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Abyar F, Novak I. Investigation on the electronic structures of thiamine and related compounds: Free base or salt? J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.113988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Valadbeigi Y, Causon T. Significance of Competitive Reactions in an Atmospheric Pressure Chemical Ionization Ion Source: Effect of Solvent. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:961-973. [PMID: 35562191 PMCID: PMC9164235 DOI: 10.1021/jasms.2c00034] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 05/02/2022] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
Ionization of organic compounds with different structural and energetic properties including benzene derivatives, polycyclic aromatic hydrocarbons (PAHs), ketones, and polyenes was studied using a commercial atmospheric pressure corona discharge (APCI) ion source on a drift tube ion mobility-quadrupole-time-of-flight mass spectrometer (IM-QTOFMS). It was found that the studied cohort of compounds can be experimentally ionized via protonation, charge transfer, and hydride abstraction leading to formation of [M + H]+, [M]+•, and [M - H]+ species, respectively. By experimentally monitoring the product ions and comparing the thermodynamic data for different ionization paths, it was proposed that NO+ is one of the main reactant ions (RIs) in the ion source used. Of particular focus in this work were theoretical and experimental studies of the effect of solvents frequently used for analytical applications with this ion source (acetonitrile, methanol, and chloroform) on the ionization mechanisms. In methanol, the studied compounds were observed to be ionized mainly via proton transfer while acetonitrile suppressed the protonation of compounds and enhanced their ionization via charge transfer and hydride abstraction. Use of chloroform as a solvent led to formation of CHCl2+ as an alternative reactant ion (RI) to ionize the analytes via electrophilic substitution. Density functional theory (DFT) was used to study the different paths of ionization. The theoretical and experimental results showed that by using only the absolute thermodynamic data, the real ionization path cannot be determined and the energies of all competing processes such as charge transfer, protonation, and hydride abstraction need to be compared.
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Majer K, Signorell R, Heringa MF, Goldmann M, Hemberger P, Bodi A. Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast. Chemistry 2019; 25:14192-14204. [PMID: 31469456 DOI: 10.1002/chem.201903282] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Indexed: 11/06/2022]
Abstract
The photoionization of thymine has been studied by using vacuum ultraviolet radiation and imaging photoelectron photoion coincidence spectroscopy after aerosol flash vaporization and bulk evaporation. The two evaporation techniques have been evaluated by comparison of the photoelectron spectra and breakdown diagrams. The adiabatic ionization energies for the first four electronic states were determined to be 8.922±0.008, 9.851±0.008, 10.30±0.02, and 10.82±0.01 eV. Vibrational features have been assigned for the first three electronic states with the help of Franck-Condon factor calculations based on density functional theory and wave function theory vibrational analysis within the harmonic approximation. The breakdown diagram of thymine, as supported by composite method ab initio calculations, suggests that the main fragment ions are formed in sequential HNCO-, CO-, and H-loss dissociation steps from the thymine parent ion, with the first step corresponding to a retro-Diels-Alder reaction. The dissociation rate constants were extracted from the photoion time-of-flight distributions and used together with the breakdown curves to construct a statistical model to determine 0 K appearance energies of 11.15±0.16 and 11.95±0.09 eV for the m/z 83 and 55 fragment ions, respectively. These results have allowed us to revise previously proposed fragmentation mechanisms and to propose a model for the final, nonstatistical H-loss step in the breakdown diagram, yielding the m/z 54 fragment ion at an appearance energy of 13.24 eV.
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Affiliation(s)
- Katharina Majer
- Paul Scherrer Institute, 5232, Villigen, Switzerland.,Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, 8093, Zürich, Switzerland
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, 8093, Zürich, Switzerland
| | - Maarten F Heringa
- Paul Scherrer Institute, 5232, Villigen, Switzerland.,Present address: Givaudan Schweiz AG, 8310, Kemptthal, Switzerland
| | - Maximilian Goldmann
- Gymnasium Lerbermatt, 3098, Köniz, Switzerland.,Hochschule Luzern - Technik & Architektur, 6048, Horw, Switzerland
| | | | - Andras Bodi
- Paul Scherrer Institute, 5232, Villigen, Switzerland
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Heringa MF, Slowik JG, Goldmann M, Signorell R, Hemberger P, Bodi A. The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid. Chemphyschem 2017; 18:3595-3604. [PMID: 28987011 DOI: 10.1002/cphc.201700983] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 09/30/2017] [Indexed: 11/10/2022]
Abstract
The valence threshold photoionization of oleic acid has been studied using synchrotron VUV radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. An oleic acid aerosol beam was impacted on a copper thermodesorber, heated to 130 °C, to evaporate the particles quantitatively. Upon threshold photoionization, oleic acid produces the intact parent ion first, followed by dehydration at higher energies. Starting at ca. 10 eV, a large number of fragment ions slowly rise suggesting several fragmentation coordinates with quasi-degenerate activation energies. However, water loss is the dominant low-energy dissociation channel, and it is shown to be closely related to the unsaturated carbon chain. In the lowest-barrier process, one of the four allylic hydrogen atoms is transferred to the carboxyl group to form the leaving water molecule and a cyclic ketone fragment ion. A statistical model to analyze the breakdown diagram and measured rate constants yields a 0 K appearance energy of 9.77 eV, which can be compared with the density functional theory result of 9.19 eV. Alternative H-transfer steps yielding a terminal C=O group are ruled out based on energetics and kinetics arguments. Some of the previous photoionization mass spectrometric studies also reported 2 amu and 26 amu loss fragment ions, corresponding to hydrogen and acetylene loss. We could not identify such peaks in the mass spectrum of oleic acid.
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Affiliation(s)
- Maarten F Heringa
- Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232, Villigen PSI, Switzerland.,Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232, Villigen PSI, Switzerland
| | - Jay G Slowik
- Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232, Villigen PSI, Switzerland
| | - Maximilian Goldmann
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232, Villigen PSI, Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, 5232, Villigen PSI, Switzerland
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Mairhofer L, Eibenberger S, Cotter JP, Romirer M, Shayeghi A, Arndt M. Quantum-Assisted Metrology of Neutral Vitamins in the Gas Phase. Angew Chem Int Ed Engl 2017; 56:10947-10951. [PMID: 28599088 PMCID: PMC5582605 DOI: 10.1002/anie.201704916] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Indexed: 11/11/2022]
Abstract
It has recently been shown that matter-wave interferometry can be used to imprint a periodic nanostructure onto a molecular beam, which provides a highly sensitive tool for beam displacement measurements. Herein, we used this feature to measure electronic properties of provitamin A, vitamin E, and vitamin K1 in the gas phase for the first time. The shift of the matter-wave fringes in a static electric field encodes the molecular susceptibility and the time-averaged dynamic electric dipole moment. The dependence of the fringe pattern on the intensity of the central light-wave diffraction grating was used to determine the molecular optical polarizability. Comparison of our experimental findings with molecular dynamics simulations and density functional theory provides a rich picture of the electronic structures and dynamics of these biomolecules in the gas phase with β-carotene as a particularly interesting example.
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Affiliation(s)
- Lukas Mairhofer
- Faculty of Physics, VCQUniversity of ViennaBoltzmanngasse 51090ViennaAustria
| | - Sandra Eibenberger
- Faculty of Physics, VCQUniversity of ViennaBoltzmanngasse 51090ViennaAustria
- Lyman LaboratoryHarvard UniversityDepartment of Physics17 Oxford StreetCambridgeMA02138USA
| | - Joseph P. Cotter
- Faculty of Physics, VCQUniversity of ViennaBoltzmanngasse 51090ViennaAustria
- Centre for cold matterBlackett LaboratoryImperial CollegePrince Consort RoadLondonSW7 2BWUK
| | - Marion Romirer
- Faculty of Physics, VCQUniversity of ViennaBoltzmanngasse 51090ViennaAustria
| | - Armin Shayeghi
- Faculty of Physics, VCQUniversity of ViennaBoltzmanngasse 51090ViennaAustria
| | - Markus Arndt
- Faculty of Physics, VCQUniversity of ViennaBoltzmanngasse 51090ViennaAustria
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Mairhofer L, Eibenberger S, Cotter JP, Romirer M, Shayeghi A, Arndt M. Quanteninterferenzexperimente für die Vermessung von Vitaminen in der Gasphase. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201704916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Lukas Mairhofer
- Fakultät für Physik, VCQ; Universität Wien; Boltzmanngasse 5 1090 Wien Österreich
| | - Sandra Eibenberger
- Fakultät für Physik, VCQ; Universität Wien; Boltzmanngasse 5 1090 Wien Österreich
- Lyman Laboratory; Harvard University; Department of Physics; 17 Oxford Street Cambridge MA 02138 USA
| | - Joseph P. Cotter
- Fakultät für Physik, VCQ; Universität Wien; Boltzmanngasse 5 1090 Wien Österreich
- Centre for cold matter; Blackett Laboratory; Imperial College; Prince Consort Road London SW7 2BW Großbritannien
| | - Marion Romirer
- Fakultät für Physik, VCQ; Universität Wien; Boltzmanngasse 5 1090 Wien Österreich
| | - Armin Shayeghi
- Fakultät für Physik, VCQ; Universität Wien; Boltzmanngasse 5 1090 Wien Österreich
| | - Markus Arndt
- Fakultät für Physik, VCQ; Universität Wien; Boltzmanngasse 5 1090 Wien Österreich
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Abyar F, Farrokhpour H. Ionization of vitamin B6 in the gas phase and water: Theoretical study. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2016.12.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Abyar F, Farrokhpour H. Ionization of vitamin C in gas phase: Theoretical study. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2016; 160:11-7. [PMID: 27092998 DOI: 10.1016/j.jphotobiol.2016.03.057] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 03/26/2016] [Accepted: 03/29/2016] [Indexed: 11/27/2022]
Abstract
In this work, the gas phase ionization energies and photoelectron spectra of four important conformers of vitamin C were calculated. Symmetry adapted cluster/configuration interaction methodology employing the single and double excitation operators (SAC-CI SD-R) along with D95++(d,p) basis set were used for the calculations. Thermochemistry calculations were also performed on all possible conformers of vitamin C to find the relative stability of conformers in the gas phase. The calculated ionization bands of each conformer were assigned by calculating the contribution of natural bonding orbital (NBO) in the calculated canonical molecular orbitals involved in the ionization. SAC-CI calculations showed that the first ionization band of vitamin C is related to the π electrons of CC bond of the ring of molecule although, there is the lone electron pairs of oxygen atoms and π electrons of CO bond in the molecule.
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Affiliation(s)
- Fatemeh Abyar
- Department of Engineering, Ardakan University, Ardakan 89518-95491, Iran.
| | - Hossein Farrokhpour
- Chemistry Department, Isfahan University of Technology, Isfahan 84156-83111, Iran.
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