共价键合芴团簇的实验室光化学：有趣的PAH碗形成机制的观察
Laboratory photo-chemistry of covalently bonded fluorene clusters: observation of an interesting PAH bowl-forming mechanism
摘要：
富勒烯C $_{60}$是星际介质（ISM）中发现的最大的分子之一，已经提出通过大的（超过60个C原子）多环芳烃（PAH）分子的光化学处理自上而下形成。在这篇文章中，我们专注于相反的过程，调查富勒烯形成的可能性，从小的多环芳烃，其中碗形成起着核心作用。我们结合实验室实验和量子化学计算来研究带电芴团簇形成较大的多环芳烃。实验表明，在可见激光照射下，芴二聚体阳离子- [C $_{13}$ H $_{9}$ $-$ C $_{13}$ H $_{9}$ ] $^+$ -和芴三聚体阳离子- [C $_{13}$ H $_{8}$ $-$ C $_{13}$ H $_{9}$ ] $^+$ -发生光脱氢和光异构化，产生碗状结构的芳香簇离子，C $_{26}$ H $_{12}$ $^+$和C $_{39}$ H $_{20}$ $^+$。为了研究这个化学过程的细节，我们采用量子化学，使我们能够确定新形成的簇离子的结构，计算氢损失解离能，并推导出潜在的反应途径。这些结果表明，较小的多环芳烃簇（小于60个碳原子）可以转化为较大的碗状几何结构，可能作为富勒烯的构建块，因为碗形成机制大大促进了从脱氢多环芳烃到笼的转化。此外，碗状的形成诱导了一个永久的偶极矩，原则上允许使用射电天文学来寻找这样的物种。
英文摘要：
The fullerene C$_{60}$, one of the largest molecules identified in the interstellar medium (ISM), has been proposed to form top-down through the photo-chemical processing of large (more than 60 C-atoms) polycyclic aromatic hydrocarbon (PAH) molecules. In this article, we focus on the opposite process, investigating the possibility that fullerenes form from small PAHs, in which bowl-forming plays a central role. We combine laboratory experiments and quantum chemical calculations to study the formation of larger PAHs from charged fluorene clusters. The experiments show that with visible laser irradiation, the fluorene dimer cation - [C$_{13}$H$_{9}$$-$C$_{13}$H$_{9}$]$^+$ - and the fluorene trimer cation - [C$_{13}$H$_{9}$$-$C$_{13}$H$_{8}$$-$C$_{13}$H$_{9}$]$^+$ - undergo photo-dehydrogenation and photo-isomerization resulting in bowl structured aromatic cluster-ions, C$_{26}$H$_{12}$$^+$ and C$_{39}$H$_{20}$$^+$, respectively. To study the details of this chemical process, we employ quantum chemistry that allows us to determine the structures of the newly formed cluster-ions, to calculate the hydrogen loss dissociation energies, and to derive the underlying reaction pathways. These results demonstrate that smaller PAH clusters (with less than 60 C-atoms) can convert to larger bowled geometries that might act as building blocks for fullerenes, as the bowl-forming mechanism greatly facilitates the conversion from dehydrogenated PAHs to cages. Moreover, the bowl-forming induces a permanent dipole moment that - in principle - allows to search for such species using radio astronomy.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
