1
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Molina FL, Broquier M, Soorkia S, Grégoire G, Pino GA. Selective Tautomer Production and Cryogenic Ion Spectroscopy of Radical Cations: The Uracil and Thymine Cases. J Phys Chem A 2024. [PMID: 38656804 DOI: 10.1021/acs.jpca.4c02199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The vibrational and electronic spectroscopy of the radical cations of two nucleobases (NB) (uracil and thymine) was studied by cryogenic ion photodissociation spectroscopy. The radical cations have been generated from the photodissociation of NB-Ag+ complexes. A charge transfer process from the NB to Ag+ governs the deactivation mechanism, leading to the formation of the radical cation without further tautomerization. Single- and double-resonance spectroscopy allows for structural assignments of both the silver complexes and the radical cations by comparison with DFT-based calculations. Interestingly, a tautomer-dependent fragmentation is observed in the thymine enol form that involves the loss of NCO, a fragment which was never reported before for this NB. This selective photodissociation of silver complexes containing aromatic chromophore greatly expands the current technique to produce isomer-selected radical cations in the gas phase providing benchmark experimental data to assess calculations of open-shell species.
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Affiliation(s)
- Franco L Molina
- Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba. Haya de la Torre y Medina Allende. Pabellón Argentina, Ciudad Universitaria, Córdoba X5000HUA, Argentina
- INFIQC: Instituto de Investigaciones en Físico-Química de Córdoba (CONICET-UNC). Haya de la Torre y Medina Allende. Pabellón Argentina, Ciudad Universitaria, Córdoba X5000HUA, Argentina
- Departamento de Fisicoquímica, Fac. de Ciencias Químicas, Universidad Nacional de Córdoba. Haya de la Torre y Medina Allende. Pabellón Argentina, Ciudad Universitaria, Córdoba X5000HUA, Argentina
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay F-91405, France
| | - Michel Broquier
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay F-91405, France
| | - Satchin Soorkia
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay F-91405, France
| | - Gilles Grégoire
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay F-91405, France
| | - Gustavo A Pino
- Centro Láser de Ciencias Moleculares, Universidad Nacional de Córdoba. Haya de la Torre y Medina Allende. Pabellón Argentina, Ciudad Universitaria, Córdoba X5000HUA, Argentina
- INFIQC: Instituto de Investigaciones en Físico-Química de Córdoba (CONICET-UNC). Haya de la Torre y Medina Allende. Pabellón Argentina, Ciudad Universitaria, Córdoba X5000HUA, Argentina
- Departamento de Fisicoquímica, Fac. de Ciencias Químicas, Universidad Nacional de Córdoba. Haya de la Torre y Medina Allende. Pabellón Argentina, Ciudad Universitaria, Córdoba X5000HUA, Argentina
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2
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Lowe B, Cardona AL, Bodi A, Mayer PM, Burgos Paci MA. The Unimolecular Chemistry of Methyl Chloroformate Ions and Neutrals: A Story of Near-Threshold Decomposition. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:2831-2839. [PMID: 38008918 DOI: 10.1021/jasms.3c00334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2023]
Abstract
The near-threshold dissociation of ionized and neutral methyl chloroformate (CH3COOCl, MCF) was explored with imaging photoelectron photoion coincidence spectroscopy. The threshold photoelectron spectrum (TPES) for MCF was acquired for the first time; the large geometry changes upon ionization of MCF result in a broad, poorly defined TPES. Franck-Condon simulations are consistent with an adiabatic ionization energy (IE) of 10.90 ± 0.05 eV. Ionized MCF dissociates by chlorine atom loss at a measured 0 K appearance energy (AE) of 11.30 ± 0.01 eV. Together with the above IE, this AE suggests a reaction barrier of 0.40 ± 0.05 eV, consistent with the SVECV-f12 computational result of 0.41 eV. At higher internal energies, the loss of CH3O• becomes competitive due to its lower entropy of activation. Pyrolysis of neutral MCF formed the anticipated major products CH3Cl + CO2 (R1) and the minor products HCl + CO + CH2O (R2). The thermal decomposition products were identified by their photoion mass-selected threshold photoelectron spectrum (ms-TPES). Possible reaction pathways were explored computationally to confirm the dominant ones: R1 proceeds by a concerted Cl atom migration via a four-membered transition state in agreement with the mechanism proposed in the literature. R2 is a two-step reaction first yielding 2-oxiranone by HCl loss, which then decomposes to CH2O and CO. Kinetic modeling of the neutral decomposition could simulate the observed reactions only if the vibrational temperature of the MCF was assumed not to cool in the expansion.
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Affiliation(s)
- Bethany Lowe
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Alejandro L Cardona
- INFIQC - CONICET, Departamento fisicoquímica, Universidad Nacional de Córdoba, Córdoba, Argentina X5000HUA
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Paul M Mayer
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Canada K1N 6N5
| | - Maxi A Burgos Paci
- INFIQC - CONICET, Departamento fisicoquímica, Universidad Nacional de Córdoba, Córdoba, Argentina X5000HUA
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3
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Asmussen JD, Abid AR, Sundaralingam A, Bastian B, Sishodia K, De S, Ben Ltaief L, Krishnan S, Pedersen HB, Mudrich M. Secondary ionization of pyrimidine nucleobases and their microhydrated derivatives in helium nanodroplets. Phys Chem Chem Phys 2023; 25:24819-24828. [PMID: 37671772 DOI: 10.1039/d3cp02879h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Radiation damage in biological systems by ionizing radiation is predominantly caused by secondary processes such as charge and energy transfer leading to the breaking of bonds in DNA. Here, we study the fragmentation of cytosine (Cyt) and thymine (Thy) molecules, clusters and microhydrated derivatives induced by direct and indirect ionization initiated by extreme-ultraviolet (XUV) irradiation. Photofragmentation mass spectra and photoelectron spectra of free Cyt and Thy molecules are compared with mass and electron spectra of Cyt/Thy clusters and microhydrated Cyt/Thy molecules formed by aggregation in superfluid helium (He) nanodroplets. Penning ionization after resonant excitation of the He droplets is generally found to cause less fragmentation compared to direct photoionization and charge-transfer ionization after photoionization of the He droplets. When Cyt/Thy molecules and oligomers are complexed with water molecules, their fragmentation is efficiently suppressed. However, a similar suppression of fragmentation is observed when homogeneous Cyt/Thy clusters are formed in He nanodroplets, indicating a general trend. Penning ionization electron spectra (PIES) of Cyt/Thy are broad and nearly featureless but PIES of their microhydrated derivatives point at a sequential ionization process ending in unfragmented microsolvated Cyt/Thy cations.
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Affiliation(s)
- Jakob D Asmussen
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
| | - Abdul R Abid
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
| | | | - Björn Bastian
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
| | - Keshav Sishodia
- Quantum Center of Excellence for Diamond and Emergent Materials and Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Subhendu De
- Quantum Center of Excellence for Diamond and Emergent Materials and Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Ltaief Ben Ltaief
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
| | - Sivarama Krishnan
- Quantum Center of Excellence for Diamond and Emergent Materials and Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Henrik B Pedersen
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
| | - Marcel Mudrich
- Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
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4
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Wang S, Dauletyarov Y, Krüger P, Horke DA. High-throughput UV-photofragmentation studies of thymine and guanine. Phys Chem Chem Phys 2023; 25:12322-12330. [PMID: 37083208 PMCID: PMC10155487 DOI: 10.1039/d3cp00328k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Abstract
High-throughput photofragmentation studies of thymine and guanine were performed at 257 and 343 nm and for a wide range of ionisation laser intensities. Combining a continuous laser-based thermal desorption source with femtosecond multiphoton ionisation using a 50 kHz repetition rate laser allowed us to produce detailed 2D maps of fragmentation as a function of incident laser intensity. The fragmentation was distinctly soft, the parent ions being at least an order of magnitude more abundant than fragment ions. For thymine there was a single dominant fragmentation channel, which involves consecutive HNCO and CO losses. In contrast, for guanine there were several competing ones, the most probable channel corresponding to CH2N2 loss through opening of the pyrimidine ring. The dependence of parent ion abundance on the ionisation laser intensity showed that at 257 nm the ionisation of thymine is a 1 + 1 resonance enhanced process through its open-shell singlet state.
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Affiliation(s)
- Siwen Wang
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
| | - Yerbolat Dauletyarov
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
| | - Peter Krüger
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
| | - Daniel A Horke
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
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5
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Hartweg S, Hochlaf M, Garcia GA, Nahon L. Photoionization Dynamics and Proton Transfer within the Adenine-Thymine Nucleobase Pair. J Phys Chem Lett 2023; 14:3698-3705. [PMID: 37040591 DOI: 10.1021/acs.jpclett.3c00564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Studying the stability of hydrogen-bonded nucleobase pairs, at the heart of the genetic code, is of utmost importance for an in-depth understanding of basic mechanisms of life and biomolecular evolution. We present here a VUV single photon ionization dynamic study of the nucleobase pair adenine-thymine (AT), revealing its ionization and dissociative ionization thresholds via double imaging electron/ion coincidence spectroscopy. The experimental data, consisting of cluster mass-resolved threshold photoelectron spectra and photon energy-dependent ion kinetic energy release distributions, allow the unambiguous distinction of the dissociation of AT into protonated adenine AH+ and a dehydrogenated thymine radical T(-H) from dissociative ionization processes of other nucleobase clusters. Comparison to high-level ab initio calculations indicates that our experimental observations can be explained by a single hydrogen-bonded conformer present in our molecular beam and allows the estimation of an upper limit of the barrier of the proton transfer in the ionized AT pair.
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Affiliation(s)
- Sebastian Hartweg
- Synchrotron Soleil, L'Orme des Merisiers, Départementale 128, 91190 St Aubin, France
- University of Freiburg, Institute of Physics, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
| | - Majdi Hochlaf
- Université Gustave Eiffel, COSYS/IMSE, 5 Bd Descartes, 77454 Champs sur Marne, France
| | - Gustavo A Garcia
- Synchrotron Soleil, L'Orme des Merisiers, Départementale 128, 91190 St Aubin, France
| | - Laurent Nahon
- Synchrotron Soleil, L'Orme des Merisiers, Départementale 128, 91190 St Aubin, France
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6
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Ultrafast Photo-Ion Probing of the Relaxation Dynamics in 2-Thiouracil. Molecules 2023; 28:molecules28052354. [PMID: 36903604 PMCID: PMC10005304 DOI: 10.3390/molecules28052354] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 02/19/2023] [Accepted: 02/20/2023] [Indexed: 03/08/2023] Open
Abstract
In this work, we investigate the relaxation processes of 2-thiouracil after UV photoexcitation to the S2 state through the use of ultrafast, single-colour, pump-probe UV/UV spectroscopy. We place focus on investigating the appearance and subsequent decay signals of ionized fragments. We complement this with VUV-induced dissociative photoionisation studies collected at a synchrotron, allowing us to better understand and assign the ionisation channels involved in the appearance of the fragments. We find that all fragments appear when single photons with energy > 11 eV are used in the VUV experiments and hence appear through 3+ photon-order processes when 266 nm light is used. We also observe three major decays for the fragment ions: a sub-autocorrelation decay (i.e., sub-370 fs), a secondary ultrafast decay on the order of 300-400 fs, and a long decay on the order of 220 to 400 ps (all fragment dependent). These decays agree well with the previously established S2 → S1 → Triplet → Ground decay process. Results from the VUV study also suggest that some of the fragments may be created by dynamics occurring in the excited cationic state.
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7
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Miura Y, Yamamoto YI, Karashima S, Orimo N, Hara A, Fukuoka K, Ishiyama T, Suzuki T. Formation of Long-Lived Dark States during Electronic Relaxation of Pyrimidine Nucleobases Studied Using Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy. J Am Chem Soc 2023; 145:3369-3381. [PMID: 36724068 DOI: 10.1021/jacs.2c09803] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Ultrafast electronic relaxation of nucleobases from 1ππ* states to the ground state (S0) is considered essential for the photostability of DNA. However, transient absorption spectroscopy (TAS) has indicated that some nucleobases in aqueous solutions create long-lived 1nπ*/3ππ* dark states from the 1ππ* states with a high quantum yield of 0.4-0.5. We investigated electronic relaxation in pyrimidine nucleobases in both aqueous solutions and the gas phase using extreme ultraviolet (EUV) time-resolved photoelectron spectroscopy. Femtosecond EUV probe pulses cause ionization from all electronic states involved in the relaxation process, providing a clear overview of the electronic dynamics. The 1nπ* quantum yields for aqueous cytidine and uracil (Ura) derivatives were found to be considerably lower (<0.07) than previous estimates reported by TAS. On the other hand, aqueous thymine (Thy) and thymidine exhibited a longer 1ππ* lifetime and a higher quantum yield (0.12-0.22) for the 1nπ* state. A similar trend was found for isolated Thy and Ura in the gas phase: the 1ππ* lifetimes are 39 and 17 fs and the quantum yield for 1nπ* are 1.0 and 0.45 for Thy and Ura, respectively. The result indicates that single methylation to the C5 position hinders the out-of-plane deformation that drives the system to the conical intersection region between 1ππ* and S0, providing a large impact on the photophysics/photochemistry of a pyrimidine nucleobase. The significant reduction of 1nπ* yield in aqueous solution is ascribed to the destabilization of the 1nπ* state induced by hydrogen bonding.
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Affiliation(s)
- Yuta Miura
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Yo-Ichi Yamamoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Shutaro Karashima
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Natsumi Orimo
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Ayano Hara
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Kanae Fukuoka
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
| | - Tatsuya Ishiyama
- Department of Applied Chemistry, Graduate School of Science and Engineering, University of Toyama, Toyama930-8555, Japan
| | - Toshinori Suzuki
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto606-8502, Japan
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8
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Zinck N, Bodi A, Mayer PM. VUV photoprocessing of oxygen-containing polycyclic aromatic hydrocarbons: iPEPICO study of the unimolecular dissociation of ionized benzofuran. CAN J CHEM 2022. [DOI: 10.1139/cjc-2022-0062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) are potential contributors to the 11.3 m band in interstellar observations. To further explore their role in the interstellar medium, we have investigated their fate after photoprocessing by VUV radiation; in particular, we studied the dissociative photoionization of the simplest OPAH, benzofuran, with imaging photoelectron photoion coincidence spectroscopy, iPEPICO. Ionized benzofuran dissociates by loss of CO, followed by a sequential H atom loss. The parallel HCO-loss channel, leading to the same bicyclic C7H5+ fragment ion, is not competitive at low excess energies above the ionization threshold. However, the collision-induced dissociation tandem mass spectrometry results suggest that CO and HCO may be formed in parallel at higher energies. An RRKM fragmentation model reproduced the iPEPICO data well assuming the initial 1,2-H shift transition state to be rate determining to CO loss. The breakdown diagram and the measured dissociation rates agreed well at the CBS-QB3-calculated activation energy of 2.99 eV, which could be relaxed to 3.25 eV, and only a slight adjustment of the ab initio activation entropy. The model barrier to sequential H-loss is larger than the computed H-loss threshold and the breakdown diagram rises less steeply than predicted, which indicates suprastatistical kinetic energy release after the tight H-transfer transition state of the first step. HCO cleavage is possible after a ring-opening transition state, which is looser than and isoenergetic with the CO-loss transition state. However, a subsequent ring formation transition state at 3.85 eV is moderately tight, which suppresses HCO loss at low excess energies.
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Affiliation(s)
- Nicholas Zinck
- University of Ottawa, 6363, Chemistry and Biomolecular Sciences, Ottawa, Ontario, Canada
| | - Andras Bodi
- Paul Scherrer Institut PSI, 28498, Laboratory for Synchrotron Radiation and Femtochemistry, Villigen, Aargau, Switzerland
| | - Paul M Mayer
- University of Ottawa, 6363, Chemistry and Biomolecular Sciences, Ottawa, Ontario, Canada,
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9
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Giustini A, Winfough M, Czekner J, Sztáray B, Meloni G, Bodi A. Photoionization of Two Potential Biofuel Additives: γ-Valerolactone and Methyl Butyrate. J Phys Chem A 2021; 125:10711-10724. [PMID: 34918933 DOI: 10.1021/acs.jpca.1c08033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The photoionization of two potential biofuel additives, γ-valerolactone (GVL, C5H8O2) and methyl butyrate (MB, C5H10O2) has been studied by imaging photoelectron photoion coincidence spectroscopy (iPEPICO) at the VUV beamline of the Swiss Light Source (SLS). The vibrational fine structure in the photoelectron spectrum is compared with a Franck-Condon simulation for the electronic ground-state band of the GVL cation. In the lowest energy dissociative photoionization channel of GVL, CO2 is lost, resulting in a 1-butene fragment ion with a 0 K appearance energy of E0 = 10.35 ± 0.01 eV. A newly calculated 1-butene ionization energy of 9.595 ± 0.015 eV establishes the reverse barrier height to CO2 loss as 66.6 ± 4.3 kJ mol-1. Methyl butyrate cations undergo McLafferty rearrangement, which explains the missing ion signal at the computed adiabatic ionization energy of 9.25 eV. After H transfer, ethylene is lost in the lowest energy dissociation channel to yield the methyl acetate enol ion at E0 = 10.24 ± 0.04 eV. This value connects the energetics of methyl butyrate with that of methyl acetate enol ion, which is established at ΔfHo0K[CH2C(OH)OCH3+] = 502 ± 6 kJ mol-1. Parallel to ethylene loss, methyl loss is also observed from the enol tautomer of the parent ion. Both samples exhibit low-energy nonstatistical dissociative ionization channels. In GVL, the methyl-loss abundance rises quickly but levels off suddenly in the energy range of the first electronically excited states, indicating nonstatistical competition between CH3 and CO2 loss. In MB, the major parallel dissociation channel is the loss of a methoxy radical. Calculations indicate that McLafferty rearrangement is inhibited on the excited-state surface. Indeed, breakdown curve modeling of this and a sequential CO-loss channel confirms a second statistical regime in dissociative photoionization, decoupled from ethylene loss.
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Affiliation(s)
- Andrea Giustini
- Dipartimento di Scienze Fisiche e Chimiche, University of L'Aquila, 67100 L'Aquila, Italy
| | - Matthew Winfough
- Department of Chemistry, University of San Francisco, 2130 Fulton Street, San Francisco, California 94117-1080, United States
| | - Joseph Czekner
- Institut für Physikalische Chemie II, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany
| | - Bálint Sztáray
- Department of Chemistry, University of the Pacific, 3601 Pacific Avenue, Stockton, California 95211, United States
| | - Giovanni Meloni
- Dipartimento di Scienze Fisiche e Chimiche, University of L'Aquila, 67100 L'Aquila, Italy.,Department of Chemistry, University of San Francisco, 2130 Fulton Street, San Francisco, California 94117-1080, United States
| | - Andras Bodi
- Laboratory for Femtochemistry and Synchrotron Radiation, Paul Scherrer Institut (PSI), 5232 Villigen, Switzerland
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10
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Robinson MS, Niebuhr M, Lever F, Mayer D, Metje J, Gühr M. Ultrafast Photo-ion Probing of the Ring-Opening Process in Trans-Stilbene Oxide. Chemistry 2021; 27:11418-11427. [PMID: 34037274 PMCID: PMC8453962 DOI: 10.1002/chem.202101343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Indexed: 11/25/2022]
Abstract
The ultrafast photo‐induced ring opening of the oxirane derivative trans‐stilbene oxide has been studied through the use of ultrafast UV/UV pump‐probe spectroscopy by using photo‐ion detection. Single‐ and multiphoton probe paths and final states were identified through comparisons between UV power studies and synchrotron‐based vacuum ultraviolet (VUV) single‐photon ionization studies. Three major time‐dependent features of the parent ion (sub‐450 fs decay, (1.5±0.2) ps, and >100 ps) were observed. These decays are discussed in conjunction with the primary ring‐opening mechanism of stilbene oxide, which occurs through C−C dissociation in the oxirane ring. The appearance of fragments relating to the masses of dehydrogenated diphenylmethane (167 amu) and dehydrogenated methylbenzene (90 amu) were also investigated. The appearance of the 167 amu fragment could suggest an alternative ultrafast ring‐opening pathway via the dissociation of one of the C−O bonds within the oxirane ring.
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Affiliation(s)
- Matthew S Robinson
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam-Golm, Germany.,Centre for Free Electron Lasers (CFEL) DESY, Notkestraße 85, 22607, Hamburg, Germany
| | - Mario Niebuhr
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam-Golm, Germany
| | - Fabiano Lever
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam-Golm, Germany
| | - Dennis Mayer
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam-Golm, Germany
| | - Jan Metje
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam-Golm, Germany
| | - Markus Gühr
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476, Potsdam-Golm, Germany
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11
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Borges R, Colby SM, Das S, Edison AS, Fiehn O, Kind T, Lee J, Merrill AT, Merz KM, Metz TO, Nunez JR, Tantillo DJ, Wang LP, Wang S, Renslow RS. Quantum Chemistry Calculations for Metabolomics. Chem Rev 2021; 121:5633-5670. [PMID: 33979149 PMCID: PMC8161423 DOI: 10.1021/acs.chemrev.0c00901] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Indexed: 02/07/2023]
Abstract
A primary goal of metabolomics studies is to fully characterize the small-molecule composition of complex biological and environmental samples. However, despite advances in analytical technologies over the past two decades, the majority of small molecules in complex samples are not readily identifiable due to the immense structural and chemical diversity present within the metabolome. Current gold-standard identification methods rely on reference libraries built using authentic chemical materials ("standards"), which are not available for most molecules. Computational quantum chemistry methods, which can be used to calculate chemical properties that are then measured by analytical platforms, offer an alternative route for building reference libraries, i.e., in silico libraries for "standards-free" identification. In this review, we cover the major roadblocks currently facing metabolomics and discuss applications where quantum chemistry calculations offer a solution. Several successful examples for nuclear magnetic resonance spectroscopy, ion mobility spectrometry, infrared spectroscopy, and mass spectrometry methods are reviewed. Finally, we consider current best practices, sources of error, and provide an outlook for quantum chemistry calculations in metabolomics studies. We expect this review will inspire researchers in the field of small-molecule identification to accelerate adoption of in silico methods for generation of reference libraries and to add quantum chemistry calculations as another tool at their disposal to characterize complex samples.
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Affiliation(s)
- Ricardo
M. Borges
- Walter
Mors Institute of Research on Natural Products, Federal University of Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
| | - Sean M. Colby
- Biological
Science Division, Pacific Northwest National
Laboratory, Richland, Washington 99352, United States
| | - Susanta Das
- Department
of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Arthur S. Edison
- Departments
of Genetics and Biochemistry and Molecular Biology, Complex Carbohydrate
Research Center and Institute of Bioinformatics, University of Georgia, Athens, Georgia 30602, United States
| | - Oliver Fiehn
- West
Coast Metabolomics Center for Compound Identification, UC Davis Genome
Center, University of California, Davis, California 95616, United States
| | - Tobias Kind
- West
Coast Metabolomics Center for Compound Identification, UC Davis Genome
Center, University of California, Davis, California 95616, United States
| | - Jesi Lee
- West
Coast Metabolomics Center for Compound Identification, UC Davis Genome
Center, University of California, Davis, California 95616, United States
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Amy T. Merrill
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Kenneth M. Merz
- Department
of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Thomas O. Metz
- Biological
Science Division, Pacific Northwest National
Laboratory, Richland, Washington 99352, United States
| | - Jamie R. Nunez
- Biological
Science Division, Pacific Northwest National
Laboratory, Richland, Washington 99352, United States
| | - Dean J. Tantillo
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Lee-Ping Wang
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Shunyang Wang
- West
Coast Metabolomics Center for Compound Identification, UC Davis Genome
Center, University of California, Davis, California 95616, United States
- Department
of Chemistry, University of California, Davis, California 95616, United States
| | - Ryan S. Renslow
- Biological
Science Division, Pacific Northwest National
Laboratory, Richland, Washington 99352, United States
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12
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Wu X, Zhou X, Bjelić S, Hemberger P, Bodi A. Valence Photoionization and Energetics of Vanillin, a Sustainable Feedstock Candidate. J Phys Chem A 2021; 125:3327-3340. [PMID: 33872037 DOI: 10.1021/acs.jpca.1c00876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We studied the valence photoionization of vanillin by photoelectron photoion coincidence spectroscopy in the 8.20-19.80 eV photon energy range. Vertical ionization energies by EOM-IP-CCSD calculations reproduce the photoelectron spectral features. Composite method calculations and Franck-Condon simulation of the weak, ground-state band yield the adiabatic ionization energy of the most stable vanillin conformer as 8.306(20) eV. The lowest energy dissociative photoionization channels correspond to hydrogen atom, carbon monoxide, and methyl losses, which form the dominant C8H7O3+ (m/z 151) and the less intense C7H8O2+ (m/z 124) and C7H5O3+ (m/z 137) fragment ions in parallel dissociation channels at modeled 0 K appearance energies of 10.13(1), 10.40(3), and 10.58(10) eV, respectively. On the basis of the breakdown diagram, we explore the energetics of sequential methyl and carbon monoxide loss channels, which dominate the fragmentation mechanism at higher photon energies. The 0 K appearance energy for sequential CO loss from the m/z 151 fragment to C7H7O2+ (m/z 123) is 12.99(10) eV, and for sequential CH3 loss from the m/z 123 fragment to C6H4O2+ (m/z 108), it is 15.40(20) eV based on the model. Finally, we review the thermochemistry of the bi- and trifunctionalized benzene derivatives guaiacol, hydroxybenzaldehyde, anisaldehyde, and vanillin. On the basis of isodesmic functional group exchange reactions, we propose new enthalpies of formations, among them ΔfH°298K(vanillin, g) = -383.5 ± 2.9 kJ mol-1. These mechanistic insights and ab initio thermochemistry results will support analytical works to study lignin conversion involving vanillin.
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Affiliation(s)
- Xiangkun Wu
- Paul Scherrer Institute, 5232 Villigen, Switzerland.,Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Saša Bjelić
- Paul Scherrer Institute, 5232 Villigen, Switzerland
| | | | - Andras Bodi
- Paul Scherrer Institute, 5232 Villigen, Switzerland
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13
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Wu X, Zhou X, Hemberger P, Bodi A. Dissociative Photoionization of Chloro-, Bromo-, and Iodocyclohexane: Thermochemistry and the Weak C–Br Bond in the Cation. J Phys Chem A 2021; 125:646-656. [DOI: 10.1021/acs.jpca.0c10386] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xiangkun Wu
- Paul Scherrer Institute, Villigen 5232, Switzerland
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | | | - Andras Bodi
- Paul Scherrer Institute, Villigen 5232, Switzerland
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14
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Wu X, Zhou X, Hemberger P, Bodi A. Conformers, electronic states, and diabolical conical intersections in the valence photoelectron spectroscopy of halocyclohexanes. J Chem Phys 2020; 153:054305. [DOI: 10.1063/5.0018293] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Xiangkun Wu
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland
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15
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Wu X, Zhou X, Hemberger P, Bodi A. A guinea pig for conformer selectivity and mechanistic insights into dissociative ionization by photoelectron photoion coincidence: fluorocyclohexane. Phys Chem Chem Phys 2020; 22:2351-2360. [PMID: 31934711 DOI: 10.1039/c9cp05617c] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We studied fluorocyclohexane (C6H11F, FC6) by double imaging photoelectron photoion coincidence spectroscopy in the 9.90-13.90 eV photon energy range. The photoelectron spectrum can identify species isomer and, in this case, even conformer selectively. Ab initio results indicated that the axial conformer has two, close-lying cation electronic states. With the help of Franck-Condon simulations of the vibrational fine structure, we determined the origin of three transitions, (i) axial FC6 → axial FC6+ of C1 symmetry (X[combining tilde]+, A'' in CS), (ii) equatorial FC6 → equatorial FC6+ of C1 symmetry (X[combining tilde]+, A'' in CS), and (iii) axial FC6 → A' axial FC6+ of CS symmetry (Ã+) as 10.12 ± 0.01, 10.15 ± 0.01 and 10.15 ± 0.02 eV, respectively. At slightly higher energies, the FC6 cation starts fragmenting by HF loss (E0 = 10.60 eV), followed by sequential CH3 (E0 = 10.71 eV) or C2H4 (E0 = 11.06 eV) loss. Surprisingly, the methyl-loss step has an effective barrier of only 0.11 eV, and yet it is a slow process at threshold. Based on the statistical model, this is explained by isomerization and stabilization of the C6H10+ intermediate. The highest energy channel observed, vinyl fluoride (C2H3F) loss yielding C4H8+ appears in the breakdown diagram at 12 eV, which agrees with the computed threshold to cyclobutane cation formation. However, the model predicted a ca. 1 eV competitive shift for this parallel channel, i.e., an E0 = 11.23 eV. This led us to explore the potential energy surface to find a lower-lying fragmentation channel including H-transfer steps. Rate constant measurements and statistical modeling thus yield fundamental insights into the reaction mechanism beyond what is immediately seen in the mass spectra.
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Affiliation(s)
- Xiangkun Wu
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland. and Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
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16
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Hemberger P, van Bokhoven JA, Pérez-Ramírez J, Bodi A. New analytical tools for advanced mechanistic studies in catalysis: photoionization and photoelectron photoion coincidence spectroscopy. Catal Sci Technol 2020. [DOI: 10.1039/c9cy02587a] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
How can we detect reactive and elusive intermediates in catalysis to unveil reaction mechanisms? In this mini review, we discuss novel photoionization tools to support this quest.
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Affiliation(s)
- Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry
- Paul Scherrer Institute
- CH-5232 Villigen PSI
- Switzerland
| | - Jeroen A. van Bokhoven
- Laboratory for Catalysis and Sustainable Chemistry
- Paul Scherrer Institute
- CH-5232 Villigen PSI
- Switzerland
- Institute for Chemical and Bioengineering
| | - Javier Pérez-Ramírez
- Institute for Chemical and Bioengineering
- Department of Chemistry and Applied Biosciences
- ETH Zurich
- Zurich
- Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry
- Paul Scherrer Institute
- CH-5232 Villigen PSI
- Switzerland
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