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On-Surface Synthesis of Anthracene-Fused Zigzag Graphene Nanoribbons from 2,7-Dibromo-9,9′-bianthryl Reveals Unexpected Ring Rearrangements

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Precision Chemistry 2024年第2期2卷 81-87页

作者： Xiushang Xu Amogh Kinikar Marco Di Giovannantonio Carlo A.Pignedoli Pascal Ruffieux Klaus Müllen roman fasel Akimitsu Narita Max Planck Institute for Polymer Research 55128 MainzGermany Organic and Carbon Nanomaterials Unit Okinawa Institute of Science and Technology Graduate UniversityKunigami-gunOkinawa 904-0495Japan Empa Swiss Federal Laboratories for Materials Science and Technologynanotech@surfaces Laboratory8600 DübendorfSwitzerland Institute of Structure of Matter-CNR(ISM-CNR) 00133 RomaItaly Institute of Physical Chemistry Johannes Gutenberg University Mainz55128 MainzGermany Department of Chemistry Biochemistry and Pharmaceutical SciencesUniversity of Bern3012 BernSwitzerland

On-surface synthesis has emerged as a powerful strategy to fabricate unprecedented forms of atomically precise graphene nanoribbons(GNRs).However,the on-surface synthesis of zigzag GNRs(ZGNR)has met with only limited ***,we report the synthesis and on-surface reactions of 2,7-dibromo-9,9′-bianthryl as the precursor towardπ-extended *** by scanning tunneling microscopy and high-resolution noncontact atomic force microscopy clearly demonstrated the formation of anthracene-fused *** skeletal rearrangements were also observed,which could be explained by intramolecular Diels-Alder *** calculations of the electronic properties of the anthracene-fused ZGNRs revealed spin-polarized edge-states and a narrow bandgap of 0.20 eV.

关键词： On-surface synthesis Graphene nanoribbon On-surface reaction Rearrangement Edge state

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Molecular heterostructure by fusing graphene nanoribbons of different lengths through a pentagon ring junction

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Nano Research 2022年第9期15卷 8465-8469页

作者： Qiang Sun Hao Jiang Yuyi Yan roman fasel Pascal Ruffieux Materials Genome Institute Shanghai UniversityShanghai 200444China Empa Swiss Federal Laboratories for Materials Science and TechnologyDübendorf 8600Switzerland Department of Chemistry Biochemistry and Pharmaceutical SciencesUniversity of BernBern 3012Switzerland

Graphene nanoribbons(GNRs)have attracted great research interest because of their widely tunable and unique electronic *** required atomic precision of GNRs can be realized via on-surface synthesis *** this work,through a surface assisted reaction we have longitudinally fused the pyrene-based graphene nanoribbons(pGNR)of different lengths by a pentagon ring junction,and built a molecular junction structure on Au(111).The electronic properties of the structure are studied by scanning tunneling spectroscopy(STS)combined with tight binding(TB)*** pentagon ring junction shows a weak electronic coupling effect on graphene nanoribbons,which makes the electronic properties of the two different graphene nanoribbons connected by a pentagon ring junction analogous to type I semiconductor heterojunctions.

关键词： graphene nanoribbons(GNRs) scanning tunneling spectroscopy(STS) non-contact atomic force microscopy(nc-AFM) tight-binding(TB)calculations junction structure

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On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

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Nano Research 2021年第12期14卷 4754-4759页

作者： Xiushang Xu Marco Di Giovannantonio José I.Urgel Carlo A.Pignedoli Pascal Ruffieux Klaus Müllen roman fasel Akimitsu Narita Present address:Istituto di Struttura della Materia-CNR(ISM-CNR) via Fosso del Cavaliere 10000133RomaItaly Present address:IMDEA Nanoscience C/Faraday 9Campus de Cantoblanco28049MadridSpain Max Planck Institute for Polymer Research 55128MainzGermany Empa Swiss Federal Laboratories for Materials Science and Technologynanotech@surfaces Laboratory8600DübendorfSwitzerland Organic and Carbon Nanomaterials Unit Okinawa Institute of Science and Technology Graduate University1919-1 TanchaOnna-sonKunigami-gunOkinawa904-0495Japan Institute of Physical Chemistry Johannes Gutenberg University MainzDuesbergweg 10-1455128MainzGermany

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.

关键词： graphene nanoribbons on-surface synthesis scanning-tunneling microscope noncontact atomic force microscope C-H activation

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