Yang Xiaosheng, Egger Larissa, Hurdax Philipp, Kaser Hendrik, Lüftner Daniel, Bocquet François C, Koller Georg, Gottwald Alexander, Tegeder Petra, Richter Mathias, Ramsey Michael G, Puschnig Peter, Soubatch Serguei, Tautz F Stefan
Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425, Jülich, Germany.
Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425, Jülich, Germany.
Nat Commun. 2019 Jul 18;10(1):3189. doi: 10.1038/s41467-019-11133-9.
The determination of reaction pathways and the identification of reaction intermediates are key issues in chemistry. Surface reactions are particularly challenging, since many methods of analytical chemistry are inapplicable at surfaces. Recently, atomic force microscopy has been employed to identify surface reaction intermediates. While providing an excellent insight into the molecular backbone structure, atomic force microscopy is less conclusive about the molecular periphery, where adsorbates tend to react with the substrate. Here we show that photoemission tomography is extremely sensitive to the character of the frontier orbitals. Specifically, hydrogen abstraction at the molecular periphery is easily detected, and the precise nature of the reaction intermediates can be determined. This is illustrated with the thermally induced reaction of dibromo-bianthracene to graphene which is shown to proceed via a fully hydrogenated bisanthene intermediate. We anticipate that photoemission tomography will become a powerful companion to other techniques in the study of surface reaction pathways.
确定反应途径和识别反应中间体是化学中的关键问题。表面反应尤其具有挑战性，因为许多分析化学方法不适用于表面。最近，原子力显微镜已被用于识别表面反应中间体。虽然原子力显微镜能很好地洞察分子主链结构，但对于分子外围，吸附质往往会与底物发生反应的地方，它的结论性较差。在这里，我们表明光发射断层扫描对前沿轨道的特性极其敏感。具体而言，分子外围的氢提取很容易被检测到，并且可以确定反应中间体的确切性质。以二溴联蒽热诱导生成石墨烯的反应为例，该反应显示通过完全氢化的双蒽中间体进行。我们预计光发射断层扫描将成为研究表面反应途径的其他技术的有力辅助手段。
