A research team studies the reactivity of single molecules under controlled microscopic conditions

Researchers around the world are working to develop efficient materials to convert CO2 into usable chemical substances, a particularly urgent task given global warming. A team from the University of Göttingen, Germany, and the National Institute of Science in Ulsan, South Korea, discovered a promising new approach: catalytically active molecules are nanoconfined, meaning they are placed in an environment that leaves very little space for single molecules – on a surface that serves as a conductive electron supplier. These molecules promote specific chemical reactions. Such hybrid systems exploit both the properties of the molecules and the properties of the substrate. The results were published in Scientists progress.

The first step for the team was to deposit the catalytically active molecules as a vapor on polished silver before examining them with a high-resolution scanning tunneling microscope built in Göttingen. “To our amazement, the molecules magically organize themselves into near-perfect monolayer structures on the surface,” says Lucas Paul, PhD student at the University of Göttingen and co-author of the study.

“In addition to imaging individual molecules, the energy of the injected electrons can be tuned so precisely in the scanning tunneling microscope that chemical reactions can be induced and observed within a single molecule,” explains physicist Professor Martin Wenderoth. Wenderoth led the project with chemist professor Inke Siewert, at the University of Göttingen’s Collaborative Research Center 1073 “Atomic-scale control of energy conversion”. Siewert adds: “We are able to break individual chemical bonds very precisely.”

The researchers show that molecules that are particularly dense on the surface have altered chemical properties. Thus, exclusively for “trapped” molecules, the bond can be broken and later also restored, since the separated part of the molecule can only move very slightly away from the rest of the molecule. “It shows how a lack of space, at the atomic level, can be used to manipulate chemical reactions,” says first author Ole Bunjes, from the University of Göttingen.

The research team hopes that their experiments will contribute to the development of efficient molecular surface systems with precisely determined properties. Furthermore, they want to investigate whether their new system is suitable as a molecular data store.

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