Smallest molecular machine: Reversible sliding motion in ammonium-linked ferrocene

Ferrocene is a key molecule for developing molecular machines. However, it readily decomposes on the surface of flat noble metal substrates, marking a significant challenge. Now researchers have stabilized ferrocene by linking it with ammonium salts and trapping them in a molecular film made up of cyclic crown ether molecules. The ammonium-linked molecule performs reversible lateral sliding motion upon the application of electrical voltage, representing the smallest molecular machine.