On-surface synthesis of a phenylene analogue of nonacene.

Cyclobuta[1,2-b:3,4-b']ditetracene - an analogue of nonacene with a cyclobutadiene unit embedded in the central part has been synthesized by the combination of solution and on-surface chemistry. The atomic structure and electronic properties of the product on Au(111) have been determined by high resolution scanning tunnelling microscopy/spectroscopy corroborated by density functional theory calculations. Structural and magnetic parameters derived from theoretical calculations reveal that π conjugation is dominated by radialene-type contribution, with an admixture of cyclobutadiene-like antiaromaticity.

On-Surface Synthesis of Chlorinated Narrow Graphene Nanoribbon Organometallic Hybrids.

Graphene nanoribbons (GNRs) and their derivatives attract growing attention due to their excellent electronic and magnetic properties as well as the fine-tuning of such properties that can be obtained by heteroatom substitution and/or edge morphology modification. Here, we introduce graphene nanoribbon derivatives-organometallic hybrids with gold atoms incorporated between the carbon skeleton and side Cl atoms. We show that narrow chlorinated 5-AGNROHs (armchair graphene nanoribbon organometallic hybrids) can be fabricated by on-surface polymerization with omission of the cyclodehydrogenation reaction by a proper choice of tailored molecular precursors. Finally, we describe a route to exchange chlorine atoms connected through gold atoms to the carbon skeleton by hydrogen atom treatment. This is achieved directly on the surface, resulting in perfect unsubstituted hydrogen-terminated GNRs. This will be beneficial in the molecule on-surface processing when the preparation of final unsubstituted hydrocarbon structure is desired.

Rational synthesis of atomically precise graphene nanoribbons directly on metal oxide surfaces.

Atomically precise graphene nanoribbons (GNRs) attract great interest because of their highly tunable electronic, optical, and transport properties. However, on-surface synthesis of GNRs is typically based on metal surface-assisted chemical reactions, where metallic substrates strongly screen their designer electronic properties and limit further applications. Here, we present an on-surface synthesis approach to forming atomically precise GNRs directly on semiconducting metal oxide surfaces. The thermally triggered multistep transformations preprogrammed in our precursors' design rely on highly selective and sequential activations of carbon-bromine (C-Br) and carbon-fluorine (C-F) bonds and cyclodehydrogenation. The formation of planar armchair GNRs terminated by well-defined zigzag ends is confirmed by scanning tunneling microscopy and spectroscopy, which also reveal weak interaction between GNRs and the rutile titanium dioxide substrate.