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International researchers have used the newest instrument at the Science and Technology Facilities Council’s ISIS Neutron and Muon Source to form and study interlocked self-assembled rings, made solely from one molecular ingredient. This could lead to the development of new materials in the future and has the potential to advance the development of molecular machines.

The scientists have for the very first time synthesised a chain of single molecule interlocking rings that resemble the iconic symbol of the Olympic Games. The chain was created via molecular self-assembly without the use of an additional molecular template.

Dr Robert Dalgliesh is an Instrument Scientist at ISIS Neutron and Muon Source. He yesterday said:

“Our newest Small Angle Scattering (SANS) instrument, ZOOM, was used to provide unique, missing information on the internal structure of the single molecule rings rapidly. The measurements performed with ZOOM complemented X-ray data collected at Diamond Light Source, providing a fantastic demonstration of how this technique can help reveal crucial information to complete a study.”

This experiment builds on the 2016 Nobel Prize-winning work of Jean Pierre Sauvage, J. Fraser Stoddart and Bernard L. Feringa for their work developing molecular machines – molecules with controllable movements, which can perform a task when energy is added. Sauvage’s work connected ring-shaped molecules in a chain – or catenane, from the Latin word for chain.

Interlocked molecular structures created by scientists have previously consisted of rings held together by strong chemical bonds. This research, published in Nature, is the first time that scientists have created these structures built up from a single molecule interacting with itself at this scale with such a fine level of control. The structures made by the team were large enough to be observed by atomic force microscopy. Similar structures were previously too small to be observed using this method.

The research team from Japan, Italy, Switzerland and the UK used the new Zoom beamline at ISIS Neutron and Muon Source to analyse and measure the interlocked rings. Each component ring comprised around 600 identical small molecules, or monomers. These monomers first assemble into six-membered flat “rosettes", which then collectively stack to form a ring. When the group attempted to remove any material from the rings that had not assembled, they found that adding hot monomer solutions enables new assemblies on the surface of the rings, a process known as secondary nucleation. This allowed them to create molecular chains of up to 22 rings.

In the future, the ZOOM beamline could be used to examine in more detail the unique physical properties of single molecule chains such as these, enabling scientists to investigate how they could be used to create artificial molecular machines.

Notes

For more information on the experiment, read ISIS Neutron and Muon Source’s highlight

'Self-assembled poly-catenanes from supramolecular toroidal building blocks' is published in Nature. DOI: 10.1038/s41586-020-2445-z