On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons
作者机构：Present address:Istituto di Struttura della Materia-CNR(ISM-CNR)via Fosso del Cavaliere 10000133RomaItaly Present address:IMDEA NanoscienceC/Faraday 9Campus de Cantoblanco28049MadridSpain Max Planck Institute for Polymer Research55128MainzGermany EmpaSwiss Federal Laboratories for Materials Science and Technologynanotech@surfaces Laboratory8600DübendorfSwitzerland Organic and Carbon Nanomaterials UnitOkinawa Institute of Science and Technology Graduate University1919-1 TanchaOnna-sonKunigami-gunOkinawa904-0495Japan Institute of Physical ChemistryJohannes Gutenberg University MainzDuesbergweg 10-1455128MainzGermany
出 版 物：《Nano Research》 (纳米研究（英文版）)
年 卷 期：2021年第14卷第12期
页 面：4754-4759页
核心收录：
学科分类：07[理学] 070205[理学-凝聚态物理] 08[工学] 080501[工学-材料物理与化学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学]
基 金：We are grateful for the financial support by the Max Planck Society,the Swiss National Science Foundation under Grant No.200020_182015 the NCCR MARVEL funded by the Swiss National Science Foundation(No.51NF40-182892) the European Union’s Horizon 2020 research and innovation programme under grant agreement number 785219(Graphene Flagship Core 2) the Office of Naval Research(No.N00014-18-1-2708) the Okinawa Institute of Science and Technology Graduate University(OIST) The Swiss National Supercomputing Centre(CSCS)under project ID s904 is acknowledged for computational resources
主 题：graphene nanoribbons on-surface synthesis scanning-tunneling microscope noncontact atomic force microscope C-H activation
摘 要：Graphene nanoribbons (GNRs) have potential for applications in electronic devices. A key issue, thereby, is the fine-tuning of their electronic characteristics, which can be achieved through subtle structural modifications. These are not limited to the conventional armchair, zigzag, and cove edges, but also possible through incorporation of non-hexagonal rings. On-surface synthesis enables the fabrication and visualization of GNRs with atomically precise chemical structures, but strategies for the incorporation of non-hexagonal rings have been underexplored. Herein, we describe the on-surface synthesis of armchair-edged GNRs with incorporated five-membered rings through the C-H activation and cyclization of benzylic methyl groups. Ortho-Tolyl-substituted dibromobianthryl was employed as the precursor monomer, and visualization of the resulting structures after annealing at 300 °C on a gold surface by high-resolution noncontact atomic force microscopy clearly revealed the formation of methylene-bridged pentagons at the GNR edges. These persisted after annealing at 340 °C, along with a few fully conjugated pentagons having singly-hydrogenated apexes. The benzylic methyl groups could also migrate or cleave-off, resulting in defects lacking the five-membered rings. Moreover, unexpected and unique structural rearrangements, including the formation of embedded heptagons, were observed. Despite the coexistence of different reaction pathways that hamper selective synthesis of a uniform structure, our results provide novel insights into on-surface reactions en route to functional, non-benzenoid carbon nanomaterials.
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