirmed by ab initio simulations of the photochemical dynamics and the resulting diffraction observable. While the temporal resolution of the experiment is insufficient to resolve the dissociation in time, our results represent an important step towards the observation of proton dynamics in real space and time.
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Affiliation(s)
- Elio G Champenois
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Nanna H List
- Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Matthew Ware
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Mathew Britton
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Philip H Bucksbaum
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Xinxin Cheng
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Martin Centurion
- Department of Physics and Astronomy, University of Nebraska Lincoln, Lincoln, Nebraska 68588, USA
| | - James P Cryan
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Ruaridh Forbes
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Ian Gabalski
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Kareem Hegazy
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | | | - Andrew J Howard
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Fuhao Ji
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Ming-Fu Lin
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - J Pedro F Nunes
- Department of Physics and Astronomy, University of Nebraska Lincoln, Lincoln, Nebraska 68588, USA
| | - Xiaozhe Shen
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Jie Yang
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Xijie Wang
- SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Todd J Martinez
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Thomas J A Wolf
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
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5
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Kim J, Woo KC, Kang M, Kim SK. Dynamic Role of the Intramolecular Hydrogen Bonding in the S 1 State Relaxation Dynamics Revealed by the Direct Measurement of the Mode-Dependent Internal Conversion Rate of 2-Chlorophenol and 2-Chlorothiophenol. J Phys Chem Lett 2023; 14:8428-8436. [PMID: 37712655 DOI: 10.1021/acs.jpclett.3c02208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/16/2023]
Abstract
The dynamic role of the intramolecular hydrogen bond in the S1 relaxation of cis-2-chlorophenol (2-CP) or cis-2-chlorothiophenol (2-CTP) has been investigated in a state-specific manner. Whereas ultrafast internal conversion is dominant for 2-CP, the H-tunneling competes with internal conversion for 2-CTP even at the S1 origin. The S0-S1 internal conversion rate of 2-CTP could be directly measured from the S1 lifetimes of 2-CTP-d1 (Cl-C6H4-SD) as the D-tunneling is kinetically blocked, allowing distinct estimations of tunneling and internal conversion rates with increasing the energy. The internal conversion rate of 2-CTP increases by two times at the out-of-plane torsional mode excitation, suggesting that the internal conversion is facilitated at the nonplanar geometry. It then sharply increases at ∼600 cm-1, indicating that the S1/S0 conical intersection is readily accessible at the extended C-Cl bond length. The strength of the intramolecular hydrogen bond should be responsible for the distinct dynamic behaviors of 2-CP and 2-CTP.
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Affiliation(s)
- Junggil Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Kyung Chul Woo
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Minseok Kang
- 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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6
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Chang Y, Ashfold MNR, Yuan K, Yang X. Exploring the vacuum ultraviolet photochemistry of astrochemically important triatomic molecules. Natl Sci Rev 2023; 10:nwad158. [PMID: 37771464 PMCID: PMC10533343 DOI: 10.1093/nsr/nwad158] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 11/03/2022] [Accepted: 02/08/2023] [Indexed: 09/30/2023] Open
Abstract
The recently constructed vacuum ultraviolet (VUV) free electron laser (FEL) at the Dalian Coherent Light Source (DCLS) is yielding a wealth of new and exquisitely detailed information about the photofragmentation dynamics of many small gas-phase molecules. This Review focuses particular attention on five triatomic molecules-H2O, H2S, CO2, OCS and CS2. Each shows excitation wavelength-dependent dissociation dynamics, yielding photofragments that populate a range of electronic and (in the case of diatomic fragments) vibrational and rotational quantum states, which can be characterized by different translational spectroscopy methods. The photodissociation of an isolated molecule from a well-defined initial quantum state provides a lens through which one can investigate how and why chemical reactions occur, and provides numerous opportunities for fruitful, synergistic collaborations with high-level ab initio quantum chemists. The chosen molecules, their photofragments and the subsequent chemical reaction networks to which they can contribute are all crucial in planetary atmospheres and in interstellar and circumstellar environments. The aims of this Review are 3-fold: to highlight new photochemical insights enabled by the VUV-FEL at the DCLS, notably the recently recognized central atom elimination process that is shown to contribute in all of these triatomic molecules; to highlight some of the potential implications of this rich photochemistry to our understanding of interstellar chemistry and molecular evolution within the universe; and to highlight other and future research directions in areas related to chemical reaction dynamics and astrochemistry that will be enabled by increased access to VUV-FEL sources.
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Affiliation(s)
- Yao Chang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | | | - Kaijun Yuan
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Hefei National Laboratory, Hefei 230088, China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
- Hefei National Laboratory, Hefei 230088, China
- Department of Chemistry, College of Science, Southern University of Science and Technology, Shenzhen 518055, China
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7
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Crane SW, Lee JWL, Ashfold MNR, Rolles D. Molecular photodissociation dynamics revealed by Coulomb explosion imaging. Phys Chem Chem Phys 2023. [PMID: 37335247 DOI: 10.1039/d3cp01740k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Coulomb explosion imaging (CEI) methods are finding ever-growing use as a means of exploring and distinguishing the static stereo-configurations of small quantum systems (molecules, clusters, etc). CEI experiments initiated by ultrafast (femtosecond-duration) laser pulses also allow opportunities to track the time-evolution of molecular structures, and thereby advance understanding of molecular fragmentation processes. This Perspective illustrates two emerging families of dynamical studies. 'One-colour' studies (employing strong field ionisation driven by intense near infrared or single X-ray or extreme ultraviolet laser pulses) afford routes to preparing multiply charged molecular cations and exploring how their fragmentation progresses from valence-dominated to Coulomb-dominated dynamics with increasing charge and how this evolution varies with molecular size and composition. 'Two-colour' studies use one ultrashort laser pulse to create electronically excited neutral molecules (or monocations), whose structural evolution is then probed as a function of pump-probe delay using an ultrafast ionisation pulse along with time and position-sensitive detection methods. This latter type of experiment has the potential to return new insights into not just molecular fragmentation processes but also charge transfer processes between moieties separating with much better defined stereochemical control than in contemporary ion-atom and ion-molecule charge transfer studies.
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Affiliation(s)
- Stuart W Crane
- School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK.
| | - Jason W L Lee
- Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK
| | | | - Daniel Rolles
- J.R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506, USA
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8
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Kim J, Woo KC, Kim SK. Mode-dependent H atom tunneling dynamics of the S 1 phenol is resolved by the simple topographic view of the potential energy surfaces along the conical intersection seam. J Chem Phys 2023; 158:104301. [PMID: 36922134 DOI: 10.1063/5.0143655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
Mode-dependent H atom tunneling dynamics of the O-H bond predissociation of the S1 phenol has been theoretically analyzed. As the tunneling is governed by the complicated multi-dimensional potential energy surfaces that are dynamically shaped by the upper-lying S1(ππ*)/S2(πσ*) conical intersection, the mode-specific tunneling dynamics of phenol (S1) has been quite formidable to be understood. Herein, we have examined the topography of the potential energy surface along the particular S1 vibrational mode of interest at the nuclear configurations of the S1 minimum and S1/S2 conical intersection. The effective adiabatic tunneling barrier experienced by the reactive flux at the particular S1 vibrational mode excitation is then uniquely determined by the topographic shape of the potential energy surface extended along the conical intersection seam coordinate associated with the particular vibrational mode. The resultant multi-dimensional coupling of the specific vibrational mode to the tunneling coordinate is then reflected in the mode-dependent tunneling rate as well as nonadiabatic transition probability. Remarkably, the mode-specific experimental result of the S1 phenol tunneling reaction [K. C. Woo and S. K. Kim, J. Phys. Chem. A 123, 1529-1537 (2019)] (in terms of the qualitative and relative mode-dependent dynamic behavior) could be well rationalized by semi-classical calculations based on the mode-specific topography of the effective tunneling barrier, providing the clear conceptual insight that the skewed potential energy surfaces along the conical intersection seam (strongly or weakly coupled to the tunneling reaction coordinate) may dictate the tunneling dynamics in the proximity of the conical intersection.
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Affiliation(s)
- Junggil Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
| | - Kyung Chul Woo
- 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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Roque JPL, Rosado MTS, Fausto R, Reva I. Dual Photochemistry of Benzimidazole. J Org Chem 2023; 88:2884-2897. [PMID: 36795993 PMCID: PMC9990075 DOI: 10.1021/acs.joc.2c02560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Monomers of benzimidazole trapped in an argon matrix at 15 K were characterized by vibrational spectroscopy and identified as 1H-tautomers exclusively. The photochemistry of matrix-isolated 1H-benzimidazole was induced by excitations with a frequency-tunable narrowband UV light and followed spectroscopically. Hitherto unobserved photoproducts were identified as 4H- and 6H-tautomers. Simultaneously, a family of photoproducts bearing the isocyano moiety was identified. Thereby, the photochemistry of benzimidazole was hypothesized to follow two reaction pathways: the fixed-ring and the ring-opening isomerizations. The former reaction channel results in the cleavage of the NH bond and formation of a benzimidazolyl radical and an H-atom. The latter reaction channel involves the cleavage of the five-membered ring and concomitant shift of the H-atom from the CH bond of the imidazole moiety to the neighboring NH group, leading to 2-isocyanoaniline and subsequently to the isocyanoanilinyl radical. The mechanistic analysis of the observed photochemistry suggests that detached H-atoms, in both cases, recombine with the benzimidazolyl or isocyanoanilinyl radicals, predominantly at the positions with the largest spin density (revealed using the natural bond analysis computations). The photochemistry of benzimidazole therefore occupies an intermediate position between the earlier studied prototype cases of indole and benzoxazole, which exhibit exclusively the fixed-ring and the ring-opening photochemistries, respectively.
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Affiliation(s)
- José P L Roque
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
| | - Mário T S Rosado
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
| | - Rui Fausto
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal
| | - Igor Reva
- CQC-IMS, Department of Chemistry, University of Coimbra, Coimbra 3004-535, Portugal.,CIEPQPF, Department of Chemical Engineering, University of Coimbra, Coimbra 3030-790, Portugal
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10
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Tureček F. UV-vis spectroscopy of gas-phase ions. MASS SPECTROMETRY REVIEWS 2023; 42:206-226. [PMID: 34392556 DOI: 10.1002/mas.21726] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 06/13/2023]
Abstract
Photodissociation action spectroscopy has made a great progress in expanding investigations of gas-phase ion structures. This review deals with aspects of gas-phase ion electronic excitations that result in wavelength-dependent dissociation and light emission via fluorescence, chiefly covering the ultraviolet and visible regions of the spectrum. The principles are briefly outlined and a few examples of instrumentation are presented. The main thrust of the review is to collect and selectively present applications of UV-vis action spectroscopy to studies of stable gas-phase ion structures and combinations of spectroscopy with ion mobility, collision-induced dissociation, and ion-ion reactions leading to the generation of reactive intermediates and electronic energy transfer.
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Affiliation(s)
- František Tureček
- Department of Chemistry, University of Washington, Seattle, Washington, USA
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11
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Radiationless deactivation pathways versus H-atom elimination from the N-H bond photodissociation in PhNH 2-(Py) n (n = 1,2) complexes. PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES : OFFICIAL JOURNAL OF THE EUROPEAN PHOTOCHEMISTRY ASSOCIATION AND THE EUROPEAN SOCIETY FOR PHOTOBIOLOGY 2023; 22:33-45. [PMID: 36071272 DOI: 10.1007/s43630-022-00295-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/19/2022] [Indexed: 01/12/2023]
Abstract
Minimum energy structures of the ground and lowest excited states of aniline (PhNH2) solvated by pyridine (Py) show that the clusters formed are stabilized by hydrogen bonds in which only one or both hydrogen atoms of the NH2 group take part. Two different N-H bonds photodissociation in PhNH2-(Py)n (n = 1,2) complexes, free and hydrogen bonded have been studied by analyzing excited state potential energy surfaces. In the first one, only N-H bonds engaged in hydrogen bonding in these complexes are considered. RICC2 calculations of potential energy (PE) profiles indicate that all photochemical reaction paths along N-H stretching occur mainly via the proton-coupled electron transfer (PCET) mechanism. The repulsive charge transfer 1ππ*(CT) state dominates the PE profiles, leading to low-lying 1ππ*(CT)/S0 conical intersections and thus provide channels for ultrafast radiationless deactivation of the electronic excitation or stabilization to biradical complexes. The second photoreaction consists of a direct dissociation along the free N-H bond of the NH2 group. It has been shown that this process is played by excited singlet states of 1πσ* character having repulsive potential energy profiles with respect to the stretching of N-H bond, which dissociates over an exit barrier about 0.5 eV giving rise to the formation of a 1πσ*/S0 conical intersection. This may cause an internal conversion to the ground state or may lead to H-atom elimination. This photophysical process is the same in both planar and T-shaped conformers of the PhNH2-Py monomer complex. Our findings reveal that there is no single dominating path in the photodissociation of N-H bonds in PhNH2-(Py)n complexes, but rather a variety of paths involving H-atom elimination and several quenching mechanisms.
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12
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Kim J, Woo KC, Kim KK, Kim SK. πσ*-Mediated Nonadiabatic Tunneling Dynamics of Thiophenols in S 1: The Semiclassical Approaches. J Phys Chem A 2022; 126:9594-9604. [PMID: 36534791 DOI: 10.1021/acs.jpca.2c05861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The S-H bond tunneling predissociation dynamics of thiophenol and its ortho-substituted derivatives (2-fluorothiophenol, 2-methoxythiophenol, and 2-chlorothiphenol) in S1 (ππ*) where the H atom tunneling is mediated by the nearby S2 (πσ*) state (which is repulsive along the S-H bond extension coordinate) have been investigated in a state-specific way using the picosecond time-resolved pump-probe spectroscopy for the jet-cooled molecules. The effects of the specific vibrational mode excitations and the SH/SD substitutions on the S-H(D) bond rupture tunneling dynamics have been interrogated, giving deep insights into the multidimensional aspects of the S1/S2 conical intersection, which also shapes the underlying adiabatic tunneling potential energy surfaces (PESs). The semiclassical tunneling rate calculations based on the Wentzel-Kramers-Brillouin (WKB) approximation or Zhu-Nakamura (ZN) theory have been carried out based on the ab initio PESs calculated in the (one, two, or three) reduced dimensions to be compared with the experiment. Though the quantitative experimental results could not be reproduced satisfactorily by the present calculations, the qualitative trends among different molecules in terms of the behavior of the tunneling rate versus the (adiabatic) barrier height or the number of PES dimensions could be rationalized. Most interestingly, the H/D kinetic isotope effect observed in the tunneling rate could be much better explained by the ZN theory compared to the WKB approximation, indicating that the nonadiabatic coupling matrix elements should be invoked for understanding the tunneling dynamics taking place in the proximity of the conical intersection.
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Affiliation(s)
- Junggil Kim
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
| | - Kyung Chul Woo
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
| | - Kuk Ki Kim
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon34141, Republic of Korea
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13
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Chen J, Chen F, Wang X, Zhao Y, Wu Y, Cao Q, Jiang T, Li K, Li Y, Zhang J, Wu W, Che R. Room-Temperature Response Performance of Coupled Doped-Well Quantum Cascade Detectors with Array Structure. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 13:110. [PMID: 36616020 PMCID: PMC9824534 DOI: 10.3390/nano13010110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/23/2022] [Accepted: 12/24/2022] [Indexed: 06/17/2023]
Abstract
Energy level interaction and electron concentration are crucial aspects that affect the response performance of quantum cascade detectors (QCDs). In this work, two different-structured array QCDs are prepared, and the detectivity reaches 109 cm·Hz1/2/W at room temperature. The overlap integral (OI) and oscillator strength (OS) between different energy levels under a series of applied biases are fitted and reveal the influence of energy level interaction on the response performance. The redistribution of electrons in the cascade structure at room temperatures is established. The coupled doped-well structure shows a higher electron concentration at room temperature, which represents a high absorption efficiency in the active region. Even better responsivity and detectivity are exhibited in the coupled doped-well QCD. These results offer a novel strategy to understand the mechanisms that affect response performance and expand the application range of QCDs for long-wave infrared (LWIR) detection.
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Affiliation(s)
- Jie Chen
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, China
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | - Fengwei Chen
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | - Xuemin Wang
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | - Yunhao Zhao
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, China
| | - Yuyang Wu
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, China
| | - Qingchen Cao
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, China
| | - Tao Jiang
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | - Keyu Li
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | - Yang Li
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | | | - Weidong Wu
- Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China
| | - Renchao Che
- Laboratory of Advanced Materials, Shanghai Key Lab of Molecular Catalysis and Innovative Materials, Academy for Engineering & Technology, Fudan University, Shanghai 200438, China
- Zhejiang Laboratory, Hangzhou 311100, China
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14
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Kotsina N, Jackson SL, Malcomson T, Paterson MJ, Townsend D. Photochemical carbon-sulfur bond cleavage in thioethers mediated via excited state Rydberg-to-valence evolution. Phys Chem Chem Phys 2022; 24:29423-29436. [PMID: 36453640 DOI: 10.1039/d2cp04789f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Time-resolved photoelectron imaging and supporting ab initio quantum chemistry calculations were used to investigate non-adiabatic excess energy redistribution dynamics operating in the saturated thioethers diethylsulfide, tetrahydrothiophene and thietane. In all cases, 200 nm excitation leads to molecular fragmentation on an ultrafast (<100 fs) timescale, driven by the evolution of Rydberg-to-valence orbital character along the S-C stretching coordinate. The C-S-C bending angle was also found to be a key coordinate driving initial internal conversion through the excited state Rydberg manifold, although only small angular displacements away from the ground state equilibrium geometry are required. Conformational constraints imposed by the cyclic ring structures of tetrahydrothiophene and thietane do not therefore influence dynamical timescales to any significant extent. Through use of a high-intensity 267 nm probe, we were also able to detect the presence of some transient (bi)radical species. These are extremely short lived, but they appear to confirm the presence of two competing excited state fragmentation channels - one proceeding directly from the initially prepared 4p manifold, and one involving non-adiabatic population of the 4s state. This is in addition to a decay pathway leading back to the S0 electronic ground state, which shows an enhanced propensity in the 5-membered ring system tetrahydrothiophene over the other two species investigated.
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Affiliation(s)
- Nikoleta Kotsina
- Institute of Photonics & Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK
| | - Sebastian L Jackson
- Institute of Photonics & Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK
| | - Thomas Malcomson
- Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Martin J Paterson
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
| | - Dave Townsend
- Institute of Photonics & Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.,Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
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15
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The role of predissociation states in the UV photooxidation of acetylene. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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16
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Waters MDJ, Wörner HJ. The ultrafast vibronic dynamics of ammonia's D̃ state. Phys Chem Chem Phys 2022; 24:23340-23349. [PMID: 36129030 DOI: 10.1039/d2cp03117e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using vacuum-ultraviolet time-resolved velocity map imaging of photoelectrons, we study ultrafast coupled electronic and nuclear dynamics in low-lying Rydberg states of ammonia. Vibrationally-resolved internal vibrational relaxation (IVR) is observed in a progression of the e' bending modes. This vibrational progression is only observed in the D̃ state, and is lost upon ultrafast internal conversion to the C̃ and B̃ electronic states. Due to the ultrashort time scale of the internal conversion (ca. 64 fs), and the vibronic resolution, the non-adiabatic coupling vectors are identified and verified with ab initio calculations. The time-scale of this IVR process is highly surprising and significant because IVR is usually treated as an incoherent process that proceeds statistically, according to a "Fermi's Golden Rule"-like model, where the process scales with the available degrees of freedom. Here, we show that it can be highly non-statistical, restricted to only a very small subset of vibrational motions.
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Affiliation(s)
- Max D J Waters
- Laboratory for Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland.
| | - Hans Jakob Wörner
- Laboratory for Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland.
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17
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Han S, Schröder M, Gatti F, Meyer HD, Lauvergnat D, Yarkony DR, Guo H. Representation of Diabatic Potential Energy Matrices for Multiconfiguration Time-Dependent Hartree Treatments of High-Dimensional Nonadiabatic Photodissociation Dynamics. J Chem Theory Comput 2022; 18:4627-4638. [PMID: 35839299 DOI: 10.1021/acs.jctc.2c00370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Conventional quantum mechanical characterization of photodissociation dynamics is restricted by steep scaling laws with respect to the dimensionality of the system. In this work, we examine the applicability of the multi-configurational time-dependent Hartree (MCTDH) method in treating nonadiabatic photodissociation dynamics in two prototypical systems, taking advantage of its favorable scaling laws. To conform to the sum-of-product form, elements of the ab initio diabatic potential energy matrix (DPEM) are re-expressed using the recently proposed Monte Carlo canonical polyadic decomposition method, with enforcement of proper symmetry. The MCTDH absorption spectra and product branching ratios are shown to compare well with those calculated using conventional grid-based methods, demonstrating its promise for treating high-dimensional nonadiabatic photodissociation problems.
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Affiliation(s)
- Shanyu Han
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Markus Schröder
- Theoretische Chemie, Physikalisch Chemisches Institut, Ruprecht-Karls Universität Heidelberg, D-69120 Heidelberg, Germany
| | - Fabien Gatti
- ISMO, Institut des Sciences Moléculaires d'Orsay─UMR 8214 CNRS/Université Paris-Saclay, F-91405 Orsay, France
| | - Hans-Dieter Meyer
- Theoretische Chemie, Physikalisch Chemisches Institut, Ruprecht-Karls Universität Heidelberg, D-69120 Heidelberg, Germany
| | - David Lauvergnat
- Université Paris-Saclay, CNRS, Institut de Chimie Physique UMR8000, Orsay 91405, France
| | - David R Yarkony
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
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18
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Ashfold MNR, Kim SK. Non-Born-Oppenheimer effects in molecular photochemistry: an experimental perspective. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2022; 380:20200376. [PMID: 35341307 DOI: 10.1098/rsta.2020.0376] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 06/28/2021] [Indexed: 06/14/2023]
Abstract
Non-adiabatic couplings between Born-Oppenheimer (BO)-derived potential energy surfaces are now recognized as pivotal in describing the non-radiative decay of electronically excited molecules following photon absorption. This opinion piece illustrates how non-BO effects provide photostability to many biomolecules when exposed to ultraviolet radiation, yet in many other cases are key to facilitating 'reactive' outcomes like isomerization and bond fission. The examples are presented in order of decreasing molecular complexity, spanning studies of organic sunscreen molecules in solution, through two families of heteroatom containing aromatic molecules and culminating with studies of isolated gas phase H2O molecules that afford some of the most detailed insights yet available into the cascade of non-adiabatic couplings that enable the evolution from photoexcited molecule to eventual products. This article is part of the theme issue 'Chemistry without the Born-Oppenheimer approximation'.
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Affiliation(s)
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea
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19
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Pios S, Domcke W. Ab Initio Electronic Structure Study of the Photoinduced Reduction of Carbon Dioxide with the Heptazinyl Radical. J Phys Chem A 2022; 126:2778-2787. [PMID: 35476421 DOI: 10.1021/acs.jpca.2c00615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photocatalytic conversion of carbon dioxide to liquid fuels with electrons taken from water with solar photons is one of the grand goals of renewable energy research. Polymeric carbon nitrides recently emerged as metal-free materials with promising functionalities for hydrogen evolution from water as well as the activation of carbon dioxide. Molecular heptazine (Hz), the building block of polymeric carbon nitrides, is one the strongest known organic photo-oxidants and has been shown to be able to photo-oxidize water with near-visible light, resulting in reduced (hydrogenated) heptazine (HzH) and OH radicals. In the present work, we explored with ab initio computational methods whether the HzH chromophore is able to reduce carbon dioxide to the hydroxy-formyl (HOCO) radical in hydrogen-bonded HzH-CO2 complexes by the absorption of a photon. In remarkable contrast to the high barrier for carbon dioxide activation in the electronic ground state, the excited-state proton-coupled electron transfer (PCET) reaction is nearly barrierless, but requires the diabatic passage of three conical intersections. The possibility of barrierless carbon dioxide activation by excited-state PCET has so far not been taken into consideration in the interpretation of photocatalytic carbon dioxide reduction on carbon nitride materials.
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Affiliation(s)
- Sebastian Pios
- Department of Chemistry, Technical University of Munich, D-85747 Garching, Germany
| | - Wolfgang Domcke
- Department of Chemistry, Technical University of Munich, D-85747 Garching, Germany
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20
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Lapinski L, Rostkowska H, Nowak MJ. Distinct class of photoinduced hydrogen-atom-transfer processes: phototautomerizations in molecules with no intramolecular hydrogen bond in the structure. INT REV PHYS CHEM 2022. [DOI: 10.1080/0144235x.2022.2030613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Leszek Lapinski
- Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Hanna Rostkowska
- Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Maciej J. Nowak
- Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
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21
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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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22
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Li C, Hou S, Xie C. Three-dimensional diabatic potential energy surfaces of thiophenol with neural networks. CHINESE J CHEM PHYS 2021. [DOI: 10.1063/1674-0068/cjcp2110196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Chaofan Li
- Institute of Modern Physics, Northwest University, Xi’an 710127, China
- Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi’an 710127, China
| | - Siting Hou
- Institute of Modern Physics, Northwest University, Xi’an 710127, China
- Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi’an 710127, China
| | - Changjian Xie
- Institute of Modern Physics, Northwest University, Xi’an 710127, China
- Shaanxi Key Laboratory for Theoretical Physics Frontiers, Xi’an 710127, China
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23
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Huang X, Domcke W. Ab Initio Nonadiabatic Surface-Hopping Trajectory Simulations of Photocatalytic Water Oxidation and Hydrogen Evolution with the Heptazine Chromophore. J Phys Chem A 2021; 125:9917-9931. [PMID: 34748705 DOI: 10.1021/acs.jpca.1c08291] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the past decade, polymeric carbon nitrides consisting of heptazine (Hz) building blocks emerged as highly promising materials for photocatalytic hydrogen evolution from water or sacrificial electron donors with near-ultraviolet light. However, the complexity of these materials and their poor characterization at the atomic level are detrimental to the unraveling of the detailed mechanisms of the reactions leading to hydrogen evolution. Recently, it has been shown that a derivative of the Hz molecule, trianisole-heptazine (TAHz), is a potent photobase, which readily oxidizes various derivatives of phenol and even water by an excited-state proton-coupled electron-transfer (PCET) reaction. Energy profiles along minimum-energy reaction paths and relaxed PCET potential-energy surfaces, which previously were computed with ab initio electronic-structure methods for complexes of Hz and TAHz with protic substrates, led to qualitative insights. To obtain more quantitative insight, reaction dynamics simulations are required. In the present work, the time scales of the electron and proton transfer processes and the branching ratios of competing channels were explored with ab initio on-the-fly quasiclassical surface-hopping trajectory simulations for the hydrogen-bonded Hz-H2O complex. By the analysis of representative trajectories, detailed insight into the interplay of various nonadiabatic electronic transitions, electron transfer, proton transfer, and vibrational energy relaxation is obtained. The HzH radicals which are formed by the photoreduction of Hz can disproportionate to Hz and HzH2 in an exothermic reaction with a low reaction barrier. The time scales and branching ratios of competing channels in H-atom photodetachment from the HzH2 molecule also were explored with ab initio surface-hopping simulations. These results delineate for the first time a quantitatively supported scenario of water oxidation and hydrogen evolution with a molecular carbon nitride photocatalyst.
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Affiliation(s)
- Xiang Huang
- Department of Chemistry, Technical University of Munich, Garching D-85747, Germany
| | - Wolfgang Domcke
- Department of Chemistry, Technical University of Munich, Garching D-85747, Germany
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24
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Karas LJ, Wu CH, Wu JI. Barrier-Lowering Effects of Baird Antiaromaticity in Photoinduced Proton-Coupled Electron Transfer (PCET) Reactions. J Am Chem Soc 2021; 143:17970-17974. [PMID: 34672631 DOI: 10.1021/jacs.1c09324] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Many popular organic chromophores that catalyze photoinduced proton-coupled electron transfer (PCET) reactions are aromatic in the ground state but become excited-state antiaromatic in the lowest ππ* state. We show that excited-state antiaromaticity makes electron transfer easier. Two representative photoinduced electron transfer processes are investigated: (1) the photolysis of phenol and (2) solar water splitting of a pyridine-water complex. In the selected reactions, the directions of electron transfer are opposite, but the net result is proton transfer following the direction of electron transfer. Nucleus-independent chemical shifts (NICS), ionization energies, electron affinities, and PCET energy profiles of selected [4n] and [4n + 2] π-systems are presented, and important mechanistic implications are discussed.
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Affiliation(s)
- Lucas J Karas
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Chia-Hua Wu
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
| | - Judy I Wu
- Department of Chemistry, University of Houston, Houston, Texas 77204, United States
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25
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26
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Affiliation(s)
- Sahil Gulania
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Anna I. Krylov
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
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27
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Kim KK, Kim J, Woo KC, Kim SK. S 1-State Decay Dynamics of Benzenediols (Catechol, Resorcinol, and Hydroquinone) and Their 1:1 Water Clusters. J Phys Chem A 2021; 125:7655-7661. [PMID: 34432455 DOI: 10.1021/acs.jpca.1c05448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The S1-state decaying rates of the three different benzenediols, catechol, resorcinol, and hydroquinone, and their 1:1 water clusters have been state-specifically measured using the picosecond time-resolved parent ion transients obtained by the pump (excitation) and probe (ionization) scheme. The S1 lifetime of catechol is found to be short, giving τ ∼ 5.9 ps at the zero-point level. This is ascribed to the H-atom detachment from the free OH moiety of the molecule. Consistent with a previous report (J. Phys. Chem. Lett. 2013, 4, 3819-3823), the S1 lifetime gets lengthened with low-frequency vibrational mode excitations, giving τ ∼ 9.0 ps for the 116 cm-1 band. The S1 lifetimes at the additional vibronic modes of catechol are newly measured, showing the nonnegligible mode-dependent fluctuations of the tunneling rate. When catechol is complexed with water, the S1 lifetime is enormously increased to τ ∼ 1.80 ns at the zero-point level while it shows an unusual dip at the intermolecular stretching mode excitation (τ ∼ 1.03 ns at 146 cm-1). Otherwise, it is shortened monotonically with increasing the internal energy, giving τ ∼ 0.67 ns for the 856 cm-1 band. Two different asymmetric or symmetric conformers of resorcinol give the respective S1 lifetimes of 4.5 or 6.3 ns at their zero-point levels according to the estimation from our transients taken within the temporal window of 0-2.7 ns. When resorcinol is 1:1 complexed with H2O, the S1 decaying rate is slightly accelerated for both conformers. The S1 lifetimes of trans and cis forms of hydroquinone are measured to be more or less same, giving τ ∼ 2.8 ns at the zero-point level. When H2O is complexed with hydroquinone, the S1 decaying process is facilitated for both conformers, slightly more efficiently for the cis conformer.
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Affiliation(s)
- Kuk Ki Kim
- Department of Chemistry, KAIST, Dajeon 34141, Republic of Korea
| | - Junggil Kim
- Department of Chemistry, KAIST, Dajeon 34141, Republic of Korea
| | - Kyung Chul Woo
- Department of Chemistry, KAIST, Dajeon 34141, Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST, Dajeon 34141, Republic of Korea
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28
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Rostkowska H, Luchowska A, Lapinski L, Nowak MJ. Effect of a Solid-Hydrogen Environment on UV-Induced Hydrogen-Atom Transfer in Matrix-Isolated Heterocyclic Thione Compounds. J Phys Chem A 2021; 125:7437-7448. [PMID: 34406775 PMCID: PMC8419844 DOI: 10.1021/acs.jpca.1c05538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
To shed more light
on the mechanisms of UV-induced hydrogen-atom-transfer
processes in heterocyclic molecules, phototautomeric thione →
thiol reactions were investigated for thione compounds isolated in
low-temperature Ar as well as in n-H2 (normal hydrogen)
matrices. These studies concerned thione compounds with a five-membered
heterocyclic ring and thione compounds with a six-membered heterocyclic
ring. The experimental investigation of 2-thioimidazole and 3-thio-1,2,4-triazole
(thione compounds with a five-membered heterocyclic ring) revealed
that for the compounds isolated in solid n-H2 only trace
amounts of thiol photoproducts were photogenerated; even though for
the same compounds isolated in the solid Ar matrix, the thione → thiol photoconversion
was nearly
total. In contrast to that, for 3-thiopyridazine and 2-thioquinoline
(thione compounds with a six-membered heterocyclic
ring) isolated in solid n-H2, the UV-induced thione →
thiol conversion occurred with the yield reaching 25–50% of
the yield of the analogous process observed for the same species isolated
in solid Ar. The obtained experimental results allow us to conclude
that the dissociation–association mechanism nearly exclusively
governs the phototransformation in thione heterocycles with high barriers
for tautomerization (such as thione compounds with a five-membered
ring), whereas the strictly intramolecular hydrogen-atom shift contributes
to the mechanism of hydrogen-atom transfer in thione heterocycles
with lower barriers (such as thione compounds with a six-membered
ring).
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Affiliation(s)
- Hanna Rostkowska
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Anna Luchowska
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Leszek Lapinski
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Maciej J Nowak
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
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29
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Han S, Sun G, Zheng X, Song Y, Dawes R, Xie D, Zhang J, Guo H. Rotational Modulation of Ã2A″-State Photodissociation of HCO via Renner-Teller Nonadiabatic Transitions. J Phys Chem Lett 2021; 12:6582-6588. [PMID: 34242507 DOI: 10.1021/acs.jpclett.1c01932] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
By examining the product-state distribution of a prototypical nonadiabatic predissociation system, HCO(Ã2A″-X̃2A'), we demonstrate that the dissociation dynamics is strongly modulated by parent rotational quantum numbers. The predissociation of the nominal (νC-H = 0, νbend, νC-O = 1) vibronic levels of the Ã2A″ state surprisingly gives rise to both vibrational ground and excited states of the CO product, despite the assumed spectator nature of the CO moiety. This anomaly is attributed to the dependence of the lifetime of the vibronic resonance facilitated by the Renner-Teller interaction on the parent rotational angular momentum quantum numbers coupled with transient intensity borrowing from nearby vibronic resonances with νC-O = 0. This unique phenomenon is a purely quantum mechanical behavior that has no classical analogue.
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Affiliation(s)
- Shanyu Han
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Ge Sun
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Xianfeng Zheng
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
- Anhui Province Key Laboratory of Optoelectric Materials Science and Technology, Department of Physics, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Yu Song
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Richard Dawes
- Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, 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
| | - Jingsong Zhang
- Department of Chemistry, University of California Riverside, Riverside, California 92521, United States
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
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30
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Jadoun D, Gudem M, Kowalewski M. Capturing fingerprints of conical intersection: Complementary information of non-adiabatic dynamics from linear x-ray probes. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:034101. [PMID: 33981781 PMCID: PMC8096460 DOI: 10.1063/4.0000093] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 04/08/2021] [Indexed: 05/09/2023]
Abstract
Many recent experimental ultrafast spectroscopy studies have hinted at non-adiabatic dynamics indicating the existence of conical intersections, but their direct observation remains a challenge. The rapid change of the energy gap between the electronic states complicated their observation by requiring bandwidths of several electron volts. In this manuscript, we propose to use the combined information of different x-ray pump-probe techniques to identify the conical intersection. We theoretically study the conical intersection in pyrrole using transient x-ray absorption, time-resolved x-ray spontaneous emission, and linear off-resonant Raman spectroscopy to gather evidence of the curve crossing.
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Affiliation(s)
- Deependra Jadoun
- Department of Physics, Stockholm University, Albanova University Centre, SE-106 91 Stockholm, Sweden
| | - Mahesh Gudem
- Department of Physics, Stockholm University, Albanova University Centre, SE-106 91 Stockholm, Sweden
| | - Markus Kowalewski
- Department of Physics, Stockholm University, Albanova University Centre, SE-106 91 Stockholm, Sweden
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31
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Pagacz-Kostrzewa M, Kochman M, Gul W, Wierzejewska M. Phototransformations of 2-aminonicotinic acid resolved with matrix isolation infrared spectroscopy and ab initio calculations. J Photochem Photobiol A Chem 2021. [DOI: 10.1016/j.jphotochem.2021.113187] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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32
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Karbalaei Khani S, Geissler B, Engelage E, Nuernberger P, Hättig C. Tracing absorption and emission characteristics of halogen-bonded ion pairs involving halogenated imidazolium species. Phys Chem Chem Phys 2021; 23:7480-7494. [PMID: 33876108 DOI: 10.1039/d1cp00009h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We investigate how the absorption and fluorescence of halogenated imidazolium compounds in acetonitrile solution is influenced by the presence of counterions and the ability to act as halogen-bond donors. Experimental measurements and quantum chemical calculations with correlated wavefunction methods are applied to study three monodentate halogen-bond complexes of iodo-imidazolium, iodo-benzimidazolium and bromo-benzimidazolium cations with triflate counterions, and a bidentate complex of bis(iodo-benzimidazolium) dications with chloride as counterion. The three monodentate complexes with triflate counterions relax after photoexcitation to minima on the S1 potential energy surface where the C-I bond and the IO halogen bond are partially broken. For the bidentate complex with the smaller chloride counterion the halogen-bond interaction stays intact in the S1 minimum that is reached by relaxation from the Franck-Condon point. In a complementing experimental approach, stationary absorption and emission as well as transient fluorescence spectra are recorded for iodo- and bromo-benzimidazolium in acetonitrile. Variation of the counterion, substitution of the iodine by bromine, hydrogen, or methyl, and the comparison to theory allows the identification of spectroscopic signatures and photoinduced dynamics associated with ion-pairing.
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33
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Gudem M, Kowalewski M. Controlling the Photostability of Pyrrole with Optical Nanocavities. J Phys Chem A 2021; 125:1142-1151. [PMID: 33464084 PMCID: PMC7883346 DOI: 10.1021/acs.jpca.0c09252] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/15/2020] [Indexed: 11/28/2022]
Abstract
Strong light-matter coupling provides a new strategy to manipulate the non-adiabatic dynamics of molecules by modifying potential energy surfaces. The vacuum field of nanocavities can couple strongly with the molecular degrees of freedom and form hybrid light-matter states, termed as polaritons or dressed states. The photochemistry of molecules possessing intrinsic conical intersections can be significantly altered by introducing cavity couplings to create new conical intersections or avoided crossings. Here, we explore the effects of optical cavities on the photo-induced hydrogen elimination reaction of pyrrole. Wave packet dynamics simulations have been performed on the two-state, two-mode model of pyrrole, combined with the cavity photon mode. Our results show how the optical cavities assist in controlling the photostability of pyrrole and influence the reaction mechanism by providing alternative dissociation pathways. The cavity effects have been found to be intensely dependent on the resonance frequency. We further demonstrate the importance of the vibrational cavity couplings and dipole-self interaction terms in describing the cavity-modified non-adiabatic dynamics.
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Affiliation(s)
- Mahesh Gudem
- Department of Physics, Albanova University
Centre, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Markus Kowalewski
- Department of Physics, Albanova University
Centre, Stockholm University, SE-106 91 Stockholm, Sweden
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34
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Jouvet C, Miyazaki M, Fujii M. Revealing the role of excited state proton transfer (ESPT) in excited state hydrogen transfer (ESHT): systematic study in phenol-(NH 3) n clusters. Chem Sci 2021; 12:3836-3856. [PMID: 34163653 PMCID: PMC8179502 DOI: 10.1039/d0sc06877b] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Excited State Hydrogen Transfer (ESHT), proposed at the end of the 20th century by the corresponding authors, has been observed in many neutral or protonated molecules and become a new paradigm to understand excited state dynamics/photochemistry of aromatic molecules. For example, a significant number of photoinduced proton-transfer reactions from X–H bonds have been re-defined as ESHT, including those of phenol, indole, tryptophan, aromatic amino acid cations and so on. Photo-protection mechanisms of biomolecules, such as isolated nucleic acids of DNA, are also discussed in terms of ESHT. Therefore, a systematic and up-to-date description of ESHT mechanism is important for researchers in chemistry, biology and related fields. In this review, we will present a general model of ESHT which unifies the excited state proton transfer (ESPT) and the ESHT mechanisms and reveals the hidden role of ESPT in controlling the reaction rate of ESHT. For this purpose, we give an overview of experimental and theoretical work on the excited state dynamics of phenol–(NH3)n clusters and related molecular systems. The dynamics has a significant dependence on the number of solvent molecules in the molecular cluster. Three-color picosecond time-resolved IR/near IR spectroscopy has revealed that ESHT becomes an electron transfer followed by a proton transfer in highly solvated clusters. The systematic change from ESHT to decoupled electron/proton transfer according to the number of solvent molecules is rationalized by a general model of ESHT including the role of ESPT. A general model of excited state hydrogen transfer (ESHT) which unifies ESHT and the excited state proton transfer (ESPT) is presented from experimental and theoretical works on phenol–(NH3)n. The hidden role of ESPT is revealed.![]()
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Affiliation(s)
- Christophe Jouvet
- CNRS, Aix Marseille Université, Physique des Interactions Ioniques et Moleculaires (PIIM), UMR 7345 13397 Marseille Cedex France .,World Research Hub Initiatives, Institute of Innovative Research, Tokyo Institute of Technology 4259-R1-15, Nagatsuta-cho, Midori-ku Yokohama 226-8503 Japan
| | - Mitsuhiko Miyazaki
- Natural Science Division, Faculty of Core Research, Ochanomizu University 2-1-1 Ohtsuka, Bunkyo-ku Tokyo 112-8610 Japan.,Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology 4259-R1-15, Nagatsuta-cho, Midori-ku Yokohama 226-8503 Japan
| | - Masaaki Fujii
- World Research Hub Initiatives, Institute of Innovative Research, Tokyo Institute of Technology 4259-R1-15, Nagatsuta-cho, Midori-ku Yokohama 226-8503 Japan.,Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology 4259-R1-15, Nagatsuta-cho, Midori-ku Yokohama 226-8503 Japan
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35
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Jiang LL, Song YF, Liu WL, Wu HL, Li XY, Yang YQ. Ultrafast characteristics of vibrational dynamics in tetrahydrofuran via femtosecond coherent anti-stokes Raman scattering. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2020.138256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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36
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Vallance C, Heathcote D, Lee JWL. Covariance-Map Imaging: A Powerful Tool for Chemical Dynamics Studies. J Phys Chem A 2021; 125:1117-1133. [DOI: 10.1021/acs.jpca.0c10038] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Claire Vallance
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - David Heathcote
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Jason W. L. Lee
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
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37
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Kotsina N, Townsend D. Improved insights in time-resolved photoelectron imaging. Phys Chem Chem Phys 2021; 23:10736-10755. [DOI: 10.1039/d1cp00933h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We review new light source developments and data analysis considerations relevant to the time-resolved photoelectron imaging technique. Case studies illustrate how these themes may enhance understanding in studies of excited state molecular dynamics.
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Affiliation(s)
- Nikoleta Kotsina
- Institute of Photonics & Quantum Sciences
- Heriot-Watt University
- Edinburgh
- UK
| | - Dave Townsend
- Institute of Photonics & Quantum Sciences
- Heriot-Watt University
- Edinburgh
- UK
- Institute of Chemical Sciences
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38
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Léger SJ, Marchetti B, Ashfold MNR, Karsili TNV. The Role of Norrish Type-I Chemistry in Photoactive Drugs: An ab initio Study of a Cyclopropenone-Enediyne Drug Precursor. Front Chem 2020; 8:596590. [PMID: 33425854 PMCID: PMC7793749 DOI: 10.3389/fchem.2020.596590] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/25/2020] [Indexed: 01/01/2023] Open
Abstract
We present a contemporary mechanistic description of the light-driven conversion of cyclopropenone containing enediyne (CPE) precusors to ring-opened species amenable to further Bergman cyclization and formation of stable biradical species that have been proposed for use in light-induced cancer treatment. The transformation is rationalized in terms of (purely singlet state) Norrish type-I chemistry, wherein photoinduced opening of one C-C bond in the cyclopropenone ring facilitates non-adiabatic coupling to high levels of the ground state, subsequent loss of CO and Bergman cyclization of the enediyne intermediate to the cytotoxic target biradical species. Limited investigations of substituent effects on the ensuing photochemistry serve to vindicate the experimental choices of Popik and coworkers (J. Org. Chem., 2005, 70, 1297-1305). Specifically, replacing the phenyl moiety in the chosen model CPE by a 1,4-benzoquinone unit leads to a stronger, red-shifted parent absorption, and increases the exoergicity of the parent → biradical conversion.
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Affiliation(s)
- Spencer J. Léger
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA, United States
- Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA, United States
| | - Barbara Marchetti
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA, United States
| | | | - Tolga N. V. Karsili
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA, United States
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39
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Gao H. Molecular photodissociation in the vacuum ultraviolet region: implications for astrochemistry and planetary atmospheric chemistry. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1861354] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
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40
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Paterson MJ, Townsend D. Rydberg-to-valence evolution in excited state molecular dynamics. INT REV PHYS CHEM 2020. [DOI: 10.1080/0144235x.2020.1815389] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
| | - Dave Townsend
- Institute of Chemical Sciences, Heriot-Watt University, Edinburgh, UK
- Institute of Photonics & Quantum Sciences, Heriot-Watt University, Edinburgh, UK
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41
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Domcke W, Sobolewski AL, Schlenker CW. Photooxidation of water with heptazine-based molecular photocatalysts: Insights from spectroscopy and computational chemistry. J Chem Phys 2020; 153:100902. [PMID: 32933269 DOI: 10.1063/5.0019984] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a conspectus of recent joint spectroscopic and computational studies that provided novel insight into the photochemistry of hydrogen-bonded complexes of the heptazine (Hz) chromophore with hydroxylic substrate molecules (water and phenol). It was found that a functionalized derivative of Hz, tri-anisole-heptazine (TAHz), can photooxidize water and phenol in a homogeneous photochemical reaction. This allows the exploration of the basic mechanisms of the proton-coupled electron-transfer (PCET) process involved in the water photooxidation reaction in well-defined complexes of chemically tunable molecular chromophores with chemically tunable substrate molecules. The unique properties of the excited electronic states of the Hz molecule and derivatives thereof are highlighted. The potential energy landscape relevant for the PCET reaction has been characterized by judicious computational studies. These data provided the basis for the demonstration of rational laser control of PCET reactions in TAHz-phenol complexes by pump-push-probe spectroscopy, which sheds light on the branching mechanisms occurring by the interaction of nonreactive locally excited states of the chromophore with reactive intermolecular charge-transfer states. Extrapolating from these results, we propose a general scenario that unravels the complex photoinduced water-splitting reaction into simple sequential light-driven one-electron redox reactions followed by simple dark radical-radical recombination reactions.
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Affiliation(s)
- Wolfgang Domcke
- Department of Chemistry, Technical University of Munich, D-85747 Garching, Germany
| | | | - Cody W Schlenker
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
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42
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Revealing electronic state-switching at conical intersections in alkyl iodides by ultrafast XUV transient absorption spectroscopy. Nat Commun 2020; 11:4042. [PMID: 32788648 PMCID: PMC7423985 DOI: 10.1038/s41467-020-17745-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 07/06/2020] [Indexed: 11/11/2022] Open
Abstract
Conical intersections between electronic states often dictate the chemistry of photoexcited molecules. Recently developed sources of ultrashort extreme ultraviolet (XUV) pulses tuned to element-specific transitions in molecules allow for the unambiguous detection of electronic state-switching at a conical intersection. Here, the fragmentation of photoexcited iso-propyl iodide and tert-butyl iodide molecules (i-C3H7I and t-C4H9I) through a conical intersection between 3Q0/1Q1 spin–orbit states is revealed by ultrafast XUV transient absorption measuring iodine 4d core-to-valence transitions. The electronic state-sensitivity of the technique allows for a complete mapping of molecular dissociation from photoexcitation to photoproducts. In both molecules, the sub-100 fs transfer of a photoexcited wave packet from the 3Q0 state into the 1Q1 state at the conical intersection is captured. The results show how differences in the electronic state-switching of the wave packet in i-C3H7I and t-C4H9I directly lead to differences in the photoproduct branching ratio of the two systems. The reaction trajectories of photoexcited molecules may involve transitions through conical intersections, which are ubiquitous in nature but challenging to characterize. Here the authors provide a complete mapping of molecular dissociation of two model alkyl halides by ultrafast XUV transient absorption.
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43
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He C, Yin R, Hu G, Zhou X, Chen Y, Zhao D, Jiang B. Combined experimental and theoretical study on the ultraviolet photodissociation dynamics of 1-bromo-2,6-difluorobenzene in 267 nm-234 nm. J Chem Phys 2020; 153:034305. [PMID: 32716193 DOI: 10.1063/5.0010823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Thanks to their specific molecular symmetry, aromatic molecules and their derivatives represent ideal model systems in understanding photo-induced chemistry of small molecules. Herein, ultraviolet photodissociation dynamics of the 1-bromo-2,6-difluorobenzene molecule has been visualized via imaging the recoiling velocity distributions of photofragments. The measured recoiling angular distributions of the Br(2P3/2) product vary significantly with the increasing photon energy, arguing against the simple bond-fission mechanism within the C2v symmetry. Ab initio calculations reveal that in addition to the C-Br bond cleavage, two additional internal molecular coordinates that break the molecular symmetry are likely involved. The Br out-of-plane bending opens a direct dissociation pathway on the S1-1A″ (S1-1ππ*) state, while the asymmetric C-F stretching significantly changes the orientation of the transition dipole moment. The present study sheds new light on the effect of symmetry breaking in the photodissociation dynamics of symmetric aryl halides, highlighting the multi-dimensional feature of excited state potential energy surfaces.
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Affiliation(s)
- Chao He
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Rongrong Yin
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Gaoming Hu
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xueyao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yang Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Dongfeng Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Bin Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
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44
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Ultraviolet photolysis of H 2S and its implications for SH radical production in the interstellar medium. Nat Commun 2020; 11:1547. [PMID: 32210241 PMCID: PMC7093389 DOI: 10.1038/s41467-020-15343-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/05/2020] [Indexed: 11/27/2022] Open
Abstract
Hydrogen sulfide radicals in the ground state, SH(X), and hydrogen disulfide molecules, H2S, are both detected in the interstellar medium, but the returned SH(X)/H2S abundance ratios imply a depletion of the former relative to that predicted by current models (which assume that photon absorption by H2S at energies below the ionization limit results in H + SH photoproducts). Here we report that translational spectroscopy measurements of the H atoms and S(1D) atoms formed by photolysis of jet-cooled H2S molecules at many wavelengths in the range 122 ≤ λ ≤155 nm offer a rationale for this apparent depletion; the quantum yield for forming SH(X) products, Γ, decreases from unity (at the longest excitation wavelengths) to zero at short wavelengths. Convoluting the wavelength dependences of Γ, the H2S parent absorption and the interstellar radiation field implies that only ~26% of photoexcitation events result in SH(X) products. The findings suggest a need to revise the relevant astrochemical models. Sulfur is abundant in the Universe, but the observed abundance ratio of SH to H2S doesn’t agree with astrochemical models. The authors measure product state-resolved translational energy spectra of photoproducts in a jet-cooled H2S beam as a function of wavelength, showing that SH yield is lower than assumed in the models.
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45
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Hendrix J, Bera PP, Lee TJ, Head-Gordon M. Cation, Anion, and Radical Isomers of C 4H 4N: Computational Characterization and Implications for Astrophysical and Planetary Environments. J Phys Chem A 2020; 124:2001-2013. [PMID: 32077700 DOI: 10.1021/acs.jpca.9b11305] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nitrogen-containing ions and molecules in the gas phase have been detected in non-Earth environments such as dark molecular clouds and more recently in the atmosphere of Saturn's moon Titan. These molecules may serve as precursors to larger heterocyclic structures that provide the foundation of complex biological molecules. On Titan, molecules of m/z 66 have been detected by the Cassini mission, and species of the empirical formula C4H4N may contribute to this signature. We have characterized seven isomers of C4H4N in anionic, neutral radical, and cationic states using density functional theory. Structures were optimized using the range-separated hybrid ωB97X-V with the cc-pVTZ and aug-cc-pVTZ basis sets. Anionic and radical C4H4N favor cyclic structures with aromatic and quasi-aromatic electron arrangements, respectively. Interestingly, ionization from the radical surface to the cation induces significant changes in structural stability, and the global minimum for positively charged isomers is CH2CCHCNH+, a pseudo-linear species reminiscent of cyanoallene. Select formation pathways to these structures from Titan's existing or postulated gas-phase species, reactions that are also relevant for other astrophysical environments, are discussed. By characterizing C4H4N isomers, we have identified energetically stable anionic, radical, and cationic structures that may be present in Titan's atmosphere and dark molecular clouds.
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Affiliation(s)
- Josie Hendrix
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Partha P Bera
- NASA Ames Research Center, Moffett Field, Mountain View, California 94035, United States.,Bay Area Environmental Research Institute, Moffett Field, Mountain View, California 94952, United States
| | - Timothy J Lee
- NASA Ames Research Center, Moffett Field, Mountain View, California 94035, United States
| | - Martin Head-Gordon
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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46
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Xie C, Zhao B, Malbon CL, Yarkony DR, Xie D, Guo H. Insights into the Mechanism of Nonadiabatic Photodissociation from Product Vibrational Distributions. The Remarkable Case of Phenol. J Phys Chem Lett 2020; 11:191-198. [PMID: 31821757 DOI: 10.1021/acs.jpclett.9b03407] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The fate of a photoexcited molecule is often strongly influenced by electronic degeneracies, such as conical intersections, which break the Born-Oppenheimer separation of electronic and nuclear motion. Detailed information concerning internal energy redistribution in a nonadiabatic process can be extracted from the product state distribution of a photofragment in photodissociation. Here, we focus on the nonadiabatic photodissociation of phenol and discuss the internal excitation of the phenoxyl fragment using both symmetry analysis and wave packet dynamics. It is shown that unique and general selection rules exist, which can be attributed to the geometric phase in the adiabatic representation. Further, our results provide a reinterpretation of the experimental data, shedding light on the impact of conical intersections on the product state distribution.
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Affiliation(s)
- Changjian Xie
- Institute of Modern Physics, Shaanxi Key Laboratory for Theoretical Physics Frontiers , Northwest University , Xian , Shaanxi 710127 , China
- Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Bin Zhao
- Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Christopher L Malbon
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - David R Yarkony
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Daiqian Xie
- Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , China
| | - Hua Guo
- Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
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47
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Henley A, Riley J, Wang B, Fielding HH. An experimental and computational study of the effect of aqueous solution on the multiphoton ionisation photoelectron spectrum of phenol. Faraday Discuss 2020; 221:202-218. [DOI: 10.1039/c9fd00079h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We revisit the photoelectron spectroscopy of aqueous phenol in an effort to improve our understanding of the impact of inhomogeneous broadening and inelastic scattering on solution-phase photoelectron spectra.
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Affiliation(s)
- Alice Henley
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
| | - Jamie W. Riley
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
| | - Bingxing Wang
- Department of Chemistry
- University College London
- London WC1H 0AJ
- UK
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48
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Crane SW, Ghafur O, Saalbach L, Paterson MJ, Townsend D. The influence of substituent position on the excited state dynamics operating in 4-, 5- and 6-hydroxyindole. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2019.136870] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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49
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Röder A, Skov AB, Boguslavskiy AE, Lausten R, Stolow A. VUV excited-state dynamics of cyclic ethers as a function of ring size. Phys Chem Chem Phys 2020; 22:26241-26254. [DOI: 10.1039/d0cp04292g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ultrafast vacuum ultraviolet (VUV) Rydberg state dynamics of cyclic ethers reflects ring strain.
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Affiliation(s)
- Anja Röder
- Department of Chemistry
- University of Ottawa
- Ottawa
- Canada
- University of Ottawa – National Research Council Joint Centre for Extreme Photonics
| | - Anders B. Skov
- Department of Chemistry
- University of Copenhagen
- 2100 København Ø
- Denmark
| | | | | | - Albert Stolow
- Department of Chemistry
- University of Ottawa
- Ottawa
- Canada
- Department of Physics
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50
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Biswas S, Bhattacharya I, Chakraborty T. Identification of an Emitting Metastable State of p-Fluorophenol-Ammonia 1:2 Complex by Laser-Induced Fluorescence Spectroscopy. J Phys Chem A 2019; 123:10563-10570. [PMID: 31714082 DOI: 10.1021/acs.jpca.9b07958] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have demonstrated here, for the first time to our knowledge, the formation of an emitting metastable species upon lowest electronic excitation (S1) of a hydrogen-bonded 1:2 complex of para-fluorophenol (pFP) with ammonia (NH3), which is known to be one of the smallest reactive complexes to undergo excited state H-atom transfer (HAT) reaction to produce •NH4(NH3) radical fragment. The emission spectrum of the species is characterized to be red-shifted, broad, and structureless. From the viewpoint of energy balance, an excited state proton transfer (ESPT) is unfavorable, but according to predicted electronic structure parameters, the metastable state species could be stabilized by charge transfer (CT) interaction at the hydrogen-bonded geometry of the complex. We propose that this species could act as an intermediate to the HAT process in the excited state. The observation of such a state could be valuable to understand the complex dynamics of similar events in biologically relevant systems.
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Affiliation(s)
- Souvick Biswas
- School of Chemical Sciences , Indian Association for the Cultivation of Science , 2A Raja S C Mullick Road, Jadavpur , Kolkata 700032 , India
| | - Indrani Bhattacharya
- School of Chemical Sciences , Indian Association for the Cultivation of Science , 2A Raja S C Mullick Road, Jadavpur , Kolkata 700032 , India
| | - Tapas Chakraborty
- School of Chemical Sciences , Indian Association for the Cultivation of Science , 2A Raja S C Mullick Road, Jadavpur , Kolkata 700032 , India
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