Controlled room-temperature positioning of individual molecules: Molecular flexure and motion

Two-dimensional positioning of intact individual molecules was achieved at room temperature by a controlled lateral ''pushing'' action of the tip of a scanning tunneling microscope. To facilitate this process, four bulky hydrocarbon groups were attached to a rigid molecule. These groups maintained sufficiently strong interactions with the surface to prevent thermally activated diffusional motion, but nevertheless allowed controllable translation. Simulations demonstrated the crucial role of flexure during the positioning process. These results outline the key role of molecular mechanics in the engineering of predefined properties on a molecular scale.