  Single molecular rotor is an important component for constructing bot-tom-up
molecular mechanical machines and a window for shedding light on complex
physical and chemical questions about motions of organic molecules on surfaces.
Stability of each component in such a molecular construction site is a crucial
prerequisite. To realize a stable stepwise rotation of a molecule by a low
temperature scanning tunneling microscope (LT-STM), atomic scale axles is
particularly important. An ideal atomic scale axle is expected to balance
between anchoring and mobility of rotating a single molecule on a metal surface
under external excitations. In this Chapter, several chemical anchoring
strategies on how to pin a molecular rotor are tested and discussed.
Tip-induced manipulation and motion analysis are used as tools to investigate
the properties and functionality of the proposed strategies.
