On-Surface Synthesis of Oligo(indenoindene)

Giovannantonio, Marco Di; Chen, Qiang; Urgel, José I.; Ruffieux, Pascal; Pignedoli, Carlo A.; Müllen, Kläus; Narita, Akimitsu; Fasel, Román

doi:10.1021/jacs.0c05701

Cited by 34 publications

(35 citation statements)

References 39 publications

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“…9 To the best of our knowledge, paraconnected TAM polymers were only experimentally studied several decades ago in one single study, 29 although recently the electronic structure of other types of Kekulé 1D oligomers has been assessed by different in-solution and on-surface spectroscopies. 30,31 In all these cases a complete, or partial, multi-radical character was found, which is in agreement with the higher degree of aromatization in the open-shell conguration, making it generally more stable than the fully paired quinoidal distribution. 21 Therefore, it is not very clear how the quinoidal conguration could be stabilized in such type of para-connected TAM polymers, or what is the effect of chemical functionalization on the resulting electronic conguration, as opposed to TAM bi-radicals where this has been extensively studied in the past.…”

Section: Introductionsupporting

confidence: 73%

Conformational control over π-conjugated electron pairing in 1D organic polymers

et al. 2021

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Section: Introductionsupporting

confidence: 73%

Conformational control over π-conjugated electron pairing in 1D organic polymers

et al. 2021

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“…For instance, the nature of the electronic ground state of long pursued members of the acene [14][15][16][17][18][19] and triangulene [20,21] families, widely discussed in theoretical studies, have only recently been untangled. Contemporarily, a successful strategy toward the on-surface formation of open-shell NGs, one-dimensional polymers and graphene nanoribbons (GNRs) is the surface-assisted oxidative ring closure between a methyl group and the neighboring aryl moiety of a properly predesigned molecular precursor, which occurs after thermal activation [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Such synthetic approach, though often successful, presents some limitations related to the cleavage of methyl groups prior to cyclization, which may lead to the formation of topological defects inducing an open-shell ground state to NGs [30,37].…”

Section: Introductionmentioning

confidence: 99%

Defect-Induced π-Magnetism into Non-Benzenoid Nanographenes

Biswas

Yang

et al. 2022

Nanomaterials

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The synthesis of nanographenes (NGs) with open-shell ground states have recently attained increasing attention in view of their interesting physicochemical properties and great prospects in manifold applications as suitable materials within the rising field of carbon-based magnetism. A potential route to induce magnetism in NGs is the introduction of structural defects, for instance non-benzenoid rings, in their honeycomb lattice. Here, we report the on-surface synthesis of three open-shell non-benzenoid NGs (A1, A2 and A3) on the Au(111) surface. A1 and A2 contain two five- and one seven-membered rings within their benzenoid backbone, while A3 incorporates one five-membered ring. Their structures and electronic properties have been investigated by means of scanning tunneling microscopy, noncontact atomic force microscopy and scanning tunneling spectroscopy complemented with theoretical calculations. Our results provide access to open-shell NGs with a combination of non-benzenoid topologies previously precluded by conventional synthetic procedures.

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“…We have recently achieved on-surface syntheses of dihydroindenofluorene and indenofluorene polymers 3 and 4 (Fig. 1), respectively, through C-H activation of benzylic methyl groups installed on polyphenylenes, leading to the formation of five-membered rings with methylene-and methine-bridges [35][36][37]. We thus considered the structural extension of AGNR edges with five-membered rings by employing the same concept.…”

Section: Introductionmentioning

confidence: 99%

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

Giovannantonio

Urgel

et al. 2021

Nano Res.

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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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On-Surface Synthesis of Oligo(indenoindene)

Abstract: Recently, we have established on-surface syntheses of indenofluorene polymers by utilizing oxidative cyclization of methyl groups against phenylene rings of polyphenylene backbones, 25,26 an alternative strategy to dehydrogenation of

Cited by 34 publications

References 39 publications

Conformational control over π-conjugated electron pairing in 1D organic polymers

Conformational control over π-conjugated electron pairing in 1D organic polymers

Defect-Induced π-Magnetism into Non-Benzenoid Nanographenes

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

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