Non-Adiabatic Dynamics Simulations of a Light-Driven Molecular Motor in Solution

Despite molecular motors have numerous potential applications in optoelectronics, where optical properties can be tuned to transform light into mechanical movements, finding relationships between molecular motion and the environment is challenging. Here, we report the first excited state dynamics study of an overcrowded alkene in solution using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach combined with non-adiabatic molecular dynamics simulations. Using QM/MM surface-hopping trajectories, we calculate time-resolved emission and transient absorption spectra. These show the rise of a short-lived Frank-Condon state in the first 150 fs, followed by a formation of a dark state, before the motor relaxes to the ground state in about 1 ps. From the analysis of radial distribution functions we infer that the orientation of the solvent in the electronic excited state is similar to that in the ground state during the photoisomerization.