  A key step towards building single molecule machines is to control the
rotation of molecules and nanostructures step by step on a surface. Here, we
used the tunneling electrons coming from the tip of a scanning tunneling
microscope to achieve the controlled directed rotation of complex o-MeO-DMBI
molecules. We studied the adsorption of single o-MeO-DMBI molecules on Au(111)
by scanning tunneling microscopy at low temperature. The enantiomeric form of
the molecule on the surface can be determined by imaging the molecule by STM at
high bias voltage. We observed by lateral manipulation experiments that the
molecules chemisorb on the surface and are anchored on Au(111) with an
oxygen-gold bond via their methoxy-group. Driven by inelastic tunneling
electrons, o-MeO-DMBI molecules can controllably rotate, stepwise and
unidirectional, either clockwise or counterclockwise depending on their
enantiomeric form.

Mesoscale and Nanoscale Physics