This molecule puts a new twist on the Möbius strip

A new molecule takes an unexpected turn.

Scientists created half-Möbius molecules, similar to the Möbius strips common in math classes, but half as twisty. It’s a type of topology, or geometrical structure, that is new to molecules, scientists report March 5 in Science.

A Möbius strip is a mathematical oddity that can be made by connecting the ends of a thin band of paper, but twisting one end by 180 degrees. If you run your finger along the loop of paper, you must go around twice before your finger returns to where you started. Scientists dreamed up the idea of a molecule with the topology of a Möbius strip in the 1960s, and since then, researchers have created multiple versions of them.

But half-Möbius molecules weren’t on chemists’ radars until now. In the newly created molecules, electrons can move in regions of space set by a twisted path that rotates 90 degrees in each revolution. That’s half as twisted as a Möbius strip, and it means that four circumnavigations of the path — instead of two — are needed to return to the starting point.

The molecules consist of 13 carbon atoms, arranged in a ring, with two chlorine atoms attached. Those chlorine atoms can impart a twist to the molecule that allows it to form the half-Möbius geometry. Atomic force microscopy and scanning tunneling microscopy, alongside calculations made using a quantum computer, helped confirm the molecule’s structure.

The scientists could even manipulate the molecules’ topology. By giving a molecule some energy, the researchers were able to switch it from a half-Möbius configuration to one with no twist.

Half-Möbius molecules are uncharted territory, so potential applications for the molecules are distant and unclear, says chemist Igor Rončević of the University of Manchester in England. “No one really thought that this sort of thing could exist.”