When the chemistry is (not) right: Influence of the microscopic environment

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Topography of periodically arranged molecules on a silver surface. Photo: Ole Bu
Topography of periodically arranged molecules on a silver surface. Photo: Ole Bunjes
Research team investigates reactivity of single molecules under controlled conditions

Researchers around the world are working to develop efficient materials to convert CO2 into usable chemical substances. This is especially important in light of global warming. A team from the University of Göttingen and the Ulsan National Institute for Science, South Korea, has found a promising approach: Catalytically active molecules are anchored to a surface that serves as a conductive electron supplier. The molecules promote the chemical reaction. Such hybrid systems harness both the properties of the molecules and the properties of the support material. The results have appeared in the journal Science Advances.

In a first step, the team steamed the catalytically active molecules onto shiny silver before examining them with a high-resolution scanning tunneling microscope built in Göttingen. -To our great amazement, the molecules arrange themselves as if by magic into nearly perfect single-layer structures on the surface,- says Lucas Paul, co-author of the study.

-In addition to imaging individual molecules, the energy of the injected electrons can be adjusted so precisely in the scanning tunneling microscope that chemical reactions can be induced and observed in a single molecule," explains physicist Martin Wenderoth, who led the project together with chemist Inke Siewert in Collaborative Research Center 1073 -Atomic Scale Control of Energy Conversion. -We can precisely break individual chemical bonds," adds Siewert.

The researchers were able to show that molecules that are particularly densely packed on the surface exhibit altered chemical properties. Thus, only the -crowded- molecules can have their bonds broken and subsequently restored, since the separated part of the molecule can only move a small distance away from the rest of the molecule. -This shows how atomic space shortages can be used to manipulate chemical reactions,⤠says first author Ole Bunjes.

With their experiments, the team wants to contribute to the development of efficient molecular surface systems with precisely determined properties. They want to further investigate whether the investigated system is suitable as a molecular data storage device.

Original publication: Bunjes et al, -Making and breaking of chemical bonds in single nanoconfined molecules-, Science Advances 2022: DOI: 10.1126/sciadv.abq7776https://www.science.org/­doi/10.1126/­sciadv.abq7776