Light-Driven Molecular Rotors at Surfaces

This project aims to contribute to the rapidly growing field of molecular machines by theoretically and computationally investigating the operation and design of simple molecular rotors in highly-controlled environments, especially when attached to crystalline surfaces in vacuum. The long-range goal is to improve our ability to understand and design effective and useful molecular rotors. We plan to investigate, for small molecules, the fundamental issues of energy flow and control that are necessary to make a rotor useful. Our approach will emphasize underlying physical mechanisms by simulating molecules of minimum complexity which exhibit the required motor behavior under light excitation and which also allow a more complete understanding of their mechanisms. This includes in particular changes in molecular conformation and charge distribution due to energy injection, and energy exchange between the rotation and vibrations of both the molecule and its support. We will study rotor-on-surface systems by means of statistical physics principles, photon excitation mechanisms, first-principles total-energy calculations, phonon analysis, molecular dynamics simulations and surface science methodologies. Our project will theoretically and computationally design and optimize combinations of small rotor molecules and solid surfaces to exhibit and elucidate the underlying governing principles. These systems will also be realistic enough to be subjected to later independent surface science experiments under highly controlled conditions.