Nineteen cholesterol derivatives containing a variety of azobenzene moieties coupled to C-3 of a steroidal moiety through an ester linkage were synthesized. We employed two different esterification methods by which cholesterol derivatives with the natural (.^-configuration at C-3 and those with the inverted (/^-configuration at C-3 were obtained (the latter derivatives are indicated by a prime). Among them, cholesterol derivatives bearing a p-alkoxyazobenzene moiety (2R and 2R') acted as excellent thermally-reversible gelators of various organic fluids, but the gelation ability is fairly different between 2R and 2R': 2R could gelatinize hydrocarbons such as n-hexane, n-octane, and toluene, halogen solvents such as 1,2-dichloroethane and dichloromethane, ether solvents such as diethyl ether and THF, and alcohols such as ethanol and 1-butanol whereas 2R' could gelatinize ketones, methanol, and polysiloxanes. In general, the solubility of 2R' in apolar solvents is superior to that of 2R, so 2R is useful for gelation of apolar solvents whereas 2R' is useful for gelation of polar solvents. We found that the sol-gel phase transition is sensitively "read-out" by a change in the circular dichroism (CD) spectrum: the gel phase is CD-active whereas the sol phase is totally CD-silent. For example, the 2Me-l-butanol gel gave a positive exciton coupling band with (R)-chirality whereas the 2EFmethanol gel gave a negative exciton coupling band with (5)-chirality. These results mean that dipoles in the azobenzene moiety are oriented in a clockwise (in (R)-chirality) or anticlockwise (in (5")-chirality) direction when they interact in the excited state. Strangely, we accidentally found that the CD sign of the gels prepared from 2Pr, 2Bu, and 3Me? (azobenzene-linked cholesterol derivative with p-NMe2) is frequently inverted. After careful examination of the gel preparation conditions, we found that inversion takes place only when the cooling speed is fast. The scanning electron microscopic studies established that gelators form three-dimensional networks with helical fibrils. Interestingly, we found that in the 3Me' gel prepared from cyclohexane the gel with (R)-chirality in CD possesses a right-handed helix whereas the gel with (S)-chirality in the CD possesses a left-handed helix. The sol-gel phase transition was also induced by photoresponsive cis-trans isomerism of the azobenzene moiety: the gel formed from the franr-isomer was efficiently converted to the sol when trans-to-cis isomerization was photochemically induced, and this process can be repeated reversibly. The photoinduced sol-gel phase transition was also "read-out" as a change in CD spectroscopy.

The gram-order of fullerene (C60) with 99.8 wt% purity was isolated from carbon soot by fractional precipitation with 5,11,17,23,29,35,41,47-octa-tert-butylcalix[8]arene-49,50,51,52,53,54,55,56-octol. This is a very convenient and efficient C60 purification method without any precious apparatus.

A mild, general, and functional group tolerant intramolecular hydroalkoxylation and hydroacyloxylation of unactivated olefins using a Co(salen) complex, an N-fluoropyridinium salt, and a disiloxane reagent is described. This reaction was carried out at room temperature and afforded five- and six-membered oxygen heterocyclic compounds, such as cyclic ethers and lactones. The Co complex was optimized for previously rare medium ring formation by hydrofunctionalization of unactivated olefins. The powerful Co catalyst system also enables the deprotective hydroalkoxylation of O-protected alkenyl alcohol and hydroacyloxylation of alkenyl ester to afford cyclic ethers and lactones directly. The substrate scope and mechanistic proof of deprotection were investigated. The experimental evidence supports the concerted transition state of the bond-forming step involving a cationic Co complex.

By diminishing the energy barrier between SC; and SC*, antiferroelectricity has become thresholdless in a threecomponent mixture. It shows V-shaped switching, realizing attractive display characteristics: extremely wide viewing angle with very large contrast ratio, high speed response and ideal analogue grey scale with no hysteresis. A simplified model of the phase with this property is presented.

We report mechanochromic color change controlled by conformational change (folded and twisted conformers) of fluorenylidene-acridanes (FAs).

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The reactivity of ylide-like phosphasilene 1 [LSi(TMS)═P(TMS), L = PhC(NtBu)2] with group 10 d(10) transition metals is reported. For the first time, a reaction of a phosphasilene with a transition metal that actually involves the silicon-phosphorus double bond was found. In the reaction of 1 with ethylene bis(triphenylphosphine) platinum(0), a complete silicon-phosphorus bond breakage occurs, yielding the unprecedented dinuclear platinum complex 3 [LSi{Pt(PPh3)}2P(TMS)2]. Spectroscopic, structural, and theoretical analysis of complex 3 revealed the cationic silylene (silyliumylidene) character of the silicon unit in complex 3. Similarly, formation of the analogous dinuclear palladium complex 4 [LSi{Pd(PPh3)}2P(TMS)2] from tetrakis(triphenylphosphine) palladium(0) was observed. On the other hand, in the case of bis(cyclooctadiene) nickel(0) as starting material, a distinctively different product, the bis(silylene) nickel complex 5 [{(LSi)2P(TMS)}Ni(COD)], was obtained. Complex 5 was fully characterized including X-ray diffraction analysis. Density functional theory calculations of the reaction mechanisms showed that the migration of the TMS group in the case of platinum and palladium was induced by the oxidative addition of the transition metal into the silicon-silicon bond. The respective platinum intermediate 2 [LSi{Pt(TMS)(PPh3)}P(TMS)] was also experimentally observed. This is contrasted by the reaction of nickel, in which the equilibrium of phosphasilene 1 and the phosphinosilylene 6 [LSiP(TMS)2] was utilized for a better coordination of the silicon(II) moiety in comparison with phosphorus to the transition metal center.