Photochromic acrylates containing both biphenylene and spiro-oxazine moieties with a chiral substituent and the related polymers were prepared and yielded photochromic chiral liquid crystalline systems. The photochromic acrylates containing both an undecamethylene group and a (2S, 3S)-2-chloro-3-methylpentanoyloxy group (A11SOP) or a (-)-menthoxyacetoxy group (A11SOM) gave a supercooled mesophase; the latter reflected right-handed visible light (blue colour) at room temperature. On the other hand, the photochromic acrylate containing both the (R)-(-)-2-methylpropylene and (2S, 3S)-2-chloro-3-methylpentanoyloxy groups (A3SOP) showed no mesophase. The related homopolymers, PA11SOP and PA11SOM, did not exhibit mesophases because of steric hindrance between the side groups of the polymers. However, only PA11SOM exhibited shear-induced birefringence under 100-104°C. Several copolymers consisting of the nematogenic monomer, 4-[4-(6-acryloyloxyhexyloxy)benzoyloxy]benzonitrile (A6CN), and A11SOP or A11SOM possessed a smectic phase due to reduction of the steric hindrance between the potentially smectogenic A11SOP or A11SOM moieties. 相似文献
A flower-inducing compound, LDS1, was isolated from a free-floating aquatic plant, Lemna paucicostata. The chemical structure and the absolute stereochemistry of LDS1 were determined as (9R,13R,11E,15Z)-9,13-dihydroxy-10-oxooctadeca-11,15-dienoic acid for its most abundant diastereomer. LDS1 was enzymatically produced when the plant was exposed to drought stress, and induced flowering at a concentration of 10 nM. 相似文献
Selective oxidation of sulfides to sulfoxides and sulfones with hydrogen peroxide under organic solvent-free conditions was demonstrated by the MWW-type titanosilicate zeolite catalyst. Sulfides were oxidized smoothly to give sulfoxides with good selectivities at ambient temperature using 1.0–1.2 equiv of hydrogen peroxide with the MWW-type titanosilicate zeolite catalyst. Especially, the Ti-MWW with an interlayer-expanded structure (Ti-IEZ-MWW) catalyst showed high activity with good chemoselectivity for the oxidation of various sulfides. The catalyst is recyclable for at least five cycles, and the only byproduct is water. Sulfides were directly oxidized to give sulfones in high yields by 2.5 equiv of hydrogen peroxide with the MWW-type titanosilicate zeolite catalyst under organic solvent-free conditions. 相似文献
Dr Martin Seah, NPL, was the initiator, founder, and first chairman of the Surface Analysis Working Group (SAWG) at the Consultative Committee for Amount of Substance, Metrology in Chemistry and Biology (CCQM) at the Bureau International des Poids et Mesures (BIPM), the international organization established by the Metre Convention. This tribute letter summarizes his achievements during his chairmanship and his long-running impact on the successful work of the group after his retirement. 相似文献
A polymeric multilayered mirror doped with a saturable dye worked as a passive Q-switch of a laser-diode-pumped Nd(3+):YVO4 microchip laser. The multilayered mirror consisted of alternately spin-coated layers of polyvinylcarbazole (PVK) and cellulose acetate on a glass substrate. A dye of bis-(dimethylaminodithiobenzil)-nickel was doped in one of the layers of PVK, providing the repetitively Q-switched pulses. The pulse width and repetition rate were 4 ns and 68 kHz, respectively, for a laser-cavity length of 5 mm, and the average and the peak power were 40 mW and 156 W, respectively, for the highest pump power of 435 mW. The dependence of the Q-switched characteristics on the pump power and on the concentration of the doped dye is described. 相似文献
Cellulose, which comprises D-glucose and L-glucose (D,L-cellulose), was synthesized from D-glucose (1D) and L-glucose (1L) via cationic ring-opening polymerization. Specifically, the ring-opening copolymerization of 3-O-benzyl-2,6-di-O-pivaloyl-β-D-glucopyranoside (2D) and 3-O-benzyl-2,6-di-O-pivaloyl-β-D-glucopyranoside (2L), synthesized from compounds 1D and 1L, respectively, in a 1:1 ratio, afforded 3-O-benzyl-2,6-di-O-β-D,L-glucopyranan (3DL) with a degree of polymerization (DPn) of 28.5 (Mw/Mn?=?1.90) in quantitative yield. The deprotection of compound 3DL and subsequent acetylation proceeded smoothly to afford acetylated compound 4DL with a DPn of 18.6 (Mw/Mn?=?2.08). The specific rotation of acetylated compound 4DL was?+?0.01°, suggesting that acetylated compound 4DL was optically inactive cellulose triacetate. Furthermore, before acetylation, compound 4DL was an optically inactive cellulose comprising an almost racemic mixture of D-glucose and L-glucose. Compound 4DL was an amorphous polymer. This is the first reported synthesis of optically inactive D,L-cellulose.
Ferroelasticity has been reported for several types of molecular crystals, which show mechanical‐stress‐induced shape change under twinning and/or spontaneous formation of strain. Aiming to create materials that exhibit both ferroelasticity and light‐emission characteristics, we discovered the first examples of ferroelastic luminescent organometallic crystals. Crystals of arylgold(I)(N‐heterocyclic carbene)(NHC) complexes bend upon exposure to anisotropic mechanical stress. X‐ray diffraction analyses and stress‐strain measurements on these ferroelastic crystals confirmed typical ferroelastic behavior, mechanical twinning, and the spontaneous build‐up of strain. A comparison with single‐crystal structures of related gold‐NHC complexes that do not show ferroelasticity shed light on the structural origins of the ferroelastic behavior. 相似文献
The iridium-catalyzed allylic alkylation with azlactone and sequential aza-Cope rearrangement was demonstrated. The sequential reaction was effective in separating of diastereoisomers and afforded a diastereomerically pure azlactone derivative and oxazolinone derivative. 相似文献