An oscillating molecular turnstile.

An oscillating molecular turnstile based on a stator composed of a porphyrin core bearing two trans coordinating pyridyl units at the meso positions and a rotor equipped with a pyridyl group was designed. Whereas, in solution, the rotor freely rotates around the stator, in the presence of a silver cation behaving as an effector, the system oscillates between two stations. The oscillatory movement may be frozen upon cooling at -70 °C generating thus the closed state of the turnstile. The switching of the system between the open and closed states may be achieved using an external stimulus such as addition of Et(4)NBr.