Jun Harada 교수

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTX-ray Analysis of Structural Changes in Photochromic Salicylideneaniline Crystals. Solid-State Reaction Induced by Two-Photon ExcitationJun Harada, Hidehiro Uekusa, and Yuji OhashiView Author Information CREST Japan Science and Technology Corporation (JST) Department of Chemistry, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku Tokyo 152-8551, Japan Cite this: J. Am. Chem. Soc. 1999, 121, 24, 5809–5810Publication Date (Web):June 3, 1999P

<div class="htmlview paragraph">A new 2.0 <i>ℓ</i> DOHC 4-valve direct injection (DI) gasoline engine has been developed which features new technologies such as swirl intake ports to produce an optimum swirl in the cylinder by variable controlled swirl control valve, pistons with a concave combustion chamber, and high pressure fuel injection system to provide a fine fuel-air mixture cloud in the combustion chamber. These all help to control fuel-air mixture preparation and flam

This tutorial review introduces pedal motion in crystals, where a pair of benzene rings in a molecule move like the pedals of a bicycle. The pedal motion triggers conformational interconversions, which result in disordered crystal structures. The pedal motion also plays important roles in solid-state reactions. This type of molecular motion occurs in a wide range of compounds, although the detection of the process is difficult in most cases. This review also describes how powerful X-ray diffract

An attempt is made to differentiate between the three previously proposed models of the structure of tetragonal BaTiO3. In the new model, the serious parameter-interaction problem was avoided by the use of both neutron and X-ray diffraction data collected from c-domain single crystals. The result of the refinement gave the displacement of the Ti atom from its cubic position as 0.0135 ± 0.0004 Å; the R value was 0.027 and 0.024 for the neutron and X-ray data respectively. The analysis also showed

Some molecules that have a molecular skeleton similar to stilbenes and azobenzenes are known to show an orientational disorder in the crystals. Some of the disorders are known to be dynamic and mediated by a pedal motion in crystals. Dynamic processes of (E)-stilbene (1) and (E)-3,3',4,4'-tetramethylazobenzene (2) in the crystals were investigated by X-ray diffraction analyses. The dynamic disorder and the pedal motion were detected at higher temperature, even in the molecules that showed no tra

Crystal structures of ( E )-azobenzene (1), ( E )-2,2′- dimethylazobenzene (2), ( E )-3,3′-dimethylazobenzene (3) and ( E )-4,4′-dimethylazobenzene (4) were determined by X-ray diffraction at various temperatures. An apparent shrinkage of the N=N bond and its temperature dependence were observed and are interpreted in terms of an artifact caused by the torsional vibration of the N—Ph bonds in crystals. In the crystal structures of (1), (3) and (4) the dynamic disorder was observed. The disorder

Molecular ferroelectric crystals have attracted growing interest as potential alternatives to conventional lead-based ceramic ferroelectrics. We have recently discovered that a class of compounds known as plastic crystals can show multiaxial ferroelectricity, which allows ferroelectric performance even in polycrystalline forms. Here, we report new plastic/ferroelectric ionic molecular crystals that exhibit remarkably small coercive electric fields at room temperature. The easily switchable ferro

Plastic crystals represent a unique compound class that is often encountered in molecules with globular structures. The highly symmetric cubic crystal structure of plastic crystals endows these materials with multiaxial ferroelectricity that allows a three-dimensional realignment of the polarization axes of the crystals, which cannot be achieved using conventional molecular ferroelectric crystals with low crystal symmetry. In this work, we focused our attention on malleability as another charact

Some molecules with a molecular skeleton similar to that of stilbenes and azobenzenes show orientational disorder in the crystals. If the disorder is dynamic, a conformational interconversion takes place through a pedal motion. In this study X-ray diffraction analyses of (E)-stilbene (1) and azobenzene (2) were carried out at various temperatures. We succeeded in observing thermodynamic nonequilibrium states that were generated by fast freezing of the conformational interconversion at low temper

Molecules in crystals often suffer from severe limitations on their dynamic processes, especially on those involving large structural changes. Crystalline compounds, therefore, usually fail to realize their potential as dielectric materials even when they have large dipole moments. To enable polar molecules to undergo dynamic processes and to provide their crystals with dielectric properties, weakly bound charge-transfer (CT) complex crystals have been exploited as a molecular architecture where

The thermochromism of salicylideneanilines in the solid state has been so far explained only in terms of the temperature-induced change of light absorption, which is caused by the shift of the tautomeric equilibrium between the enol and cis-keto forms. In this study, we measured variable temperature diffuse reflectance and fluorescence spectra of the crystalline powders of salicylideneanilines. We also determined their fluorescence quantum yields. The chromaticity coordinates at each temperature

In this study we have revealed that spiropyrans and spirooxazines, which have long been believed to be non-photochromic in the solid state, are generally photochromic in the solid state at least at low temperatures and that their photoreactivity increases greatly as the temperature is lowered.

Although most fulgides show their photochromism in the solid state, crystal structure changes accompanying the photochromism have not been previously observed. The photochromic reactions have been so far considered to take place on surfaces or at defects of the crystals or to proceed with destruction of the crystals. In this study we have succeeded in observing crystal structure changes accompanying the photochromism of fulgides using X-ray diffraction analysis. Detection of the photoproducts in

Plastic crystals are a class of compounds composed of small molecules with globular structures. Plastic crystals exhibit various unique features, most of which arise from the rotator motion and orientational disorder of the constituent molecules. We recently discovered that some plastic crystals exhibit ferroelectricity in lower-temperature phases, including the room-temperature phase. The crystals, i.e., plastic/ferroelectric molecular crystals, have demonstrated several unique features that di