On-surface synthesis and characterization of anti-aromatic cyclo[12]carbon and cyclo[20]carbon.

Cyclo[n]carbons have recently attracted significant attention owing to their geometric and electronic structures remaining largely unexplored in the condensed phase. In this work, we focus on two anti-aromatic cyclocarbons, namely C and C. By designing two fully halogenated molecular precursors both including 4-numbered rings, we further extend the on-surface retro-Bergman ring-opening reaction, and successfully produce C and C.

Scanning Tunneling Spectroscopy Investigation of Au--acetylide Networks on Au(111): The Influence of Metal-Organic Hybridization.

Graphdiyne (GDY) is an appealing two-dimensional carbon material, but the on-surface synthesis of a single layer remains challenging. Demetalation of well-crystalline metal acetylide networks, though in its infancy, provides a new avenue to on-surface synthesized GDY substructures. In spite of the synthetic efforts and theoretical concerns, there are few reports steeped in elaborate characterization of the electronic influence of metalation.

On-surface synthesis and characterization of polyynic carbon chains.

Carbyne, an elusive -hybridized linear carbon allotrope, has fascinated chemists and physicists for decades. Due to its high chemical reactivity and extreme instability, carbyne was much less explored in contrast to the -hybridized carbon allotropes such as graphene. Herein, we report the on-surface synthesis of polyynic carbon chains by demetallization of organometallic polyynes on the Au(111) surface; the longest one observed consists of ∼60 alkyne units (120 carbon atoms).

On-surface synthesis of aromatic cyclo[10]carbon and cyclo[14]carbon.

All-carbon materials based on sp-hybridized atoms, such as fullerenes, carbon nanotubes and graphene, have been much explored due to their remarkable physicochemical properties and potential for applications. Another unusual all-carbon allotrope family are the cyclo[n]carbons (C) consisting of two-coordinated sp-hybridized atoms. They have been studied in the gas phase since the twentieth century, but their high reactivity has meant that condensed-phase synthesis and real-space characterization have been challenging, leaving their exact molecular structure open to debate.

On-Surface Synthesis of a Carbon Nanoribbon Composed of 4-5-6-8-Membered Rings.

From the structure point of view, there are a number of ways of tiling a carbon sheet with different polygons, resulting in prospects of tailoring electronic structures of low-dimensional carbon nanomaterials. However, up to now, the experimental fabrication of such structures embedded with periodic nonhexagon carbon polygons, especially ones with more than three kinds, is still very challenging, leaving their potential properties unexplored. Here we report the bottom-up synthesis of a nanoribbon composed of 4-5-6-8-membered rings via lateral fusion of polyfluorene chains on Au(111).

Bottom-Up Synthesis of Metalated Carbyne Ribbons via Elimination Reactions.

Elimination reactions are one of the most important reactions in organic synthesis, especially in the formation of alkenes and alkynes. Herein, based on scanning tunneling microscopy, we report the bottom-up synthesis of one-dimensional carbyne-like nanostructures, metalated carbyne ribbons with the incorporation of Cu or Ag atoms, through α- and β-elimination reactions of tetrabromomethane and hexabromoethane on surfaces. Density functional theory calculations demonstrate a width-dependent band gap modulation within these ribbon structures, which is affected by interchain interactions.

Real-space visualization of sequential debromination of polybrominated benzenes on Ag(111).

By a combination of scanning tunneling microscopy imaging and density functional theory calculations, dehalogenation processes of symmetric polyhalogenated benzenes were explored on Ag(111), and a series of intermediate states were captured and visualized in real space. These results reveal a sequential dehalogenation scenario of symmetric polybrominated aromatics, which will broaden the understanding of on-surface dehalogenation reactions.

On-Surface Debromination of CBr: C Ring versus C Chain.

Carbon allotropes comprising sp-hybridized carbon atoms have been investigated for decades for their molecular structure. One of the unsolved mysteries is whether they should take a linear or cyclic configuration in condensed phases due to the lack of atomistic characterizations. Herein, we designed a molecule with a C skeleton as a model system to address this issue, which was achieved by eliminating Br atoms from hexabromobenzene (CBr) molecule on the Ag(111) substrate via thermal treatment.

On-Surface Synthesis of -Carbon Nanostructures.

The on-surface synthesis of carbon nanostructures has attracted tremendous attention owing to their unique properties and numerous applications in various fields. With the extensive development of scanning tunneling microscope (STM) and noncontact atomic force microscope (nc-AFM), the on-surface fabricated nanostructures so far can be characterized on atomic and even single-bond level. Therefore, various novel low-dimensional carbon nanostructures, challenging to traditional solution chemistry, have been widely studied on surfaces, such as polycyclic aromatic hydrocarbons, graphene nanoribbons, nanoporous graphene, and graphyne/graphdiyne-like nanostructures.

On-Surface Synthesis of One-Dimensional Carbon-Based Nanostructures via C-X and C-H Activation Reactions.

The past decades have witnessed the emergence of low-dimensional carbon-based nanostructures owing to their unique properties and various subsequent applications. It is of fundamental importance to explore ways to achieve atomically precise fabrication of these interesting structures. The newly developed on-surface synthesis approach provides an efficient strategy for this challenging issue, demonstrating the potential of atomically precise preparation of low-dimensional nanostructures.