Scientists from the Karlsruhe Institute of Technology (KIT) and the University of Marburg have achieved a groundbreaking milestone in organometallic chemistry. They have successfully synthesized nano-sized rings made of stacked sandwich compounds, a chemical compound commonly used as building blocks in this branch of chemistry. Their research findings, published in Nature, represent a significant departure from the traditional linear structure of sandwich complexes.

Sandwich complexes, invented about 70 years ago, consist of two flat aromatic organic rings filled with a central metal atom, akin to slices of bread with filling. By adding multiple layers of “bread” and “filling,” researchers have previously created triple and multiple sandwiches. Among these complexes, ferrocene stands out as a highly stable compound, which earned its discoverers the Nobel Prize in Chemistry in 1973. Ferrocene is employed in various fields, including synthesis, catalysis, electrochemistry, and polymer chemistry.

However, researchers have struggled to arrange sandwich complexes in a ring shape. After considerable effort, the KIT and the University of Marburg team successfully produced nano-sized rings composed of 18 building blocks, forming a cyclocene structure. Depending on the metal used as the “filling” of the sandwich, the nanoring exhibited an orange-colored photoluminescence. Quantum chemical calculations revealed that the driving force behind this ring formation was the energy gained through ring closure. This achievement marks the first instance of cyclic multidecker sandwich compounds and opens doors for potential nanotechnology, materials science, and medicine applications.

The discovery of these cyclic nanometre-scale sandwich complexes represents a significant advancement in organometallic chemistry. With the ability to form closed rings from individual building blocks, researchers have expanded their toolbox for creating new functional organometallic materials. As scientists delve deeper into the properties and potential applications of these innovative cyclocene structures, it is anticipated that further exciting breakthroughs lie ahead.

References

• Karlsruhe Institute of Technology. (2023, August 3). Nanorings: New building blocks for chemistry. Phys.Org. https://phys.org/news/2023-08-nanorings-blocks-chemistry.html
• Münzfeld, L., Gillhuber, S., Hauser, A., Lebedkin, S., Hädinger, P., Knöfel, N. D., Zovko, C., Gamer, M. T., Weigend, F., Kappes, M. M., & Roesky, P. W. (2023). Synthesis and properties of cyclic sandwich compounds. Nature, 620(7972), 92–96. https://doi.org/10.1038/s41586-023-06192-4