Simulations of optically switchable molecular machines for particle transport

A promising application for design and deployment of molecular machines is nanoscale transport, driven by artificial cilia. In this contribution, we present several further steps toward this goal, beyond our first‐generation artificial cilium (Raeker et al., J. Phys. Chem. A 2012, 116, 11241). Promising new azobenzene‐derivatives were tested for use as cilium motors. Using a QM/MM partitioning in on‐the‐fly photodynamics, excited‐state surface‐hopping trajectories were calculated for each isomerization direction and each motor version. The methods used were reparametrized semiempirical quantum chemistry together with floating‐occupation configuration interaction as the QM part and the OPLSAA‐L forcefield as MM part. In addition, we simulated actual particle transport by a single cilium attached to a model surface, with varying attachment strengths and modes, and with transport targets ranging from single atoms to multi‐molecule arrangements. Our results provide valuable design guidelines for cilia‐driven nanoscale transport and emphasize the need to carefully select the whole setup (not just the cilium itself, but also its surface attachment and the dynamic cilium‐target interaction) to achieve true transport. © 2018 Wiley Periodicals, Inc. Combining semiempirical quantum mechanical methods with force fields in a QM/MM ansatz makes studies of excited‐state dynamics of large molecules possible. Several azobenzene‐based artificial cilia and their dynamical properties are presented. In addition, one system attached to a model surface was used to simulate transport of a single atom up to multi‐molecule arrangements.