Abstract

When exposed to a thermal beam of hydrogen atoms, gas-phase coronene cations C₂₄H₁₂⁺ can be sequentially hydrogenated. This process is accompanied by a gradual transition of the electronic structure from aromatic to aliphatic. The planar very stable coronene structure transforms into the significantly weaker corrugated structure, typical for aliphatic molecules. In this study, we have investigated the hydrogenation of 5 smaller polycyclic aromatic hydrocarbon cations using a combination of radiofrequency ion trapping with time-of-flight mass spectrometry. Anthracene (C₁₄H₁₀⁺), pyrene (C₁₆H₁₀⁺), triphenylene (C₁₈H₁₂⁺), tetracene (C₁₈H₁₂⁺) and 8-9-benzofluoranthene (C₂₀H₁₂⁺) only cover a small mass range, but differ in carbon/hydrogen ratio, number of outer-edge sites and overall structure. We have observed qualitatively similar initial hydrogenation patterns for all 5 molecular ions, with odd hydrogenation states being dominant. Strong quantitative differences in hydrogenation and in attachment-induced fragmentation were found. For the case of pyrene cations, we have also investigated exposure to atomic D. Clear lines of evidence for HD/D₂ abstraction reactions of Eley–Rideal type were found, as previously observed for coronene cations.

Graphical abstract

中文翻译：

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氢原子与小的多环芳烃阳离子的相互作用

摘要

当暴露于氢原子的热束中时，气相的gas烯阳离子C ₂₄ H ₁₂ ⁺可以被顺序地氢化。该过程伴随着电子结构从芳族到脂族的逐渐过渡。平面的非常稳定的co烯结构转变为明显较弱的波纹结构，这对于脂肪族分子而言是典型的。在这项研究中，我们研究了结合使用射频离子阱和飞行时间质谱仪对5种较小的多环芳烃阳离子的氢化反应。蒽（C ₁₄ H ₁₀ ⁺），pyr（C ₁₆ H ₁₀ ⁺），三亚苯基（C ₁₈ H₁₂ ⁺），并四苯（C ₁₈ H ₁₂ ⁺）和8-9-苯并荧蒽（C ₂₀ H ₁₂ ⁺）仅覆盖较小的质量范围，但碳/氢比，外边缘位点数量和整体结构不同。我们已经观察到所有5个分子离子的定性相似的初始氢化模式，其中奇数氢化态占主导。发现氢化和附着诱导的碎片存在强烈的定量差异。对于of阳离子，我们还研究了暴露于原子D的情况。发现了Eley–Rideal型HD / D ₂抽象反应的清晰证据，如先前对co烯阳离子所观察到的。

图形概要