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Mechanical twisting of a guest by a photoresponsive host

Nature volume 440, pages 512515 (23 March 2006) | Download Citation



Molecular analogues of a variety of mechanical devices such as shuttles, brakes, unidirectional rotors and tweezers have been created1,2,3,4,5,6,7,8,9,10,11. But these ‘molecular machines’ have not yet been used to mechanically manipulate a second molecule in a controlled and reversible manner. Here we show that light-induced scissor-like conformational changes of one molecule5 can give rise to mechanical twisting of a non-covalently bound guest molecule. To realize this coupling of molecular motions, we use a previously designed system5: a ferrocene moiety with an azobenzene strap, each end of which is attached to one of the two cyclopentadienyl rings of the ferrocene unit, acts as a pivot so that photoisomerization of the strap rotates the ferrocene rings relative to each other and thereby also changes the relative position of two ‘pedal’ moieties attached to the ferrocene rings. We translate this effect into intermolecular coupling of motion by endowing the pedals with binding sites, which allow the host system to form a stable complex with a bidentate rotor molecule. Using circular dichroism spectroscopy, we show that the photoinduced conformational changes of the host are indeed transmitted and induce mechanical twisting of the rotor molecule. This design concept, which significantly extends the successful coupling of motion beyond the intramolecular level seen in synthetic allosteric receptors12, might allow for the remote control of molecular events in larger interlocked molecular systems.

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T.M. thanks the JSPS Young Scientist Fellowship. This research was partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research on Priority Areas ‘Life-Surveyors’ (to K.K.). We thank Y. Casta and S. Nara for cooperation in synthesis, and N. Tamai and M. Irie for discussion on photophysics.

Author information

Author notes

    • Takahiro Muraoka
    • , Kazushi Kinbara
    •  & Takuzo Aida

    *These authors contributed equally to this work


  1. Department of Chemistry and Biotechnology, School of Engineering, and Centre for NanoBio Integration, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

    • Takahiro Muraoka
    • , Kazushi Kinbara
    •  & Takuzo Aida
  2. PRESTO, Japan Science Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan

    • Kazushi Kinbara


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Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Corresponding authors

Correspondence to Kazushi Kinbara or Takuzo Aida.

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    Supplementary Notes

    This file contains the Supplementary Methods (experimental details for synthesis and measurements) and Supplementary Figures 1-12.


  1. 1.

    Supplementary Movie 1

    This movie represents computer-generated 3D molecular models of 2otrans-1 and 2ocis-1 viewed from various angles.

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