Graduate School of Materials Science, Nara Institute of Science and Technology , 8916-5 Takayama-cho, Ikoma, Nara 630-0192, Japan.
Fujitsu Laboratories Ltd and Fujitsu Limited , 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0197, Japan.
ACS Nano. 2017 Jun 27;11(6):6204-6210. doi: 10.1021/acsnano.7b02316. Epub 2017 May 26.
Edge-fluorinated graphene nanoribbons are predicted to exhibit attractive structural and electronic properties, which, however, still need to be demonstrated experimentally. Hence, to provide further experimental insights, an anthracene trimer comprising a partially fluorinated central unit is explored as a precursor molecule, with scanning tunneling microscopy and X-ray photoelectron spectroscopy analyses, indicating the formation of partially edge-fluorinated polyanthrylenes via on-surface reactions after annealing at 350 °C on Au(111) under ultrahigh-vacuum conditions. Further annealing at 400 °C leads to the cyclodehydrogenation of partially edge-fluorinated polyanthrylenes to form graphene nanoribbons, resulting in carbon-fluorine bond cleavage despite its high dissociation energy. Extensive theoretical calculations reveal a defluorination-based reaction mechanism, showing that a critical intermediate structure, obtained as a result of H atom migration to the terminal carbon of a fluorinated anthracene unit in polyanthrylene, plays a crucial role in significantly lowering the activation energy of carbon-fluorine bond dissociation. These results suggest the importance of transient structures in intermediate states for synthesizing edge-fluorinated graphene nanoribbons.
边缘氟化石墨烯纳米带被预测具有吸引人的结构和电子性质，但仍需要通过实验来证明。因此，为了提供更多的实验见解，研究了一种包含部分氟化中心单元的蒽三聚物作为前体分子，通过扫描隧道显微镜和 X 射线光电子能谱分析，表明在 350°C 下在 Au(111)上退火时，通过表面反应形成了部分边缘氟化聚芳烃，在超高真空条件下。进一步在 400°C 退火导致部分边缘氟化聚芳烃的环脱氢形成石墨烯纳米带，尽管其离解能很高，但会导致碳-氟键断裂。广泛的理论计算揭示了基于脱氟的反应机制，表明关键的中间结构，是通过 H 原子迁移到聚芳烃中氟化蒽单元的末端碳上而获得的，对于显著降低碳-氟键离解的活化能起着至关重要的作用。这些结果表明，对于合成边缘氟化石墨烯纳米带，中间体中瞬态结构的重要性。
