Impact of solvation on the photoisomerisation dynamics of a photon-only rotary molecular motor

Abstract Multiscale nonadiabatic molecular dynamics simulations of the working cycle of a 2-stroke photon-only light-driven molecular rotary motor are presented. The simulations, which produced data consistent with the available transient spectroscopy measurements, predict a considerable decrease in the isomerisation quantum yield in methanol solution with respect to the gas-phase. The origin of the decrease is traced back to the ability of the motor to establish hydrogen bonds with solvent molecules. The analysis suggests that a modified motor molecule with a reduced ability to form hydrogen bonds will display increased quantum efficiency. The results obtained in the present work help to extend the set of engineering rules for designing light-driven molecular rotary motors.