Adsorption of Helium and Hydrogen on Triphenylene and 1,3,5-Triphenylbenzene

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Authors

Bergmeister Bergmeister, University of Innsbruck
Kollotzek Kollotzek, University of Innsbruck
Florent Calvo, Université Grenoble Alpes
Elisabeth Gruber, University of Innsbruck
Fabio Zappa, University of Innsbruck
Paul Scheier, University of Innsbruck
Olof E. Echt, olof.echt@unh.eduFollow

Abstract

The adsorption of helium or hydrogen on cationic triphenylene (TPL, C₁₈H₁₂), a planar polycyclic aromatic hydrocarbon (PAH) molecule, and of helium on cationic 1,3,5-triphenylbenzene (TPB, C₂₄H₁₈), a propeller-shaped PAH, is studied by a combination of high-resolution mass spectrometry and classical and quantum computational methods. Mass spectra indicate that He_nTPL⁺ complexes are particularly stable if n = 2 or 6, in good agreement with the quantum calculations which show that for these sizes the helium atoms are strongly localized on either side of the central carbon ring for n = 2 and on either side of the three outer rings for n = 6. Theory suggests that He₁₄TPL⁺ is also particularly stable, with the helium atoms strongly localized on either side of the central and outer rings plus the vacancies between the outer rings. For He_nTPB⁺ the mass spectra hint at enhanced stability for n = 2, 4 and, possibly, 11. Here the agreement with theory is less satisfactory, probably because TPB⁺ is a highly fluxional molecule. In the global energy minimum, the phenyl groups are rotated in the same direction but when the zero-point harmonic correction is included, a structure with one phenyl group being rotated opposite to the other two becomes lower in energy. The energy barrier between the two isomers is very small, and TPB⁺ could be in a mixture of symmetric and antisymmetric states, or possibly even vibrationally delocalized.

Department

Physics

Publication Date

8-22-2022

Journal Title

Molecules

Language

English

Publisher

MDPI AG, Basel

Digital Object Identifier (DOI)

https://dx.doi.org/10.3390/molecules27154937

Document Type

Article

Recommended Citation

S. Bergmeister, S. Kollotzek, F. Calvo, E. Gruber, F. Zappa, P. Scheier, O. Echt, Molecules 27 (2022) 4937

Rights

© 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Comments

This article belongs to the Special Issue Noble Gas Compounds and Chemistry II

This is an Open Access article published by MDPI in Molecules in 2022, available online: https://doi.org/10.3390/molecules27154937