The First Molecular Wheel: A Theoretical Investigation

Recently, the first molecular nanowheel was synthesized and characterized from Scanning Tunneling Microscope (STM) experiments. It was demonstrated that a specifically designed hydrocarbon molecule (C 44 H 24 ) could roll on a copper substrate along the [110] surface direction. In this work we report a preliminary theoretical analysis of the isolated molecule and of its rolling processes on different Cu surfaces. We have used ab initio and classical molecular dynamics methods. The simulations showed that the rolling mechanism is only possible for the [110] surface. In this case, the spatial separation among rows of copper atoms is enough to ‘trap’ the molecule and to create the necessary torque to roll it. Other surface orientations ([111] and [100]) are too smooth and cannot provide the necessary torque for the rolling process.