Xiushang Xu^1,2, Marco Di Giovannantonio³, José I. Urgel³, Carlo A. Pignedoli^3*, Pascal Ruffieux³, Klaus Müllen^1,4, Roman Fasel^3*, Akimitsu Narita^1,2

1 Max Planck Institute for Polymer Research, 55128, Mainz, Germany

2 Organic and Carbon Nanomaterials Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan

3 Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland

4 Institute of Physical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany

* Corresponding authors emails: carlo.pignedoli@empa.ch, roman.fasel@empa.ch

DOI10.24435/materialscloud:yc-k5 [version v1]

Publication date: Oct 26, 2021

How to cite this record

Xiushang Xu, Marco Di Giovannantonio, José I. Urgel, Carlo A. Pignedoli, Pascal Ruffieux, Klaus Müllen, Roman Fasel, Akimitsu Narita, On-surface activation of benzylic C–H bonds for the synthesis of pentagon-fused graphene nanoribbons, Materials Cloud Archive 2021.169 (2021), doi: 10.24435/materialscloud:yc-k5.

Description

In this record we provide data to support our recent findings related to the fabrication of pentagon-fused graphene nanoribbons. 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. In the publication, 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.

Materials Cloud sections using this data

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Keywords

graphene nanoribbons on surface synthesis ab initio MARVEL/DD3 CSCS SNSF