Nanoribbons with Nonalternant Topology from Fusion of Polyazulene: Carbon Allotropes beyond Graphene

Graphene nanoribbons (GNRs) are quasi‐1D graphene strips, which have attracted attention as a novel class of semiconducting materials for various applications in electronics and optoelectronics. GNRs exhibit unique electronic and optical properties, which sensitively depend on their chemical structures, especially the width and edge configuration. Therefore, precision synthesis of GNRs with chemically defined structures is crucial for their fundamental studies as well as device applications. In contrast to top‐down methods, bottom‐up chemical synthesis using tailor‐made molecular precursors can achieve atomically precise GNRs. Here, the synthesis of GNRs on metal surfaces under ultrahigh vacuum (UHV) and chemical vapor deposition (CVD) conditions is the main focus, and the recent progress in the field is summarized. The UHV method leads to successful unambiguous visualization of atomically precise structures of various GNRs with different edge configurations. The CVD protocol, in contrast, achieves simpler and industry‐viable fabrication of GNRs, allowing for the scale up and efficient integration of the as‐grown GNRs into devices. The recent updates in device studies are also addressed using GNRs synthesized by both the UHV method and CVD, mainly for transistor applications. Furthermore, views on the next steps and challenges in the field of on‐surface synthesized GNRs are provided.

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Section: Recent Progress In the Surface‐assisted Synthesis Of Gnrsmentioning

confidence: 99%

“…These two different structures are determined by the relative positions of the fused polyazulene chains. [ 84 ]…”

Section: Recent Progress In the Surface‐assisted Synthesis Of Gnrsmentioning

confidence: 99%

Graphene Nanoribbons: On‐Surface Synthesis and Integration into Electronic Devices

2020

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“…Furthermore, some on-surface reactions, such as the Ullmann-type coupling involve halogenated precursors. Information about the influence of the surface on the halogen bonds can help to better understand the pathways and mechanisms of such on-surface reactions, what is important for designing new materials with unique properties 31 – 33 .…”

Section: Introductionmentioning

confidence: 99%

Surface-controlled reversal of the selectivity of halogen bonds

et al. 2020

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Intermolecular halogen bonds are ideally suited for designing new molecular assemblies because of their strong directionality and the possibility of tuning the interactions by using different types of halogens or molecular moieties. Due to these unique properties of the halogen bonds, numerous areas of application have recently been identified and are still emerging. Here, we present an approach for controlling the 2D self-assembly process of organic molecules by adsorption to reactive vs. inert metal surfaces. Therewith, the order of halogen bond strengths that is known from gas phase or liquids can be reversed. Our approach relies on adjusting the molecular charge distribution, i.e., the σ-hole, by molecule-substrate interactions. The polarizability of the halogen and the reactiveness of the metal substrate are serving as control parameters. Our results establish the surface as a control knob for tuning molecular assemblies by reversing the selectivity of bonding sites, which is interesting for future applications.

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“…Azulene is a building block with a prototypical non‐alternant aromatic π‐electron system, which has recently attracted attention in surface chemistry, organic electronics, and related areas . Non‐alternant aromatic π‐electron systems typically contain odd‐numbered rings such as pentagons and heptagons.…”

Section: Introductionmentioning

confidence: 99%

The Macrocycle versus Chain Competition in On‐Surface Polymerization: Insights from Reactions of 1,3‐Dibromoazulene on Cu(111)

Krug¹,

Nieckarz

Fan³

et al. 2020

Chemistry A European J

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Ring/chain competition in oligomerization reactions represents a long‐standing topic of synthetic chemistry and was treated extensively for solution reactions but is not well‐understood for the two‐dimensional confinement of surface reactions. Here, the kinetic and thermodynamic principles of ring/chain competition in on‐surface synthesis are addressed by scanning tunneling microscopy, X‐ray photoelectron spectroscopy, and Monte Carlo simulations applied to azulene‐based organometallic oligomers on Cu(111). Analysis of experiments and simulations reveals how the ring/chain ratio can be controlled through variation of coverage and temperature. At room temperature, non‐equilibrium conditions prevail and kinetic control leads to preferential formation of the entropically favored chains. In contrast, high‐temperature equilibrium conditions are associated with thermodynamic control, resulting in increased yields of the energetically favored rings. The optimum conditions for ring formation include the lowest possible temperature within the regime of thermodynamic control and a low coverage. The general implications are discussed and compared to the solution case.

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Nanoribbons with Nonalternant Topology from Fusion of Polyazulene: Carbon Allotropes beyond Graphene

Cited by 169 publications

References 63 publications

Graphene Nanoribbons: On‐Surface Synthesis and Integration into Electronic Devices

Graphene Nanoribbons: On‐Surface Synthesis and Integration into Electronic Devices

Surface-controlled reversal of the selectivity of halogen bonds

The Macrocycle versus Chain Competition in On‐Surface Polymerization: Insights from Reactions of 1,3‐Dibromoazulene on Cu(111)

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