Molecules with a triple helix

Researchers have now succeeded in designing the first ever Möbius chain-style coiled molecule. Thanks to their extraordinary quantum properties, these structures are important for new applications in molecular electronics and optoelectronics.

These are three-dimensional structures and still have one side: Möbius strips. These convoluted shapes have only one side and only one lip and challenge our logic and imagination. Researchers have now succeeded in designing the first ever coiled molecule. Thanks to their extraordinary quantum properties, these structures are important for new applications in molecular electronics and optoelectronics.

An international team of researchers, led by chemistry professor Rainer Herges from the University of Kiel, succeeded in designing the first ever coiled molecule with a Möbius strip structure (Wikipedia). Thanks to their special quantum properties, these structures may be important in new applications in the fields of molecular electronics and optoelectronics. In a new paper published by the researchers in the scientific journal Nature Chemistry, they explain how they used a topological trick to prepare these strange molecules.

In 1858, mathematicians Jonathan Benedict Listing and August Ferdinand Mbeuss independently discovered the convoluted strips that have only one side and one lip. Since then, Mobius strips have inspired architects, artists and scientists. Anyone can create a simple model of this structure - take a long piece of tape, twist one end half a turn, then glue it to the other end. Unlike a normal ring, whose rim includes two separate circles, the rim of a Mebios band only includes one circle - if you move your finger along the rim, you complete the movement after visiting all the points of the rim. The topological properties of such a structure are fascinating - for example, if we cut it lengthwise, the strip will not produce, as in a normal strip, two strips - but one strip with twice the diameter and four times the twists.

In the sixties, chemists also became interested in the special topology of these structures since theoretical calculations predicted the receipt of properties that improved one of the most important laws of chemistry related to the stability of molecules. However, it took researchers almost 50 years to produce a simple coiled molecule with such a structure and verify the predictions. The big difficulty is to twist and twist the molecules: like strips made of cardboard or steel they resist twisting and start to return to their original untwisted state when their ends are released. Because of this, the scientists built their molecule in two parts: one part was composed of a regular strap component and the other was pre-shaped in the shape of a belt. A fusion of these two components resulted in the creation of a coiled ring.

At the same time, triangularly wound rings are too stretched to be able to be produced in this way. We see this in everyday life - in order to relieve structural stress, coiled coils wind around themselves, as in telephone cables or coiled irrigation pipes. "The building blocks with which we can build our coiled Möbius molecule are three helical components. They look like short segments of a DNA helix," explains the lead researcher.

Unlike coiled structures, helical molecules are stable. And despite this, it was still not easy to merge the helical units into one Möbius molecule, this in light of the fact that they are chiral (Wikipedia). Chirality is the lack of mirror symmetry of an object. In chemistry, a chiral molecule is a molecule that cannot create an overlap between it and its mirror image through rotation in space. The researchers had to find the right way to combine these three components in order to design the desired molecule. In the end they did succeed in the mission.

"With the help of our strategy, we proved that it is simpler to produce molecular systems with several twists than units with one twist," explains the lead researcher. The new Mobius molecules have interesting electronic and optical properties. These could eventually be used as components in the development of quantum computers. The "quantum bits" could be defined by their topological states - twisted or untwisted, instead of passing/not passing an electric current. Due to their special quantum properties, an electric current induced by a magnetic field inside Möbius molecules flows in the direction opposite to the direction of normal rings.

The news about the study