Identification of the fragment of the 1-methylpyrene cation by mid-IR spectroscopy

TL;DR

This study uses mid-IR spectroscopy and theoretical calculations to identify the specific isomeric form of the 1-methylpyrene cation, revealing insights into its structure and behavior under experimental conditions.

Contribution

The paper demonstrates the identification of the PyrCH2+ isomer of the 1-methylpyrene cation using combined IR spectroscopy and density functional theory, highlighting isomerization effects.

Findings

Identification of PyrCH2+ as the isomeric form in experiments

Observation of anharmonicity and isomerization effects during heating

Correlation between experimental spectra and theoretical predictions

Abstract

The fragment of the 1-methylpyrene cation, C17H11+, is expected to exist in two isomeric forms, 1-pyrenemethylium PyrCH2+ and the tropylium containing species PyrC7+ . We measured the infrared (IR) action spectrum of cold C17H11+ tagged with Ne using a cryogenic ion trap instrument coupled to the FELIX laser. Comparison of the experimental data with density functional theory calculations allows us to identify the PyrCH2+ isomer in our experiments. The IR Multi-Photon Dissociation spectrum was also recorded following the C2H2 loss channel. Its analysis suggests combined effects of anharmonicity and isomerisation while heating the trapped ions, as shown by molecular dynamics simulations.