Structural Transformation of 2,7‐Dibromopyrene on Au(111) Mediated by Halogen‐Bonding Motifs

Synthesis of a Porous [14]Annulene Graphene Nanoribbon and a Porous [30]Annulene Graphene Nanosheet on Metal Surfaces

The electrical and mechanical properties of graphene-based materials can be tuned by the introduction of nanopores, which are sensitively related to the size, morphology, density, and location of nanopores. The synthesis of low-dimensional graphene nanostructures containing well-defined nonplanar nanopores has been challenging due to the intrinsic steric hindrance. Herein, we report the selective synthesis of one-dimensional (1D) graphene nanoribbons (GNRs) containing periodic nonplanar [14]annulene pores on Ag(111) and two-dimensional (2D) porous graphene nanosheet containing periodic nonplanar [30]annulene pores on Au(111), starting from a same precursor. The formation of distinct products on the two substrates originates from the different thermodynamics and kinetics of coupling reactions. The reaction mechanisms were confirmed by a series of control experiments, and the appropriate thermodynamic and kinetic parameters for optimizing the reaction pathways were proposed. In addition, the combined scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations revealed the electronic structures of porous graphene structures, demonstrating the impact of nonplanar pores on the π-conjugation of molecules.

Surface-assisted fabrication of low-dimensional carbon-based nanoarchitectures

On-surface synthesis, as an alternative to traditional in-solution synthesis, has become an emerging research field and attracted extensive attention over the past decade due to its ability to fabricate nanoarchitectures with exotic properties. Compared to wet chemistry, the on-surface synthesis conducted on atomically flat solid surfaces under ultrahigh vacuum exhibits unprecedented characteristics and advantages, opening novel reaction pathways for chemical synthesis. Various low-dimensional nanostructures have been fabricated on solid surfaces (mostly metal surfaces) based on this newly developed approach. This paper reviews the classic and latest works regarding carbon-based low-dimensional nanostructures since the arrival of on-surface synthesis era. These nanostructures are categorized into zero-, one- and two-dimensional classes and each class is composed of numerous sub-nanostructures. For certain specific nanostructures, comprehensive reports are given, including precursor design, substrate choice, synthetic strategies and so forth. We hope that our review will shed light on the fabrication of some significant nanostructures in this young and promising scientific area.

Initiating Ullmann-like coupling of Br2Py by a semimetal surface

Intensive efforts have been devoted to surface Ullmann-like coupling in recent years, due to its appealing success towards on-surface synthesis of tailor-made nanostructures. While attentions were mostly drawn on metallic substrates, however, Ullmann dehalogenation and coupling reaction on semimetal surfaces has been seldom addressed. Herein, we demonstrate the self-assembly of 2, 7-dibromopyrene (Br₂Py) and the well controllable dehalogenation reaction of Br₂Py on the Bi(111)–Ag substrate with a combination of scanning tunnelling microscopy (STM) and density functional theory calculations (DFT). By elaborately investigating the reaction path and formed organic nanostructures, it is revealed that the pristinely inert bismuth layer supported on the silver substrate can initiate Ullmann-like coupling in a desired manner by getting alloyed with Ag atoms underneath, while side products have not been discovered. By clarifying the pristine nature of Bi–Ag(111) and Ullmann-like reaction mechanisms, our report proposes an ideal template for thoroughly exploring dehalogenative coupling reaction mechanisms with atomic insights and on-surface synthesis of carbon-based architectures.