Advances in scanning probe microscopy at low temperatures and in ultrahigh vacuum conditions have allowed researchers to visualize single-molecule reactions on surfaces with atomic resolution. However, in contrast to organic chemistry in solution, on-surface chemistry is not well developed and only a few reactions have been examined under these conditions with suitable resolution.
Diego Peña, Universidade de Santiago de Compostela, Spain, Leo Gross, IBM Research Zurich, Switzerland, and colleagues have visualized a Diels–Alder reaction taking place in a single molecule (pictured below). The team selected a cyclic strained triyne as a substrate for an intramolecular hexadehydro-Diels–Alder reaction on a Cu(111) surface. The reaction was studied with submolecular resolution by atomic force microscopy (AFM) with CO-functionalized tips. The Diels–Alder reaction led to an aryne, which then undergoes a cycloisomerization to give tribenzo[fg,ij,rst]pentaphene.
According to the researchers, the findings could extend the use of the popular Diels–Alder reaction in on-surface synthesis. On-surface intermolecular Diels–Alder reactions could lead to new nanostructures and provide good atom economy.
- An on‐surface Diels‐Alder reaction,
Diego Peña, Jesús Castro-Esteban, Florian Albrecht, Shadi Fatayer, Dolores Pérez, Leo Gross,
Angew. Chem. Int. Ed. 2021.