Molecule builds itself together

"Bonnane" as a basic building block of ultra-small machines

Dr. Frauke Schelhase and Professor dr. Fritz Vögtle with the Bonnan model. © Frank Luerweg / Uni Bonn
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An axle on which two connected tires sit, with a stopper at each end to prevent the tires from falling down. This is what a molecule looks like that will assemble itself and serve as a building block for ultra-small engines in the future. Chemists at the University of Bonn have synthesized it over an eight-year period.

Her work is expected to make Bonn even better known to chemists worldwide: the creators have christened the new class of molecules "Bonnane" - the place where they first saw the light of day.

If you want to know what a Bonnan looks like, Fritz Vögtle can help you: In the office of the emeritus chemistry professor, there is a model of the molecule. It's about 40 centimeters long - 100 million times as big as it actually is. If you were to inflate a pea by the same factor, it would have a diameter of 500 kilometers. With a special microscope you can actually make the individual parts of the molecule visible. "Look - these are the 'tires' that we've threaded over the axle, " says Vögtle, pointing to the shot in front of him. "It's fascinating to be able to really see what we synthesized once."

For eight years, his working group has been developing a synthesis strategy - an international effort that, for example, involved working groups from Japan and Humboldt fellows from China, Iran and the Ukraine. The result is a kind of "recipe": Anyone who sticks to it can reconstruct the Bonnan in a series of steps. "There is a lot of work in this recipe, " emphasizes Vögtle employee Frauke Schelhase.

"For example, we had to design 'tires' that, to a certain extent, slide themselves onto the axle." display

Supramolecular interactions

Because the molecule is composed of different parts together. The mainspring for this are the so-called "supramolecular interactions" - in principle nothing more than weak attraction or repulsion forces between the components, which ensure that they orientate themselves correctly - as if they are aligned with a template. "Nature works in a similar way, " says Schelhase. "Even there, molecules self-assemble into complex compounds."

In Bonn, a Collaborative Research Center "Chemical Stencils" has been working for years to understand the mechanisms behind it. Only with this support were the results possible.

In the Bonnan two tires sit side by side on an axle. A cross brace between them ensures that they move in sync with each other. Above all, this cross-brace required all the art of chemists: Finally, it should later sit exactly in the right place.

On the way to the molecular motor

Thanks to it, however, even such complicated structures as "molecular couplings" can be built: "If we put a smaller molecular disk on the axle and pinch it between the two tires, it will spin like a clutch disk", explains V gtle. "In the next ten years there will be a synthetic molecular motor", he is convinced. "This is no longer a vision, but highly topical research." Nature has already demonstrated it: There are already biological engines that drive about the rotating Gei eln the bacteria.

Further developed Bonnanes could become important components of future nanomachines. The chemists used the name to commemorate their hometown. A similar honor has so far only two other cities: the Australian Sydney ("Sydnon") and the Bavarian capital ("M nchnon").

(idw - University Bonn, 02.01.2007 - DLO)