Molecular motors are biological molecular machines that convert energy into motion or mechanical work participating in many important processes such as muscle contraction, intracellular cargo transport or transcription of RNA from DNA. Thus, it is natural that these systems serve as an inspiration for chemists on the search for new and more complex synthetic machine-like functions.
In 1999 Feringa and co-workers at the University of Groningen (Netherlands) designed a synthetic molecular rotor, activated by ultraviolet light, capable of performing unidirectional 360o rotation and more recently in 2011 they took the concept one step further by synthesising a light-driven nanocar.
The car composed by a carbazole substituted diphenylbutadiyne chassis and 4 fluorene-based molecular motors acting as wheels can travel as far as 6 nm across a Cu(111) surface in 10 excitation steps. Movement requires that the adsorption energy of the molecule is less than the energy released in the isomerization step upon excitation and each cycle of unidirectional rotation takes 4 reaction steps: 1 double-bond isomerization induced by electronic excitation followed by 1 helix inversion induced by vibrational excitation and again 1 more double-bond isomerization and 1 more helix inversion to complete a 360o rotation.
I can imagine a teenager NanoKid, the kid-shaped organic molecule from the series of Nanoputians, asking his NanoDaddy to buy him the last model of NanoCar capable of running 6 nm in 10 electric bursts. Although, I don’t think NanoMum likes the idea…
Do you want to know more? Then, go directly to the sources:
Nagatoshi Koumura, Robert W. J. Zijlstra, Richard A. van Delden, Nobuyuki Harada, Ben L. Feringa. Light-driven monodirectional molecular rotor. Nature 401, 152-155 (9 September 1999).
Tibor Kudernac, Nopporn Ruangsupapichat, Manfred Parschau, Beatriz Maciá, Nathalie Katsonis, Syuzanna R. Harutyunyan, Karl-Heinz Ernst, Ben L. Feringa. Electrically driven directional motion of a four-wheeled molecule on a metal surface. Nature 479, 208–211 (10 November 2011).