Activating a light-driven molecular motor by metal complexation

Designing increasingly complex, responsive, and dynamic molecular systems, whose actions can be controlled by a combination of cooperative stimuli, is a key challenge toward the development of more advanced functional molecular machines. Herein, we report new photochemically driven molecular motors based on a bis(benzoxazole) ligand. Coordination of the ligand to a metal salt leads to the selective in situ activation of a well-defined motor function, which can be deactivated in the presence of a competing ligand. The rotation speed and absorption wavelength are tuned by the choice of metal, allowing unprecedented control of the molecular system. DFT calculations show that the geometry of the metal center influences the rotational barriers and the possibility to couple the rotary motion with the wagging movement at the metal center. The approach presented here will open new avenues toward more complex, dynamic, and coupled systems.