Metal-Free on-Surface Photochemical Homocoupling of Terminal Alkynes

Abstract

On-surface synthesis involving the homocoupling of aryl-alkynes affords the buildup of bisacetylene derivatives directly at surfaces, which in turn may be further used as ingredients for the production of novel functional materials. Generally, homocoupling of terminal alkynes takes place by thermal activation of molecular precursors on metal surfaces. However, the interaction of alkynes with surface metal atoms often induces unwanted reaction pathways when thermal energy is provided to the system. In this contribution we report about light-induced metal-free homocoupling of terminal alkynes on highly oriented pyrolitic graphite (HOPG). The reaction occurred with high efficiency and selectivity within a self-assembled monolayer (SAM) of aryl-alkynes and led to the generation of large domains of ordered butadiynyl derivatives. Such a photochemical uncatalyzed pathway represents an original approach in the field of topological C-C coupling at the solid/liquid interface.

Covalent‐Bond Formation via On‐Surface Chemistry

“…At room temperature the dimers show low surface mobility and therefore further reaction towards polymeric structures is suppressed. Very recently, also a metal‐free version of this UV light‐induced homocoupling of terminal alkynes was reported on a highly oriented pyrolytic graphite (HOPG) surface …”

Reactivity on and of Graphene Layers: Scanning Probe Microscopy Reveals

“…a adapted with permission from [65]; copyright © 2014 American Chemical Society. e adapted with permission from [72]; copyright © 2016 American Chemical Society electrochemically active groups (Fig. 15a, [80]) can be prepared by conventional self-assembly from solution and characterized using STM (structure) and cyclic voltammetry (CV, electrochemical properties).…”

On‐Surface Photochemistry of Pre‐Ordered 1‐Methyl‐2‐phenyl‐acetylenes: C‐H Bond Activation and Intermolecular Coupling on Highly Oriented Pyrolytic Graphite

“…As a matter of fact, the efficiency of the on‐surface light‐induced reactions tends to be very low, since in many cases the proximity of the substrate (metallic substrates in particular) provides relaxation pathways responsible for quenching the photo‐excited species, with the immediate practical implication being that the chemical reactions are detectable only after many hours of irradiation. Nevertheless, the possibility to use non metallic surfaces like highly oriented pyrolytic graphite (HOPG) or calcite as substrates for photochemical synthesis was also successfully explored as a tentative solution for this bottleneck.…”