A Molecular Rotor Driven by an Electric Field on Graphene.

We propose a scheme for driving a dipolar molecular rotor to rotate continuously by applying an external electric field: the dipolar rotor is fixed on a graphene sheet via a metal atom to facilitate the free rotation; it is in the meantime subjected to an electric field oriented parallel to the graphene sheet. We use computational modeling with density functional theory and Newtonian mechanics, similar to molecular dynamics simulations, to obtain the torque, angular velocity, and rotation period of the rotor. Our results show that the dipolar rotor designed here can rotate with a period of 2.96 ps by an alternating rectangular electric field with a strength of 0.5 V/Å. However, a cosine wave alternating electric field depending on time cannot drive the dipolar rotor to rotate regularly. Therefore, a cosine wave electric field depending on the rotation angle is suggested, as it can not only drive the rotor but also produce additional power. Machine learning molecular dynamics (MLMD) simulations further confirm that the rotor remains thermodynamically stable under an electric field. This work reveals the rotation mechanism of a dipolar molecular rotor in a transverse electric field, and we hope this work can open a new path for designing more diverse molecular machines in experiments.