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Rossi C, Muller G, Thissen R, Romanzin C, Alcaraz C, Gondarry S, Mayer PM, Jacovella U. New light on the imbroglio surrounding the C 8H +6 isomers formed from ionized azulene and naphthalene using ion-molecule reactions. Chem Sci 2023; 15:317-327. [PMID: 38131094 PMCID: PMC10731908 DOI: 10.1039/d3sc03015f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 11/14/2023] [Indexed: 12/23/2023] Open
Abstract
Most polycyclic aromatic hydrocarbons (PAHs) can isomerize with internal energies near to or below the dissociation threshold. The C10H+8 group of ions, made up of the naphthalene (Naph+) and the azulene (Azu+) radical cations, is a prototypical example. C8H+6 isomers are important species in the growth kinetics and formation of complex organic molecules, and more generally fragments from larger PAHs, yet information about C8H+6 structures is scarce and contradictory. Here, ion-molecule reactions were carried out and the tunable photoionization chemical monitoring technique was used to probe the C8H+6 isomers formed upon C2H2-loss from Naph+ and Azu+. The experimental findings were interpreted with the support of ab initio and kinetics calculations. To facilitate the interpretation of these data, chemical reactivity starting from phenylacetylene (PA) was studied. It was found that most of the C8H+6 ions formed from C10H8, in a timescale of 40 μs, are PA+ in the vicinity of the dissociation threshold. No evidence of the pentalene radical cation (PE+) was observed and explanations to reconcile previous results are presented.
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Affiliation(s)
- Corentin Rossi
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay 91405 Orsay France
| | - Giel Muller
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong Wollongong New South Wales 2522 Australia
| | - Roland Thissen
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000 91405 Orsay France
- Synchrotron SOLEIL L'Orme des Merisiers, 91192 Saint Aubin, Gif-sur-Yvette France
| | - Claire Romanzin
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000 91405 Orsay France
- Synchrotron SOLEIL L'Orme des Merisiers, 91192 Saint Aubin, Gif-sur-Yvette France
| | - Christian Alcaraz
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000 91405 Orsay France
- Synchrotron SOLEIL L'Orme des Merisiers, 91192 Saint Aubin, Gif-sur-Yvette France
| | - Sandesh Gondarry
- Department of Chemistry and Biomolecular Sciences, University of Ottawa Ottawa K1N 6N5 Canada
| | - Paul M Mayer
- Department of Chemistry and Biomolecular Sciences, University of Ottawa Ottawa K1N 6N5 Canada
| | - Ugo Jacovella
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay 91405 Orsay France
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Kamer J, Schleier D, Donker M, Hemberger P, Bodi A, Bouwman J. Threshold photoelectron spectroscopy and dissociative photoionization of benzonitrile. Phys Chem Chem Phys 2023; 25:29070-29079. [PMID: 37861750 DOI: 10.1039/d3cp03977c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
The threshold photoionization and dissociative ionization of benzonitrile (C6H5CN) were studied using double imaging photoelectron photoion coincidence (i2PEPICO) spectroscopy at the Vacuum Ultraviolet (VUV) beamline of the Swiss Light Source (SLS). The threshold photoelectron spectrum was recorded from 9.6 to 12.7 eV and Franck-Condon simulations of ionization into the ionic ground state, X̃+, as well as the B̃+ and C̃+ states were performed to assign the observed vibronic structures. The adiabatic ionization energies of the X̃+, B̃+ and C̃+ states are determined to be (9.72 ± 0.02), (11.85 ± 0.03) and, tentatively, (12.07 ± 0.04) eV, respectively. Threshold ionization mass spectra were recorded from 13.75 to 19.75 eV and the breakdown diagram was constructed by plotting the fractional abundances of the parent ion and ionic dissociation products as a function of photon energy. The seven lowest energy dissociative photoionization channels of benzonitrile were found to yield CN˙ + c-C6H5+, HCN + C6H4˙+, C2H4 + HC5N˙+, HC3N + C4H4˙+, H2C3N˙ + C4H3+, CH2CHCN + C4H2˙+ and H2C4N˙ + c-C3H3+. HCN loss from the benzonitrile cation is the dominant dissociation channel from the dissociation onset of up to 18.1 eV and CH2CHCN loss becomes dominant from 18.1 eV and up. We present extensive potential energy surface calculations on the C6H5CN˙+ surface to rationalize the detected products. The breakdown diagram and time-of-flight mass spectra are fitted using a Rice-Ramsperger-Kassel-Marcus statistical model. Anchoring the fit to the CBS-QB3 result (3.42 eV) for the barrier to HCN loss, we obtained experimental dissociation barriers for the products of 4.30 eV (CN loss), 5.53 eV (C2H4 loss), 4.33 eV (HC3N loss), 5.15 eV (H2C3N loss), 4.93 eV (CH2CHCN loss) and 4.41 eV (H2C4N loss). We compare our work to studies of the electron-induced dissociative ionization of benzonitrile and isoelectronic phenylacetylene (C8H6), as well as the VUV-induced dissociation of protonated benzonitrile (C6H5CNH+). Also, we discuss the potential role of barrierless association reactions found for some of the identified fragments as a source of benzonitrile(˙+) in interstellar chemistry and in Titan's atmosphere.
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Affiliation(s)
- Jerry Kamer
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
| | - Domenik Schleier
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
- Lehrstuhl Technische Thermodynamik, Fakultät für Maschinenbau, Universität Paderborn, Warburger Str. 100, 33098 Paderborn, Germany
| | - Merel Donker
- Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - Jordy Bouwman
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA.
- Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
- Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT), NASA/SSERVI, Boulder, CO 80309, USA
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Jacovella U, Rossi C, Romanzin C, Alcaraz C, Thissen R. Monitoring the Light-induced Isomerisation of the Prototypical Polycyclic Aromatic Hydrocarbons C 10 H 8 + through Ion-Molecule Reactions. Chemphyschem 2023; 24:e202200474. [PMID: 36125423 PMCID: PMC10092717 DOI: 10.1002/cphc.202200474] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 09/20/2022] [Indexed: 01/20/2023]
Abstract
Structural rearrangements in ions are essential for understanding the composition and evolution of energetic and chemically active environments. This study explores the interconversion routes for simple polycyclic aromatic hydrocarbons, namely naphthalene and azulene radical cations (C10 H8 + ), by combining mass spectrometry and vacuum ultraviolet tunable synchrotron radiation through the chemical monitoring technique. Products of ion-molecule reactions are used to probe C10 H8 + structures that are formed as a function of their internal energies. Isomerisation from azulene radical cation towards naphthalene radical cation in a timescale faster than 80 μs was monitored, whereas no reverse isomerisation was observed in the same time window. When energising C10 H8 + with more than 6 eV, the reactivity of C10 H8 + unveils the formation of a new isomeric group with a contrasted reactivity compared with naphthalene and azulene cations. We tentatively assigned these structures to phenylvinylacetylene cations.
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Affiliation(s)
- Ugo Jacovella
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France
| | - Corentin Rossi
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000, 91405, Orsay, France
| | - Claire Romanzin
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000, 91405, Orsay, France.,Synchrotron SOLEIL, L'Orme des Merisiers, 91192, Saint Aubin, Gif-sur-Yvette, France
| | - Christian Alcaraz
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000, 91405, Orsay, France.,Synchrotron SOLEIL, L'Orme des Merisiers, 91192, Saint Aubin, Gif-sur-Yvette, France
| | - Roland Thissen
- Université Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000, 91405, Orsay, France.,Synchrotron SOLEIL, L'Orme des Merisiers, 91192, Saint Aubin, Gif-sur-Yvette, France
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