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 degree 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 (dmit(2-) = 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.

The quadrupole moment of the 8 B (/* = 2 + , Ti/2=769 msec) nucleus was measured as |(?( 8 B)| = 68.3 ±2.1 mb by use of modified /2-NMR. This value is twice as large as the prediction of the Cohen-Kurath shell model. It is found by subtracting the contribution of deeply bound neutrons that the protons in 8 B carry more than 90% of the observed moment. The anomalous value is accounted for fairly well by the proton halo due to the loosely bound valence configuration. This is the first experimental evidence for the existence of a proton halo covering a neutron core.PACS numbers: 21.10. Ky, 21.10.Ft, 27.20.+n Nuclear properties that depend upon isospin will be enhanced and clearly observed in high isospin states, i.e., in those nuclei located near the proton and neutron drip lines in the mass chart. One of the peculiar observables of those nuclei is the radius of the nuclear matter distribution. For example, from the measurements of interaction cross sections by use of a high-energy nuclear beam of unstable neutron-rich n Li, a neutron halo covering the 9 Li core was found by Tanihata et al. [1]. Regarding the proton halo, however, no signals have been reported yet. It is quite natural to expect such a halo for protons because of the charge symmetry of the nuclear force. However, the Coulomb force among the protons besides the nuclear force may prevent the growth of the halo and push the proton inside the Coulomb barrier. As a result, the proton halo may be less pronounced than the neutron halo even if it is formed. From an experimental point of view, it is difficult to detect the thin halo by such crosssection measurements because the method is mainly designed to observe matter distributions, and therefore the effect due to the proton halo could be only a small fraction of the cross section. For an investigation of the proton halo, on the other hand, quadrupole moments are the most suitable probe, since they reflect dominantly the radial and angular distributions of the valence protons in the case of spherical nuclei. Of specific interest is the quadrupole moment of the 8 B (/ ;r = 2 4 \ T\/2 == 169 msec) nucleus because it is located near the proton drip line. It is expected that the proton distribution swells out radially in this nucleus because the separation energy of one proton is very small, 0.14 MeV, while, on the contrary, that of the neutron is large, 13 MeV. This means that the valence protons are very loosely bound at the shallow ridge of the nuclear potential, while the neutrons are very tightly bound./3-NMR detections [2] are the most promising method to measure the quadrupole moments of 8 B since it is a short-lived f3 emitter. As is well known, however, the detection of the quadrupole effects in the /3-NMR of such unstable nuclei with a nuclear lifetime of about 1 sec is usually very difficult, and time consuming, because of the complexity of the spectral shape and small NMR effect due to its higher spin (7=2 for 8 B), and because of the poor knowledge of the electric field gradients. Therefore, ne...

Nanoscale molecular rotors that can be driven in the solid state have been realized in Cs2([18]crown-6)3[Ni(dmit)2]2 crystals. To provide interactions between the molecular motion of the rotor and the electronic system, [Ni(dmit)2]- ions, which bear one S=1/2 spin on each molecule, were introduced into the crystal. Rotation of the [18]crown-6 molecules within a Cs2([18]crown-6)3 supramolecule above 220 K was confirmed using X-ray diffraction, NMR, and specific heat measurements. Strong correlations were observed between the magnetic behavior of the [Ni(dmit)2]- ions and molecular rotation. Furthermore, braking of the molecular rotation within the crystal was achieved by the application of hydrostatic pressure.

Building a bottom-up supramolecular system to perform continuously autonomous motions will pave the way for the next generation of biomimetic mechanical systems. In biological systems, hierarchical molecular synchronization underlies the generation of spatio-temporal patterns with dissipative structures. However, it remains difficult to build such self-organized working objects via artificial techniques. Herein, we show the first example of a square-wave limit-cycle self-oscillatory motion of a noncovalent assembly of oleic acid and an azobenzene derivative. The assembly steadily flips under continuous blue-light irradiation. Mechanical self-oscillation is established by successively alternating photoisomerization processes and multi-stable phase transitions. These results offer a fundamental strategy for creating a supramolecular motor that works progressively under the operation of molecule-based machines.

Harnessing molecular motion to reversibly control macroscopic properties, such as shape and size, is a fascinating and challenging subject in materials science. Here we design a crystalline cobalt(II) complex with an n-butyl group on its ligands, which exhibits a reversible crystal deformation at a structural phase transition temperature. In the low-temperature phase, the molecular motion of the n-butyl group freezes. On heating, the n-butyl group rotates ca. 100° around the C–C bond resulting in 6–7% expansion of the crystal size along the molecular packing direction. Importantly, crystal deformation is repeatedly observed without breaking the single-crystal state even though the shape change is considerable. Detailed structural analysis allows us to elucidate the underlying mechanism of this deformation. This work may mark a step towards converting the alkyl rotation to the macroscopic deformation in crystalline solids.