Interruption of the inner rotation initiated in isolated electron-driven molecular rotors

Abstract

An anthracene molecule substituted at the central ring by two aniline moieties able to rotate about the C-N bonds can be considered to be a prototype molecular rotor. Electron attachment into the lowest empty orbitals of this molecule leads to formation of long-lived (microseconds) negative ions. Elimination of a hydrogen molecule from these anions was observed in the gas phase by means of dissociative electron attachment spectroscopy. The experimental findings were interpreted using density functional theory calculations. It was shown that the decay process must be accompanied by formation of a new covalent bond in which one aniline moiety is fixed to the adjacent carbon atom of the anthracene ring. The observed irreversible interruption of the rotational motion could occur in other artificial electron-driven molecular machines provided that suitable atoms approach each other under the rotation.