Sir James Fraser Stoddart, who went by Fraser, passed away on 30 December 2024, at the age of 82. The Stoddart group made significant contributions to a range of scientific fields including carbohydrate chemistry, stereochemistry, supramolecular chemistry and metal–organic frameworks (MOFs). The discoveries most associated with Fraser, however, stem from his investigations of interlocked molecules, such as catenanes and rotaxanes.

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Fraser Stoddart

Several excellent obituaries1,2,3 have documented Fraser’s accomplishments. Here, we aim to offer some insights into his philosophy and his distinctive approach to life and science. Whenever possible, we have incorporated Fraser’s own words from his writings4,5,6,7, presentations8,9,10, and personal interactions.

Fraser began his independent career at the University of Sheffield, following a postdoctoral stint at Queen’s University in Canada, where he became fascinated with the chemistry of crown ether compounds. His interest in interlocked molecules can be traced to his three-year secondment at the ICI Corporate Laboratory in the UK7. There, he met Howard Colquhoun (later, at the University of Reading) and together they set out to determine whether crown ether complexation could be extended beyond alkyl ammonium ions to transition metal ammines. In Fraser’s words, “a treasure trove of precious metal complexes was unearthed from the [ICI] basement”11. The pair observed that neutral platinum ammines could in fact form crystalline adducts with crown ethers. Structures of the complexes were solved by Fraser’s long-time collaborator David Williams (Imperial College) using X-ray diffraction. Fraser would get particularly excited whenever a letter — or later, an email — arrived from David with the latest crystal structure.

Fraser and Howard also found that dibenzo-30-crown-10 (DB30C10) could form complexes with the herbicide diquat, an organic dication, and in 1986 they reported a complex of a related crown ether, BPP34C10, with another dication, paraquat. “The X-ray crystal structure was a revelation,” he wrote, and “the pseudorotaxane character of the complex was highly suggestive of the exciting things to come.” Once an organic linker was introduced, the first [2]catenane was in hand. A few years later, in 1991, Fraser reported a two-station molecular shuttle12. “My mind flipped,” he said, “and I could see that we had the basis at least for a switch”11.

Fraser was convinced that chemistry needed a new bond to take it to the next level, and for him this was what he termed the ‘mechanical bond’ — the bond that held two interlocked components together.

After periods at the Universities of Sheffield (1970–1990) and Birmingham (1990–1997), Fraser moved his research group to the US and started a new chapter at UCLA. There, the group began work on the use of dynamic covalent chemistry to access interlocked molecules (leading to the synthesis of Borromean rings), exploring multivalency with carbohydrate-based dendrimers, and expanding research on interlocked molecules toward molecular electronics and machines.

It was during his time at UCLA (1997–2007) that Fraser’s wife, Norma Stoddart, passed away in early 2004 after battling cancer. She had been an integral part of the success of the research group, scientifically and in countless other ways. Norma was the love of his life, Fraser said, and “the matriarch of the Stoddart group for a quarter of a century”.

Fraser was then recruited to help build up the nanoscience effort at Northwestern University, joining the Chemistry Department in 2008. He felt that moving from a familiar setting to an unfamiliar one periodically was essential for restimulating the imagination. “If you move and create another home, then you have changed your whole psychology,” he said.

The research group grew quickly in the Research Palace, as he called the new laboratory space. Aspects of Stoddart group research came to include cyclodextrin-based MOFs, radical–radical interactions/radical templating to interlocked compounds, as well as precise strategies to control threading and shuttling in ‘molecular pumps’ capable of capturing macrocycles from solution and pushing them against a chemical gradient. This work marked a jump in complexity for Stoddart's interlocked molecules as the emphasis transitioned from switches to machines. Fraser also poured energy into writing, together with co-author Carson Bruns, a textbook on the nature of the mechanical bond.

On 5 October 2016 it was announced that Fraser, along with Jean-Pierre Sauvage (Strasbourg) and Ben Feringa (Groningen), had been named Nobel laureates in chemistry for “the design and synthesis of molecular machines”. One highlight of Nobel Week for Fraser was signing up, with the help of his former student Stuart Cantrill, for a Twitter account. Within a matter of days, the account (@sirfrasersays) had over a thousand followers. It tickled him pink that others began to call him a Twitter Monster because of his numerous posts, which were often supportive of younger members of the chemistry community.

The next three years would prove at times both uplifting and exhausting as Fraser took to the skies on a routine basis: he was on a mission as a self-appointed global ambassador to share with young people something of his personal and scientific journey, and to provide encouragement to reach for greatness. It also became commonplace for him to meet with heads of state, including in the Oval Office and the Great Hall of the People. “I’ve been trying to adjust to my new life as a minor celebrity,” he told C&E News in early 2017.

In 2023, Fraser moved his group to the University of Hong Kong, where he took up a chair in contemporary chemistry and continued mentoring around twenty postdoctoral scholars.

Fraser came to look upon himself as a global citizen. “I hail from Scotland,” he remarked in one speech. “The Scots have had for centuries an attitude towards their small position on the globe of being much larger than just a little country. I was brought up not to think in an inclusive way about a very small group, but to think on a larger scale.” He embraced fully the international nature of science and believed that it ‘takes a village’ when it comes to solving big challenges in chemistry. It is therefore not a surprise that Fraser was a strong proponent of collaborative research, and his publications are littered with co-authors from across the globe.

Sir Edmund Hirst, Fraser’s PhD mentor at Edinburgh, had told him: “Identify a big problem, Stoddart.” This piece of advice became something of a mantra that members of the Stoddart group would hear on a regular basis. He fully expected that the brightest “lads and lasses” in the group would launch their independent careers by taking up scientific challenges “that I would be too scared or quite unable to touch, i.e., the best should be a lot better than me, or I surely have not been a good mentor!”

As a native son of Auld Reekie (Edinburgh), Fraser’s advice would frequently come in the form of Scottish phases, and he delighted in teaching them to his students. On occasion, he would utter a phase that would leave group members — including the Scots among them — looking bewildered half the time. Here are just a few favourite Fraser sayings that we were able to translate.

  • “Go set the heather on fire” — cause great excitement; do great things and make your mark.

  • “Mony a mickle maks a muckle” — collectively, small changes can make a big difference.

  • “There will be shouting from the rafters” — sharing of exciting news.

  • “This is a box of frogs” — mad, crazy.

  • “You played a blinder!” — well done!

  • “You will get there on Shanks’ pony” — on foot.

  • “Your references are a pig’s breakfast” — a mess.

Whether it was in Scottish vernacular or not, Fraser was always available to give advice to young scientists, irrespective of whether they were members of his group. Since his passing all of us have been contacted by researchers across the globe who have related their own stories of how Fraser was instrumental in helping shape their lives and careers. In his drive to shape creative chemists he applied a thousand brush strokes and was patient with others’ development as scientists. In the latter half of his career, Fraser would often end his lectures by sharing life lessons learned. It seems appropriate to conclude this article with some of these insights (Fig. 1). He insisted that his life was not primarily about research, but rather about the training of young people in research. There is perhaps no greater legacy.

Fig. 1
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Some advice from Sir Fraser that he commonly showed at the end of his talks.

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