コヒーレントな分子の協同運動を利用した超分子スイッチ Supramolecular Switching by Coherent Collective Molecular Motion in the Single Crystal of Pseudo-Rotaxane
The single crystal of the pseudorotaxane derivative, which consists of a crown ether and <I>N</I>- (xylyl) aminomethylferrocene derivative shows reversible single crystal-to-single crystal first order phase transition. The transformation brings about change of the optical properties of the crystal; transmittance of polarized light shed on the (001) face is increased and decreased by the change of temperature around the <I>T</I><SUB>c</SUB> (128°C) . At the high temperature phase, the optical anisotropic parameter of birefringence of the crystal is smaller than that at low temperature phase. The connection of the phase transition and the optical property shows potential use of the material as a thermo-optic switch. The thermo-optic switching performance of the crystals is able to be repeated for at least 10 times. Using the newly developed very rapid single crystal diffraction technique, the structures before and after the phase transition have been analyzed. The <I>p</I>-tolyl and phenylene groups are aligned almost perpendicular to the (001) face at the low temperature phase. At the high temperature phase, on the other hand, all the <I>p</I>-tolyl groups of the axle molecules in the crystal rotate at the same direction against the (001) face. The optical switching results from this collective harmonic rotation of the <I>p</I>-tolyl groups.
日本結晶学会誌 50(3), 212-217, 2008-06-30
The Crystallographic Society of Japan