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101.
Enomoto T Kanematsu S Tsunashima K Matsumoto K Hagiwara R 《Physical chemistry chemical physics : PCCP》2011,13(27):12536-12544
Fluorohydrogenate salts of quaternary phosphonium cations with alkyl and methoxy groups (tetraethylphosphonium (P(2222)(+)), triethyl-n-pentylphosphonium (P(2225)(+)), triethyl-n-octylphosphonium (P(2228)(+)), and triethylmethoxymethylphosphonium (P(222(101))(+))) have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium bromide or chloride precursors. The three salts with asymmetric cations, P(222m)(FH)(2.1)F (m = 5, 8, and 101), are room temperature ionic liquids (ILs) and are characterized by differential scanning calorimetry, density, viscosity, and conductivity measurements. Linear sweep voltammetry using a glassy carbon working electrode shows these phosphonium fluorohydrogenate ILs have wide electrochemical windows (>4.9 V) with the lowest viscosity and highest conductivity in the known phosphonium-based ILs. Thermogravimetry shows their thermal stabilities are also improved compared to previously reported alkylammonium cation-based fluorohydrogenate salts. Differential scanning calorimetry and X-ray diffraction revealed that tetraethylphosphonium fluorohydrogenate salt, P(2222)(FH)(2)F, exhibits two plastic crystal phases. The high temperature phase has a hexagonal lattice, which is the first example of a plastic crystal phase with an inverse nickel arsenide-type structure, and the low-temperature phase has an orthorhombic lattice. The high-temperature plastic crystal phase exhibits a conductivity of 5 mS cm(-1) at 50 °C, which is the highest value for the neat plastic crystals. 相似文献
102.
Aramburo LR Karwacki L Cubillas P Asahina S de Winter DA Drury MR Buurmans IL Stavitski E Mores D Daturi M Bazin P Dumas P Thibault-Starzyk F Post JA Anderson MW Terasaki O Weckhuysen BM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(49):13773-13781
A combination of atomic force microscopy (AFM), high‐resolution scanning electron microscopy (HR‐SEM), focused‐ion‐beam scanning electron microscopy (FIB‐SEM), X‐ray photoelectron spectroscopy (XPS), confocal fluorescence microscopy (CFM), and UV/Vis and synchrotron‐based IR microspectroscopy was used to investigate the dealumination processes of zeolite ZSM‐5 at the individual crystal level. It was shown that steaming has a significant impact on the porosity, acidity, and reactivity of the zeolite materials. The catalytic performance, tested by the styrene oligomerization and methanol‐to‐olefin reactions, led to the conclusion that mild steaming conditions resulted in greatly enhanced acidity and reactivity of dealuminated zeolite ZSM‐5. Interestingly, only residual surface mesoporosity was generated in the mildly steamed ZSM‐5 zeolite, leading to rapid crystal coloration and coking upon catalytic testing and indicating an enhanced deactivation of the zeolites. In contrast, harsh steaming conditions generated 5–50 nm mesopores, extensively improving the accessibility of the zeolites. However, severe dealumination decreased the strength of the Brønsted acid sites, causing a depletion of the overall acidity, which resulted in a major drop in catalytic activity. 相似文献
103.
Shunsuke Kotani Masaya Ito Hirono Nozaki Masaharu Sugiura Masamichi Ogasawara Makoto Nakajima 《Tetrahedron letters》2013
An application of a hypervalent silicon complex, generated from a chiral phosphine oxide catalyst and silicon tetrachloride, to the enantioselective organocatalytic Morita–Baylis–Hillman reaction is described. A chloride anion liberated from the hypervalent silicon complex smoothly generated a γ-chloro silyl enol ether that subsequently reacted with an aldehyde to afford the Baylis–Hillman adducts in good yields and with good enantioselectivities. 相似文献
104.
K. Norisuye K. Okamura Y. Sohrin H. Hasegawa T. Nakanishi 《Journal of Radioanalytical and Nuclear Chemistry》2005,267(1):183-193
Summary The present paper describes a new analytical method for determining the 240Pu/239Pu isotopic ratio and 238Pu/239+240Pu α -activity ratio in seawater, both of which are important parameters for determining Pu sources in the ocean. Plutonium
isotopes were preconcentrated from a large volume of seawater (4700-10800 liter) by solid phase extraction using MnO2-impregnated fibers and eluted into 3M HCl. After the elution, the Pu species of all oxidation states were converted to Pu(IV)
using NaNO2, purified by solvent extraction using thenoyltrifluoroacetone (TTA)-benzene, and concentrated in 5 ml of 0.2M HNO2. The 240Pu/239Pu and 238Pu/239+240Pu ratios in the 5-ml final solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and α-spectrometry,
respectively. A pg level of Pu, which was a sufficiently large amount for the determination, was obtained by the solid phase
extraction. Through the redox conversion and solvent extraction, the Pu species, such as Pu(III), Pu(IV) and Pu(VI), were
collected at a high recovery of 96±2% (n=3) despite the presence of large amounts of Mn, and interfering 238U (3.3 μg. l-1in seawater) was effectively removed with a decontamination factor of 1.7·107. The accuracy of the method for the 240Pu/239Pu ratio was verified using reference materials of seawater and a terrestrial soil sample. The present technique was applied
to the determination of the 240Pu/239Pu and 238Pu/239+240Pu ratios in coastal and oceanic water. 相似文献
105.
The pyridinium bisretinoid A2E, an autofluorescent pigment that accumulates in retinal pigment epithelial cells with age and in some retinal disorders, can mediate a detergent-like perturbation of cell membranes and light-induced damage to the cell. The photodynamic events initiated by the sensitization of A2E include the generation of singlet oxygen and the oxidation of A2E at carbon-carbon double bonds. To assess the ability of plant-derived anthocyanins to modulate adverse effects of A2E accumulation on retinal pigment epithelium (RPE) cells, these flavylium salts were isolated from extracts of bilberry. Nine anthocyanin fractions reflecting monoglycosides of delphinidin, cyanidin, petunidin and malvidin were obtained and all were shown to suppress the photooxidation of A2E at least in part by quenching singlet oxygen. The anthocyanins tested exhibited antioxidant activity of variable efficiency. The structural characteristics relevant to this variability likely included the ability to form a stable quinonoidal anhydro base at neutral pH, a conjugated diene structure in the C (pyrane) ring, the presence of hydroxyl groups on the B (benzene) ring and the relative hydrophobicity conferred by the arrangement of substituents on the B ring. Cells that had taken up anthocyanins also exhibited a resistance to the membrane permeabilization that occurs as a result of the detergent-like action of A2E. 相似文献
106.
ArS(ArSSAr)+ (arylbis(arylthio)sulfonium ions), which were generated and accumulated by the electrochemical oxidation of diaryl disulfides (ArSSAr) in CH2Cl2 at −78 °C, reacted with alkenes to give the corresponding diarylthio-substituted compounds in a stereospecific manner in good yields, when the reaction was quenched with a soft nucleophile, such as allylsilanes, ketene silyl acetals, and triethylamine. A mechanism involving the initial formation of an episulfonium ion followed by ring-opening by the attack of ArSSAr has been suggested. The reactions of ArS(ArSSAr)+ with alkynes also took place to give 1,2-diorganothio-substitued alkenes stereoselectively under similar conditions. 相似文献
107.
Goudappagouda Ananthakrishnan Manthanath Vivek Chandrakant Wakchaure Kayaramkodath Chandran Ranjeesh Tamal Das Kumar Vanka Takashi Nakanishi Sukumaran Santhosh Babu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2306-2310
Organic phosphors have been widely explored with an understanding that crystalline molecular ordering is a requisite for enhanced intersystem crossing. In this context, we explored the room‐temperature phosphorescence features of a solvent‐free organic liquid phosphor in air. While alkyl chain substitution varied the physical states of the bromonaphthalimides, the phosphorescence remained unaltered for the solvent‐free liquid in air. As the first report, a solvent‐free liquid of a long swallow‐tailed bromonaphthalimide exhibits room‐temperature phosphorescence in air. Doping of the phosphor with carbonyl guests resulted in enhanced phosphorescence, and hence a large‐area paintable phosphorescent liquid composite with improved lifetime and quantum yield was developed. 相似文献
108.
Yosuke Hara Kazuyoshi Kanamori Kazuki Nakanishi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19223-19229
We present a two‐step template‐free approach toward monolithic materials with controlled trimodal porous structures with macro‐, meso‐, and micropores. Our method relies on two ordering processes in discrete length scales: 1) Spontaneous formation of macroporous structures in monolithic materials by the sol–gel process through the short‐range ordered self‐assembly of metal–organic frameworks (MOFs), and 2) reorganization of the framework structures in a mediator solution. The Zr‐terephthalate‐based MOF (UiO‐66‐NH2) was adopted as a proof of concept. The self‐assembly‐induced phase separation process offered interconnected macropores with diameters ranging from 0.9 to 1.8 μm. The subsequent reorganization process converted the microporous structure from low crystalline framework to crystalline UiO‐66. The resultant mesopore size within the skeletons was controlled in the range from 9 to 21 nm. This approach provides a novel way of designing spaces from nano‐ to micrometer scale in network‐forming materials. 相似文献
109.
Ikuo Kawashima Hiroaki Imoto Masatoshi Ishida Hiroyuki Furuta Shunsuke Yamamoto Masaya Mitsuishi Susumu Tanaka Toshiki Fujii Kensuke Naka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11812-11816
Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green‐to‐red region (500–700 nm) and the near‐ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S1) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S1 states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S1 states. 相似文献
110.
Tadashi Sasaki Katsumaro Minamoto Toshimichi Suzuki Shunsuke Yamashita 《Tetrahedron》1980,36(7):865-870
In search for a simpler model system for the study of intramolecular thermal reactions between the base and 5'-functionalized sugar moiety in nucleosides, 1-(3-azidopropyl)uracil (2), 1-(4-azidobutyl) pyrimidines (12 and 13) and 1-(5-azidopentyl)-uracil (14) was synthesized through the corresponding ω-benzoyloxy-(6,7 and 8) and ω-hydroxyalkyl-pyrimidines (9,10 and 11). Heating 2 gave 1,N6-trimethylene-6-aminouracil (4), while heating 12 and 13 gave N1-C6 cleaved addition products. 15 and 16, respectively. 15 was regiospecifically transformed to 1,2,3-triazole derivatives, 17,18 and 19. Heating 1-(4-azidobutyl)-5-bromouracil (20) yielded 3,9-tetramethylene-8-azaxanthine (22). 9 with NBA gave 1,06-tetramethylene-5-bromo-6-hydroxy-5,6-dihydrouracil (24) and the 5-brominated analog of 9 (25). The 4-functionalized butyl side chain proved to serve as a substitute for the 5'-functionalized sugar moiety in pyrimidine ribonucleosides. 相似文献