Possible molecular hydrogen formation mediated by the inner and outer carbon atoms of typical PAH cations
Possible molecular hydrogen formation mediated by the inner and outer carbon atoms of typical PAH cations
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DOI：
10.1016/j.chemphys.2004.07.010
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发表时间：
2004-10-25
期刊：
影响因子：
2.3
通讯作者：
Aihara, J
中科院分区：
文献类型：
--
作者：
Hirama, M;Tokosumi, T;Aihara, J
我们一直在研究气态多环芳烃（PAHs）自由基阳离子介导H-2形成的可能性。本研究在B3 LYP/6- 31 G ** 水平上对典型多环芳烃阳离子的外碳和内碳的催化作用进行了研究。我们推测H-2是通过两个基元反应形成的：一个H原子与PAH阳离子加成，另一个H原子从所得的芳烃离子中夺取H。结果发现，这两个反应进行没有或非常小的活化能。细化的活化能与自旋投影MP2程序证实了一个非常小的活化能的第二个反应。因此，PAH阳离子的至少一些碳原子在空间中提供了分子氢形成的位点。星际多环芳烃多为大而致密的多环芳烃，内部碳原子较多。因此，即使这样的碳原子可能不太容易受到H加成的影响，它们在星际化学中的催化作用也永远不会被忽视。(C)2004 Elsevier B. V.保留所有权利。
We have been studying the possibility of H-2 formation mediated by the radical cations of gaseous polycyclic aromatic hydrocarbons (PAHs). In this study, we explored the catalytic role of both outer and inner carbon atoms of some typical PAH cations at the B3LYP/6-31G** level of theory. We presumed that H-2 is formed by way of two elementary reactions: the addition of an H atom to a PAH cation and the H abstraction from the resulting arenium ion by another H atom. It was found that both reactions proceed with no or very small activation energies. Refinement of the activation energies with a spin-projected MP2 procedure confirmed a very small activation energy for the second reaction. It then follows that at least some carbon atoms of a PAH cation give sites for molecular hydrogen formation in space. Interstellar PAHs are mostly large compact ones with many inner carbon atoms. Therefore, even if such carbon atoms might be less susceptible to H addition, their catalytic role can never be overlooked in interstellar chemistry. (C) 2004 Elsevier B.V. All rights reserved.