Zghida Khaldia, Hamza Reguig Farouk, Alcamí Manuel, Mokhtar Lamsabhi Al
LCPM Laboratory, Faculty of Exact and Applied Sciences, Chemistry Department, University of Oran, 1 Ahmed BenBella, Oran, 31000, Algeria.
Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Madrid, 28049, Spain.
Chemphyschem. 2025 Mar 15;26(6):e202400729. doi: 10.1002/cphc.202400729. Epub 2024 Dec 29.
In this study, we systematically explored the stability and isomerism of neutral and dehydrogenated polycyclic aromatic hydrocarbons (PAHs) in various charge states, focusing on anthracene, acridine, and phenazine. Our findings highlight key aspects that deepen the understanding of these molecules' reactivity and stability, relevant in both laboratory and astrophysical contexts. Structural symmetry and the presence of nitrogen atoms significantly impact PAH stability and reactivity. The optimal site for the first dehydrogenation varies with charge state, with notable differences in stability observed across different positions and charge states. For the loss of two hydrogens, there is a clear competition between low and high spin states, influenced by the positions of the hydrogens lost. Infrared spectral analysis reveals characteristic frequencies of conjugated C-C bonds and variations across different charge states. The elimination of H typically occurs at adjacent carbons, forming bonds similar to triple bonds. Reaction networks for anthracene, acridine, and phenazine indicate preferred pathways for hydrogen loss, driven by the need to minimize charge repulsion and maintain aromaticity. Adjacent hydrogen loss is predominant in neutral and singly charged states, shifting to non-adjacent loss in higher charge states.
在本研究中，我们系统地探究了处于各种电荷状态的中性和脱氢多环芳烃（PAHs）的稳定性和异构现象，重点关注蒽、吖啶和吩嗪。我们的研究结果突出了一些关键方面，这些方面加深了对这些分子在实验室和天体物理环境中的反应性和稳定性的理解。结构对称性和氮原子的存在显著影响PAH的稳定性和反应性。首次脱氢的最佳位点随电荷状态而变化，在不同位置和电荷状态下观察到稳定性存在显著差异。对于失去两个氢的情况，低自旋态和高自旋态之间存在明显竞争，这受到失去氢的位置的影响。红外光谱分析揭示了共轭C-C键的特征频率以及不同电荷状态下的变化。H的消除通常发生在相邻碳原子处，形成类似于三键的键。蒽、吖啶和吩嗪的反应网络表明了氢损失的优先途径，这是由最小化电荷排斥和保持芳香性的需要驱动的。在中性和单电荷状态下，相邻氢损失占主导，在更高电荷状态下则转变为非相邻氢损失。
