Exchange of rings shows off molecular machine's clever trick

By passing a small ring through a larger ring, researchers have created a rotaxane with a fundamentally new motion that could be used in future molecular machines. ‘This paper would require me to add a new section to [my book’s] chapter on the movement and stereochemistry of rotaxanes because the motion is so new,’ says Carson Bruns, at the University of Colorado, Boulder in the US, who co-authored a book on mechanically interlocked molecules in 2016 and was not involved in this new work.