Centre d’Élaboration de Matériaux et d’Etudes Structurales (UPR 8011)

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Molecular gears

Goal: Intermolecular transfer of rotary motion in a train of single-molecule gears

Staff: Claire Kammerer (Ass. Prof.), Gwénaël Rapenne (Prof.), Jean-Pierre Launay (Emeritus Prof.), Christian Joachim (CNRS Research Director), We-Hyo Soe (Visiting scientist)
Ph.D. students & Postdocs: J. Echeverria (Post-doc), G. Erbland (PhD 2016-19), S. Srivastava (Post-doc), M. Kleinwächter (Post-doc), S. Abid (Post-doc)

The design and synthesis of molecules able to undergo a precise mechanical movement is one of the key towards future molecular mechanical nanomachines.

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Along these lines, we have been able to devise a molecular rack-and-pinion device for which an STM tip drives a single pinion molecule at low temperature. The pinion is a 1.8-nm-diameter molecule functioning as a six-toothed wheel interlocked at the edge of a self-assembled molecular island acting as a rack. The rotation of the pinion molecule tooth by tooth along the rack was monitored by a chemical tag attached to one of its cogs.

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More recently, two of these molecules were mounted each on a single copper adatom separated exactly by 1.9 nm on a lead surface using a low-temperature scanning tunneling microscope (LT-STM). A functioning train of two molecule-gears was constructed complete with a molecule-handle. Not mounted on a Cu adatom axle, this ancillary molecule-gear is mechanically engaged with the first molecule-gear of the train to stabilize its step-by-step rotation. Centered on its Cu adatom axle, the rotation of the first gear of the train step by step rotates the second similar to a train of macroscopic gears. From the handle to the first and to this second molecule-gear, the exact positioning of the two Cu adatom axles on the lead surface ensures that the molecular teeth-to-teeth mechanics is fully reversible. 


In an alternative approach, it is also envisioned to exploit a metallo-organic axle as a way to anchor cogwheels and build trains of molecular gears to ultimately achieve controlled intermolecular gearing motion. The design and synthesis of two families of ruthenium-based molecular-gear prototypes was recently reported. These complexes incorporate a hydrotris(indazolyl)borate moiety as tripodal rotation axle and a pentaarylcyclopentadienyl ligand as star-shaped cogwheel, equipped with five teeth ranging from pseudo-1D aryl groups to large planar 2D paddles. A divergent synthetic approach was followed, starting from a pentakis(p-bromophenyl)cyclopentadienyl ruthenium(II) complex as key precursor or from its iodinated counterpart. Fivefold cross-coupling reactions with various partners allowed high structural diversity to be reached and yielded molecular-gear prototypes with aryl-, carbazole-, BODIPY- and porphyrin-derived teeth of increasing size and length.

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Selected publications

[1] A rack and pinion device at the molecular scale
F. Chiaravalloti, L. Gross, K.-H. Rieder, S. M. Stojkovic, A. Gourdon, C. Joachim, F. Moresco Nature Mater. 2007, 6, 30–33. Download

[2] Step by step rotation of a molecule-gear mounted on an atomic scale axis
C. Manzano, W. -H. Soe, H. S. J. Wong, F. Ample, A. Gourdon, N. Chandrasekhar, C. Joachim Nature Mater. 2009, 8, 576-579. Download

[3] Train of Single Molecule-Gears
W.-H. Soe, S. Srivastava, C. Joachim, J. Phys. Chem. Lett. 2019, 10, 6462−6467. Download

[4] Star-shaped ruthenium complexes as prototypes of molecular gears
G. Erbland, S. Abid, Y. Gisbert, N. Saffon-Merceron, Y. Hashimoto, L. Andreoni, T. Guérin, C. Kammerer, G. Rapenne, Chem. Eur. J. 2019, 25, in press. Download

[5] Biomimetic and technomimetic single molecular machines 
C. Kammerer, G. Erbland, Y. Gisbert, T. Nishino, K. Yasuhara, G. Rapenne, Chem. Lett. 201948, 299-308. Download Couverture