Hovering and Twirling of Tethered Molecules by Confinement between Surfaces
Laura Rios1, Joonhee Lee1, Nicholas Tallarida1
1Department of Chemistry, University of California, Irvine , Irvine, California 92697, United States.
Abstract:
Through STM images, we show that azobenzene-terminated alkanethiols hover and twirl when confined between the Ag tip and Au(111) substrate of an STM junction. In contrast with mechanisms of activation used to drive molecular rotors, twirling is induced by the effective elimination of lateral corrugation in the energy landscape when molecules hover by their van der Waals attraction to the approaching tip. While in the stationary state the benzenes of the head group lie flat with an inter-ring separation of 7.5 Å, they stand on-edge as the molecule twirls and their separation contracts to 5.2 Å, close to the value of the free molecule. The captured images of motion allow the characterization of physisorption potentials.
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