Site-Specific Adsorption of Aromatic Molecules on a Metal/Metal Oxide Phase Boundary.

Nanostructured surfaces are ideal templates to control the self-assembly of molecular structures toward well-defined functional materials. To understand the initial adsorption process, we have investigated the arrangement and configuration of aromatic hydrocarbon molecules on nanostructured substrates composed of an alternating arrangement of Cu(110) and oxygen-reconstructed stripes. Scanning tunneling microscopy reveals a preferential adsorption of molecules at oxide phase boundaries.

Quantitative assessment of intermolecular interactions by atomic force microscopy imaging using copper oxide tips.

Atomic force microscopy is an impressive tool with which to directly resolve the bonding structure of organic compounds. The methodology usually involves chemical passivation of the probe-tip termination by attaching single molecules or atoms such as CO or Xe (refs ). However, these probe particles are only weakly connected to the metallic apex, which results in considerable dynamic deflection.

Intermolecular On-Surface σ-Bond Metathesis.

Silylation and desilylation are important functional group manipulations in solution-phase organic chemistry that are heavily used to protect/deprotect different functionalities. Herein, we disclose the first examples of the σ-bond metathesis of silylated alkynes with aromatic carboxylic acids on the Ag(111) and Au(111) surfaces to give the corresponding terminal alkynes and silyl esters, which is supported by density functional theory calculations and further confirmed by X-ray photoelectron spectroscopy analysis. Such a protecting group strategy applied to on-surface chemistry allows self-assembly structures to be generated from molecules that are inherently unstable in solution and in the solid state.

Substrate-Mediated C-C and C-H Coupling after Dehalogenation.

Intermolecular C-C coupling after cleavage of C-X (mostly, X = Br or I) bonds has been extensively studied for facilitating the synthesis of polymeric nanostructures. However, the accidental appearance of C-H coupling at the terminal carbon atoms would limit the successive extension of covalent polymers. To our knowledge, the selective C-H coupling after dehalogenation has not so far been reported, which may illuminate another interesting field of chemical synthesis on surfaces besides in situ fabrication of polymers, i.

Understanding molecular self-assembly of a diol compound by considering competitive interactions.

With a combination of scanning tunneling microscopy and density functional theory, effects on molecular self-assembly involving two distinct chemical groups were investigated. We analyzed the influence of the individual functional units in the adsorbate and extracted the dominating contributions to the adsorption behaviour. The viability of such a systematic approach to study self-assembled structures by considering the interplay between substrate effects and molecular design is demonstrated.

Submolecular Imaging by Noncontact Atomic Force Microscopy with an Oxygen Atom Rigidly Connected to a Metallic Probe.

In scanning probe microscopy, the imaging characteristics in the various interaction channels crucially depend on the chemical termination of the probe tip. Here we analyze the contrast signatures of an oxygen-terminated copper tip with a tetrahedral configuration of the covalently bound terminal O atom. Supported by first-principles calculations we show how this tip termination can be identified by contrast analysis in noncontact atomic force and scanning tunneling microscopy (NC-AFM, STM) on a partially oxidized Cu(110) surface.

On-surface reductive coupling of aldehydes on Au(111).

On-surface synthesis of a polyphenylene vinylene oligomer via reductive coupling of a terephthalaldehyde derivative on Au(111) is reported. Scanning tunneling microscopy and photoelectron spectroscopy experiments confirmed oxygen dissociation and its desorption from the surface. Density functional theory calculations provided a reasonable reaction mechanism involving reactive sites on the substrate.

Surface supported gold-organic hybrids: on-surface synthesis and surface directed orientation.

The surface-assisted synthesis of gold-organic hybrids on Au (111) and Au (100) surfaces is repotred by thermally initiated dehalogenation of chloro-substituted perylene-3,4,9,10-tetracarboxylic acid bisimides (PBIs). Structures and surface-directed alignment of the Au-PBI chains are investigated by scanning tunnelling microscopy in ultra high vacuum conditions. Using dichloro-PBI as a model system, the mechanism for the formation of Au-PBI dimer is revealed with scanning tunnelling microscopy studies and density functional theory calculations.

On-surface azide-alkyne cycloaddition on Au(111).

We present [3 + 2] cycloaddition reactions between azides and alkynes on a Au(111) surface at room temperature and under ultrahigh vacuum conditions. High-resolution scanning tunneling microscopy images reveal that these on-surface cycloadditions occur highly regioselectively to form the corresponding 1,4-triazoles. Density functional theory simulations confirm that the reactions can occur at room temperature, where the Au(111) surface does not participate as a catalytic agent in alkyne C-H activation but acts solely as a two-dimensional constraint for the positioning of the two reaction partners.