Representation of the electrons in the “half-Möbius”-shaped molecule
IBM Research and the University of Manchester
Chemists have discovered a new molecular shape, and it is twice as odd as the twisty Möbius strip.
The Möbius strip is a looped band with a twist, such that something tiny, such as an ant, would have to go around the loop twice to return to where it started on the same side of the strip.
Igor Rončević at the University of Manchester in the UK and his colleagues now discovered a molecule with an even stranger “half-Möbius” shape. Their experiment may be the first step towards a new way to engineer useful molecules by tuning their 3D shapes, or topology.
“This molecule is very new and very unexpected. The appeal is not just that we made a molecule with an unusual topology, but we also showed that this topology is possible, and no one really thought about it,” he says.
To make the molecule, the researchers used 13 carbon atoms and two chlorine atoms assembled into a ring-like shape on a thin surface of gold at an extremely cold temperature. They used two specialised microscopes – an atomic force microscope and a scanning tunnelling microscope – to control the atoms and map the properties of their electrons. In this type of molecule, the electrons aren’t tightly bound to their atoms; instead, the electrons spread across specific regions around the atoms like tiny waves of matter.
It was the interactions between these electrons that produced the never-before-seen twistiness in the molecule. If a tiny quantum creature travelled along the atoms, it would take it four circuits of the ring to return to its starting point.
By prodding the molecule with a small electromagnetic pulse, the team was able to switch the molecule’s twist from left-handed to right-handed or to untwist it. The researchers could engineer its topology on demand, creating another way for chemists to manipulate molecules.
To understand the new molecule and why it could even exist, the team used simulations on both a conventional computer and an IBM quantum computer. Interactions between electrons were crucial for the molecule’s novel twists, and they are difficult to exactly simulate with conventional computers. But quantum computers are already built from interacting quantum objects, so they can perform simulations at a higher level of confidence, says Rončević.
This is an example of how quantum computers can already be useful for real-world chemistry problems, says team member Ivano Tavernelli at IBM.
“This experiment is a remarkable achievement across a number of dimensions: organic chemistry, surface science, nanoscience and quantum chemistry,” says Gemma Solomon at the University of Copenhagen in Denmark.
“This is a beautiful and inspiring study that brings abstract topological concepts vividly into the realm of molecular chemistry,” says Kenichiro Itami at the Japanese scientific institute RIKEN. He says the study is a technical tour de force.
Dongho Kim at Yonsei University in South Korea, a pioneer of past work on Möbius-like molecules, says being able to switch the molecule from one shape to another is particularly interesting, as it could lead to applications in sensors. For instance, molecules could switch in a pre-programmed way when exposed to magnetic fields.
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