A simple molecular machine operated by photoinduced proton transfer

The threading-dethreading of a photoinactive pH-switchable calix[6]arene bipyridinium pseudorotaxane in solution has been controlled by visible light irradiation using a merocyanine compound as a photoacid. The coupling between the two molecular switches that communicate with one another by intermolecular proton transfer provides a general principle for the operation of acid-base controllable molecular machines with light.