IR spectra of cationic 1,5,9-triazacoronene and two of its cationic derivatives

Jerry Kamer; Domenik Schleier; Andy Jiao; Grégory Schneider; Jonathan Martens; Giel Berden; Jos Oomens; Jordy Bouwman

doi:10.1039/d4cp03004d

IR spectra of cationic 1,5,9-triazacoronene and two of its cationic derivatives

Phys Chem Chem Phys. 2024 Nov 13;26(44):27912-27921. doi: 10.1039/d4cp03004d.

Authors

Jerry Kamer¹, Domenik Schleier^{1

2}, Andy Jiao³, Grégory Schneider³, Jonathan Martens⁴, Giel Berden⁴, Jos Oomens⁴, Jordy Bouwman^{5

6

7}

Affiliations

¹ Laboratory for Astrophysics, Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands.
² Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, Berlin 10623, Germany.
³ Leiden Institute of Chemistry, Leiden University, 2300 RA Leiden, The Netherlands.
⁴ Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
⁵ Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA. jordy.bouwman@colorado.edu.
⁶ Department of Chemistry, University of Colorado, Boulder, CO 80309, USA.
⁷ Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT), NASA/SSERVI, Boulder, CO 80309, USA.

PMID: 39495341
DOI: 10.1039/d4cp03004d

Abstract

Infrared emission features are observed towards diverse astronomical objects in the interstellar medium (ISM). Generally, the consensus is that these IR features originate from polycyclic aromatic hydrocarbons (PAHs) and are hence named aromatic infrared bands (AIBs). More recently, it has been suggested that nitrogen substituted PAHs (PANHs) contribute to the AIBs as well and it has even been shown that nitrogen inclusion in PAHs can improve the match with the AIBs, specifically around the 6.2 μm feature. In order to determine which specific molecules or functional groups are at the origin of the AIBs, IR spectra of various PA(N)Hs are experimentally and computationally studied. In this work we expand on the spectroscopic investigation of PANHs by presenting the gas-phase mid-IR spectra of 1,5,9-triazacoronene˙⁺ (TAC˙⁺, m/z 303), a threefold nitrogenated congener of coronene˙⁺, its protonated derivative TACH⁺ (m/z 304) and the product that forms when water adds to dehydrogenated TAC˙⁺[TAC-H + H₂O]⁺ (m/z 320). We analyze the mid-IR spectra by comparing them with vibrational modes calculated at the B3LYP/6-311++G(d,p) level a theory and we present a possible geometry for [TAC-H + H₂O]⁺. The TAC˙⁺ mid-IR spectrum is compared to that of coronene˙⁺ and is demonstrated to be remarkably similar. We put TAC˙⁺ and TACH⁺ into astronomical context by comparing their recorded mid-IR spectra to observed ISM spectra of four spectral classes. From this we conclude that TAC˙⁺ and TACH⁺ could both contribute to the AIBs, with TACH⁺ being a more likely contributor than TAC˙⁺.