Probing the mobility of catenane rings in single molecules

Here we demonstrate for the first time the interrogation of a mechanical link made of catenane rings at the single molecule level. We used AFM-based single molecule force spectroscopy to address the mobility of the rings in a catenane unit of the benzylic amide family. To interface the catenane with the AFM probe, we connected a polymer chain to each of the macrocycles of the [2] catenane. Force-extension profiles in different solvents were then recorded. We show that the catenane ring motions can be detected at the single molecule level and that the ring rotation can be locked or unlocked depending on the solvent.