Step-by-step rotation of a molecule-gear mounted on an atomic-scale axis


Gears are microfabricated down to diameters of a few micrometres. Natural macromolecular motors, of tens of nanometres in diameter, also show gear effects1. At a smaller scale, the random rotation of a single-molecule rotor encaged in a molecular stator has been observed2, demonstrating that a single molecule can be rotated with the tip of a scanning tunnelling microscope3,4 (STM). A self-assembled rack-and-pinion molecular machine where the STM tip apex is the rotation axis of the pinion was also tested5. Here, we present the mechanics of an intentionally constructed molecule-gear on a Au(111) surface, mounting and centring one hexa-t-butyl-pyrimidopentaphenylbenzene molecule on one atom axis. The combination of molecular design, molecular manipulation and surface atomic structure selection leads to the construction of a fundamental component of a planar single-molecule mechanical machine. The rotation of our molecule-gear is step-by-step and totally under control, demonstrating nine stable stations in both directions.

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Figure 1: HB-NBP molecule.
Figure 2: Surface repulsive barrier, HB-NBP versus herringbone ridge.
Figure 3: Molecule-gear construction.
Figure 4: Molecule-gear rotation.


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We acknowledge the Agency for Science Technology and Research (A*STAR) for financial support provided through the Visiting Investigatorship Program (phase I) ‘Atomic Scale Technology Project’.

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C.M. and W.-H.S. were equally responsible for conducting the whole STM experiments, H.S.W. provided support with the experiments, A.G. and C.J. were responsible for the molecular design, A.G. for the chemical synthesis, F.A. and C.J. for the calculations, and N.C. and C.J. were responsible for the interpretation and planning of the experiments.

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Correspondence to C. Manzano or W.-H. Soe.

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Manzano, C., Soe, W., Wong, H. et al. Step-by-step rotation of a molecule-gear mounted on an atomic-scale axis. Nature Mater 8, 576–579 (2009).

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