Controlled Room-Temperature Positioning of Individual Molecules: Molecular Flexure and Motion

Two-dimensional positioning of intact individual molecules using scanning tunneling microscopy at room temperature is described. This is achieved by a controlled lateral ``pushing'' action of the tip. The process is facilitated by attachment of four bulky hydrocarbon groups to a rigid molecule which maintain sufficiently strong interactions with the surface to prevent thermally activated diffusional motion but nevertheless allow controllable translation. Simulations demonstrate the crucial role of flexure during the positioning process.