James Fraser Stoddart obituary: chemist and nanotechnology pioneer who built molecular machines

An early love of construction toys led the Scottish chemist to thread molecules together, opening up a new field of chemistry

James Fraser Stoddart created a field of chemistry based on threaded and mechanically connected molecules, held together like links of a chain rather than through conventional chemical bonds. He recognized that the motions of the linked components could be exploited to make artificial molecular machinery, a breakthrough for which he shared the 2016 Nobel Prize in Chemistry with Jean-Pierre Sauvage and Bernard L. Feringa. He has died aged 82.

Born in Edinburgh, UK, Stoddart was brought up on a remote farm that lacked electricity. He said that farm living instilled in him “the work ethic of a honeybee”. The young Stoddart played with construction toys such as Meccano, which he later suggested was an inspiration for his building of machines from molecules. After completing a PhD in chemistry at the University of Edinburgh, he took a postdoctoral position at Queen’s University in Kingston, Canada. The parting advice of the University of Edinburgh’s chair of organic chemistry, Edmund Hirst, rang in his ears: “Whatever you do in research, Stoddart, make sure you work on a big problem!”

In 1970, Stoddart returned to the United Kingdom to do a lectureship at the University of Sheffield, and began to search for a problem. The emerging field of supramolecular chemistry — chemistry beyond the molecule — caught his attention. He became intrigued by cyclic molecules called crown ethers, which could bind metal ions and charged organic molecules within their rings.

From 1978, Stoddart spent three years on secondment to the Imperial Chemical Industries (ICI) Corporate Laboratories in Runcorn, UK, while — back in Sheffield — his students prepared a series of transition-metal complexes with crown ethers. Structural similarities between those complexes and the herbicides he had seen at ICI led Stoddart to explore crown ethers that could bind to the weedkiller Paraquat. A visiting Spanish PhD student threaded a paraquat derivative through a crown ether ring, then connected the derivative’s two ends. The result: two cyclic molecules mechanically linked together, called a [2]catenane.

Stoddart’s team then created a [2]rotaxane — a ring-shaped molecule threaded onto a dumbbell-shaped molecule, with the ring darting back and forth between two ‘stations’ on the dumbbell’s shaft. In a 1991 paper, Stoddart termed it a ‘molecular shuttle’, noting: “Insofar as it becomes possible to control the movement of one molecular component with respect to the other in a [2]rotaxane, the technology for building ‘molecular machines’ will emerge.” (P. L. Anelli et al. J. Am. Chem. Soc. 113, 5131–5133; 1991).

He had found his problem. Over the next two decades, the Stoddart group pioneered the field of artificial molecular machinery, producing eye-catching molecular objects that resembled in some aspects their counterparts from the macroscopic world, including a ‘molecular elevator’ and ‘Olympiadane’, a molecular version of the Olympic rings.