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251.
Hexadecanaphthalenes (S,S,S,S,S,S,S,S,S,S,S,S,S,S,S)-4b and (S,S,S,S,S,S,S,R,S,S,S,S,S,S,S)-4b that possess two tetraphenylporphyrins (TPP) on the upper and lower naphthalene rings were synthesized. Long-range exciton-coupled CD in the Soret region of TPP (about 66 A) was observed. [structure: see text] 相似文献
252.
253.
Mohamed Ismail Awad Mahmoud M. Saleh Takeo Ohsaka 《Journal of Solid State Electrochemistry》2008,12(3):251-258
A rotating cylinder porous electrode (RCPE) of reticulated vitreous carbon (RVC) matrix was used for oxygen reduction reaction
(ORR) in H2SO4 solutions. Cyclic voltammetry and hydrodynamic voltammetric techniques were used for electrochemical characterization of
the ORR. Cyclic voltammograms in stationary solutions showed better performance of the anodically oxidized RVC (for periods
of 1 and 5 min) for the ORR than the untreated RVC in which the first scan (ORR) after the surface treatment was of no utility,
and the second scan was presented here. The hydrodynamic voltammograms obtained at the treated RCPE gave well-defined limiting
current plateau with positively shifted onset potential as compared with the untreated (plain) RVC electrode. The analysis
of the limiting current data on RCPE and the determination of a limiting current enhancement factor α enabled us to quantify the enhancement extent exerted by the anodic oxidation treatment. An enhancement factor of up to ∼3
was obtained at the RCPE electrode anodically oxidized for 5 min. It was found that the α slightly decreased with the rotation speed depending on the extent of anodic oxidation of RVC. This was attributed to the
different mode of mass transfer (diffusion) to the interior of the micropores with different microstructure resulting from
different extent of anodic oxidation. X-ray photoelectron spectroscopic and scanning electron microscopic measurements helped
us to characterize the anodically oxidized RVC surface. 相似文献
254.
Yumiko Naka Lisa Nagashima Hiromu Takayama Khoa Van Le Takeo Sasaki 《Liquid crystals》2020,47(8):1139-1144
ABSTRACT The breath-figure method using the condensation of water droplets can easily fabricate regular porous films. Although the method is simple, the phenomenon itself requires the control of many parameters that change throughout the process. Therefore, we require a unified understanding of polymers for the fabrication of ordered porous films. In this study, to clarify the required molecular structures of polymers to form a regular porous structure, we systematically explored poly(methacrylate)s with cyanobiphenyl moieties connected by dodecyl groups in the side chain (P11CB); these could form a hexagonal ordered porous structure on the entire film surface. The comparison of P11CB and P11B, which is a P11CB without cyano groups, showed that the local polar groups in hydrophobic polymers promote the formation of ordered porous films. Furthermore, no holes were formed in films of P0CB which is a P11CB without alkyl spacers due to its hydrophilicity. Long alkyl chains resulted in changed hydrophilic polymers to hydrophobic polymers. The introduction of long alkyl chains as a spacer between the biphenyl moiety and polymer backbone is preferred in the cases of particularly few amounts of biphenyl groups in the polymer. The biphenyl groups showed the ability to improve film formability. 相似文献
255.
In the presence of the Trost ligands-Pd catalysts, N-monoallylation of bis(2,4,6-triisopropylbenzne)sulfonylamides derived from meso-1,2-diamines proceeds with good to excellent enantioselectivity (85-96% ee) to give asymmetric desymmetrization products. Under the same conditions, in the reaction with meso-bistolunesulfonylamide derivatives, reversal of the enantioselectivity is observed. 相似文献
256.
Takeo Fukunaga Setsuo Kashino Hiroyuki Ishida 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(10):o718-o722
Tartronic acid forms a hydrogen‐bonded complex, C5H5NO·C3H4O5, (I), with 2‐pyridone, while it forms acid salts, namely 3‐hydroxypyridinium hydrogen tartronate, (II), and 4‐hydroxypyridinium hydrogen tartronate, (III), both C5H6NO+·C3H3O5−, with 3‐hydroxypyridine and 4‐hydroxypyridine, respectively. In (I), the pyridone molecules and the acid molecules form R(8) and R(10) hydrogen‐bonded rings, respectively, around the inversion centres. In (II) and (III), the cations and anions are linked by N—H⋯O and O—H⋯O hydrogen bonds to form a hydrogen‐bonded chain. In each of (I), (II) and (III), an intermolecular hydrogen bond is formed between a carboxyl group and the hydroxyl group attached to the central C atom, and in (I), the hydroxyl group participates in an intramolecular hydrogen bond with a carbonyl group. No intermolecular hydrogen bond is formed between the carboxyl groups in (I), or between the carboxyl and carboxylate groups in (II) and (III). 相似文献
257.
Takeo Sasaki Takayuki Kondo Motoki Noro Kazuya Saida Hiroaki Yaguchi Yumiko Naka 《Journal of polymer science. Part A, Polymer chemistry》2012,50(8):1462-1468
Photoinduced depolymerization of poly(olefin sulfone)s mixed with a photobase generating compound was investigated. Irradiation of 254 nm UV light to films comprising of a mixture of a photobase generating compound and poly(olefin sulfone)s with volatile monomers caused photoinduced depolymerization and the irradiated part of the film vaporized. The effect of the poly(olefin sulfone) structure on the photoinduced depolymerization process was investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
258.
Kanda M Sasamoto T Takeba K Hayashi H Kusano T Matsushima Y Nakajima T Kanai S Takano I 《Journal of AOAC International》2012,95(3):923-931
We developed a rapid and efficient means of determining residues of four nitroimidazoles-i.e., dimetridazole, ipronidazole, metronidazole, and ronidazole-and three hydrophilic metabolites- i.e., 2-hydroxymethyl-1-methyl-5-nitroimidazole, 1 -methyl-2-(2'-hydroxyisopropyl)-5-nitroimidazole, and 1-(2-hydroxyethyl)-2-hydroxymethyl-nitroimidazole--in honey. We applied a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) procedure improved to suit a nitroimidazole analysis, which is fast (approximately 30 min) and uses less organic solvent. The procedure involves initial single-phase extraction of 5 g of honey with acetonitrile containing 1% acetic acid, followed by liquid-liquid partitioning involving the addition of 5 g sodium chloride, 1.5 g trisodium citrate dihydrate, and 4 g magnesium sulfate. Moreover, matrix from honey was reduced by an SPE method with an alumina-N cartridge. The samples were analyzed using LC/MS/MS. Chromatographic separation of these nitroimidazoles and metabolites was performed in the gradient mode on a pentafluorophenylpropyl-bonded silica column (150x2.0 mm, 3 pm particle size) at 40 degrees C. The mobile phase consisted of a 0.01% acetic acid solution and acetonitrile, and the flow rate was 0.2 mL/min. The method was validated using honey spiked with these nitroimidazoles from 0.1 to 0.5 microg/kg. The overall recovery of the seven nitroimidazoles ranged from 76.1 to 98.5%; intra- and interassay CV values were <9.5 and <14.2%, respectively. The LOQ ranged from 0.1 to 0.5 microg/kg. LC/MS/MS coupled with the QuEChERS method showed good potential as a method for determining nitroimidazole residues in honey. 相似文献
259.
Ohno H Oyabu I Iizuka Y Hondoh T Narita H Nagao J 《The journal of physical chemistry. A》2011,115(32):8889-8894
The dissociation of C(2)H(6) hydrate particles by slow depressurization at temperatures slightly below the ice melting point was studied using optical microscopy and Raman spectroscopy. Visual observations and Raman measurements revealed that ethane hydrates can be present as a metastable state at pressures lower than the dissociation pressures of the three components: ice, hydrate, and free gas. However, they decompose into liquid water and gas phases once the system pressure drops to the equilibrium boundary for supercooled water, hydrate, and free gas. Structural analyses of obtained Raman spectra indicate that structures of the metastable hydrates and liquid water from the hydrate decay are fundamentally identical to those of the stable hydrates and supercooled water without experience of the hydration. These results imply a considerably high energy barrier for the direct hydrate-to-ice transition. Water solidification, probably induced by dynamic nucleation, was also observed during melting. 相似文献
260.
A new [X+2+Y]-type for the convergent synthesis of polycyclic ethers based on an oxiranyl anion strategy was developed. The sequence involves nucleophilic substitution of a triflate with an oxiranyl anion followed by 6-endo cyclization, ring expansion, and reductive etherification. The protocol features a flexible approach toward trans-fused polycyclic arrays consisting of six- and seven-membered ether rings from the same starting materials. 相似文献