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.

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The propagation of light in a spherically symmetric dust distribution is investigated. A sufficient condition for light to escape from a collapsing region to an expanding region of the system is obtained. This corrects the 1966 result of Raychaudhuri. It is also shown that, contrary to the conclusion drawn by Soin in 1968, no event-horizon other than that associated with the Schwarzschild radius occurs. These results are illustrated by some numerical calculations for particular models.

Calcium ion (Ca 2z ) and crown ethers, 12-crown-4, 15-crown-5, 1-aza-18-crown-6 (A18-crown-6) and 1,10diaza-18-crown-6 (DA18-crown-6), were assembled into divalent supramolecular cation (SC 2z ) structures in the monovalent [Ni(dmit) 2 ] 2 salts (dmit 22 ~2-thioxo-1,3-dithiole-4,5-dithiolate), which regulate the arrangement of the [Ni(dmit) 2 ] 2 anions in the crystal. The divalent SC 2z -[Ni(dmit) 2 ] 2 system showed a larger diversity of crystal structures compared with the monovalent SC z system. Peculiar magnetic behavior was observed depending on the arrangement of the S~1 2 spins on the [Ni(dmit) 2 ] 2 anions. Single crystals of Ca 2z (12-crown-4) 2 [Ni(dmit) 2 ] 2 (1) and Ca 2z (15-crown-5) 2 [Ni(dmit) 2 ] 2 (CH 3 CN) 0.7 (2) had a typical sandwich-type Ca 2z (crown ether) 2 structure, which included the formation of p-p dimers and monomers of [Ni(dmit) 2 ] 2 anions in the crystal. The temperature-dependent magnetic susceptibility (x m ) of salt 1 showed a magnetic transition at 190 K, at which temperature the spins on each [Ni(dmit) 2 ] 2 dimer formed a singlet pair. On the other hand, the magnetic behavior of salt 2 obeyed the Curie-Weiss law. The Ca 2z ions in the isostructural single crystals of Ca 2z (A18-crown-6)[Ni(dmit) 2 ] 2 (CH 3 CN) 2 (3) and Ca 2z (DA18-crown-6)[Ni(dmit) 2 ] 2 (CH 3 CN) 2 (4) were completely included into the 18-crown-6 cavity, and further interacted with two CH 3 CN molecules from the axial position. The resultant Ca 2z (18-crown-6)(CH 3 CN) 2 cations induced the formation of uniform zig-zag chains of the [Ni(dmit) 2 ] 2 anions, the magnetic susceptibility of which were explained by a one-dimensional Heisenberg antiferromagnetic linear chain. The magnetism of these salts was discussed in terms of the intermolecular transfer integral t.