News Release

Scientists twist chemical bonds beyond their limits

Embargoed until 1600 GMT on Monday 6 March 2023

Peer-Reviewed Publication

Durham University

A group of scientists from Durham University and University of York have twisted molecules to their breaking point in order to challenge the understanding of chemical bonds.

The researchers explored how far the chemical bonding in an aromatic ring can be twisted before its aromatic bonding breaks.

They achieved this by making overcrowded aromatic rings. Rather than benzene, they used tropylium, which shares electrons around a ring of seven carbon atoms.

Each of these carbon atoms can be functionalised and having seven attachment points in the ring, rather than the six carbon atoms of benzene, allowed the researchers to cram more groups around the edge of the aromatic ring, causing more strain.

The researchers found that low levels of overcrowding made the ring twist, but without breaking its aromatic bonding.

By adding progressively larger groups around the edge of the ring, the team twisted the ring further, eventually causing the aromatic bonding to break.

The electrons no longer circle the seven carbon atoms and instead, the ring pinches across its middle to form two smaller flat rings.

Surprisingly, the researchers found there is a balance point, where the ring jumps back and forth between aromatic structure and the two smaller rings. One molecule made in this study spends 90% of its time as the pinched structure and 10% of its time as a larger aromatic ring.

Full study results have been published in the journal Nature Chemistry.

Reflecting on the study results, Dr Paul McGonigal of University of York, said: “In these overcrowded molecules, strain and aromatic bonding are delicately balanced. The structure, properties, and potential applications of a material are ultimately determined by this balance.

“The precise control over the twisting of our molecules is unprecedented.

“We were not only able to twist an aromatic molecule up to the maximum amount of strain it can tolerate, but also to discover what happens when we push beyond that limit. We hope this investigation is a step towards us being able to more routinely turn aromatic bonding ‘off’ and ‘on’ in a controlled manner.”

Project lead investigator, Promeet Saha of Durham University, said: “The reversible pinching and reopening of an aromatic ring are truly remarkable.

“Aromatic bonding is such a powerful stabilising force that we usually think of it being a constant presence. However, our findings demonstrate that it can be surprisingly dynamic.”

Chemical bonding in aromatic molecules is key to the structure, stability and function of chemicals such as drugs and plastics.

The research has been funded by the Engineering and Physical Sciences Research Council (EPSRC).


Media Information

Dr Paul McGonigal from University of York/Durham University is available for interview and can be contacted on

Alternatively, please contact Durham University Communications Office for interview requests on


Associated images are available via the following link:

Source Information

“Rupturing aromaticity by periphery”, (2023), Promeet K. Saha, Abhijit Mallick, Andrew T. Turley, Aisha N. Bismillah, Andrew Danos, Andrew P. Monkman, Alyssa-Jennifer Avestro, Dmitry S. Yufit & Paul R. McGonigal, Nature Chemistry.

The paper will be available online after the embargo lifts:

An embargoed copy of the paper is available from Durham University Communications Office. Please email

About Durham University

Durham University is a globally outstanding centre of teaching and research based in historic Durham City in the UK.

We are a collegiate university committed to inspiring our people to do outstanding things at Durham and in the world.

We conduct boundary-breaking research that improves lives globally and we are ranked as a world top 100 university with an international reputation in research and education (QS World University Rankings 2023).

We are a member of the Russell Group of leading research-intensive UK universities and we are consistently ranked as a top 10 university in national league tables (Times and Sunday Times Good University Guide, Guardian University Guide and The Complete University Guide).

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END OF MEDIA RELEASE – issued by Durham University Communications Office.

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