Electron stimulation of internal torsion of a surface-mounted molecular rotor.

A molecular rotor which includes a central rotator group was investigated by scanning tunneling microscopy at 4.9 K as it was grafted on a Cu(111) surface via its two terminal groups. Topographs with submolecular resolution revealed several distinct molecular conformations which we attribute to different angular orientations of the rotator and which are locally stable states according to density functional theory calculations.