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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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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Manzano, C., Soe, WH., Wong, H. et al. Step-by-step rotation of a molecule-gear mounted on an atomic-scale axis. Nature Mater 8, 576–579 (2009). https://doi.org/10.1038/nmat2467