A multi-state single-molecule switch actuated by rotation of an encapsulated cluster within a fullerene cage

We demonstrate a single-molecule switch based on tunneling electron-driven rotation of a triangular Sc3N cluster within an icosahedral C80 fullerene cage among three pairs of enantiomorphic configurations. Scanning tunneling microscopy imaging of switching within single molecules and electronic structure theory identify the conformational isomers and their isomerization pathways. Bias-dependent action spectra and modeling identify the antisymmetric stretch vibration of Sc3N cluster to be the gateway for energy transfer from the tunneling electrons to the cluster rotation. Hierarchical switching of conductivity through the internal cluster motion among multiple stationary states while maintaining a constant shape, is advantageous for the integration of endohedral fullerene-based single-molecule memory and logic devices into parallel molecular computing architectures.