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Ferroelectricity and polarity control in solid-state flip-flop supramolecular rotators


Molecular rotation has attracted much attention with respect to the development of artificial molecular motors, in an attempt to mimic the intelligent and useful functions of biological molecular motors. Random motion of molecular rotators—for example the 180 flip-flop motion of a rotatory unit—causes a rotation of the local structure. Here, we show that such motion is controllable using an external electric field and demonstrate how such molecular rotators can be used as polarization rotation units in ferroelectric molecules. In particular, m-fluoroanilinium forms a hydrogen-bonding assembly with dibenzo[18]crown-6, which was introduced as the counter cation of [Ni(dmit)2] anions (dmit2−=2-thioxo-1,3-dithiole-4,5-dithiolate). The supramolecular rotator of m-fluoroanilinium exhibited dipole rotation by the application of an electric field, and the crystal showed a ferroelectric transition at 348 K. These findings will open up new strategies for ferroelectric molecules where a chemically designed dipole unit enables control of the nature of the ferroelectric transition temperature.

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Figure 1: Crystal structure and molar magnetic susceptibility (χmol) of (m-FAni+)(DB[18]crown-6) [Ni(dmit)2] (salt 1).
Figure 2: Dielectric properties of salts 1 and 2.
Figure 3: Molecular rotation of the m-FAni+ cation in salt 1.
Figure 4: Average structure of (m-FAni+)(DB[18]crown-6) in salt 1.


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This work was supported in part by a Grant-in-Aid for Science Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. We would like to thank J. Kawamata and H. Yamaki (Yamaguchi Univ.) for conducting the second harmonic generation measurements.

Author information




T.A. and T.N. planned the project and carried out experimental work with the other authors. H.K., D.S. and S.-I.N. carried out sample preparation, structural analysis and electrical measurements. S.T. conducted measurements of temperature-dependent NMR spectra. R.K., H.T. and Y.T. carried out the synchrotron radiation X-ray crystal structural analysis at the High Energy Accelerator Research Organization.

Corresponding authors

Correspondence to Tomoyuki Akutagawa or Takayoshi Nakamura.

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Akutagawa, T., Koshinaka, H., Sato, D. et al. Ferroelectricity and polarity control in solid-state flip-flop supramolecular rotators. Nature Mater 8, 342–347 (2009).

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