Conformational dependence of tag induced intramolecular STM contrast in hexaphenylbenzene molecules

Chemically tagged hexaphenylbenzene molecules physisorbed on Au(1 1 1) surface display their tag differently under STM as compared to their physisorption on a Cu(1 1 1) surface. Our STM findings complemented by First Principles and Quantum Chemistry calculations have attributed this difference to two different conformations adopted by these molecules on Au(1 1 1) in comparison to its one conformation on Cu(1 1 1). The demonstration of the sensitivity of the tag to its electronic or chemical environment would have important implications in designing single molecule machinery where the motion of the molecule is to be discerned by tracking its tag induced intramolecular STM contrast.