Nanocrystallization of oligosilanes by a reprecipitation method: easy fabrication of H-aggregates of linear-chain oligosilane molecules

Nanocrystals of several oligosilanes have been fabricated easily by using a reprecipitation method. The nanocrystals reveal an intense absorption band at the UVB region (280 to 320 nm) and a fluorescence band with large Stokes shift. These photophysical properties show that the nanocrystals exhibit an excitonic interaction of the H-aggregate type.     

Noble metal-free hydrazine fuel cell catalysts: EPOC effect in competing chemical and electrochemical reaction pathways

We report the discovery of a highly active Ni-Co alloy electrocatalyst for the oxidation of hydrazine (N(2)H(4)) and provide evidence for competing electrochemical (faradaic) and chemical (nonfaradaic) reaction pathways. The electrochemical conversion of hydrazine on catalytic surfaces in fuel cells is of great scientific and technological interest, because it offers multiple redox states, complex reaction pathways, and significantly more favorable energy and power densities compared to hydrogen fuel. Structure-reactivity relations of a Ni(60)Co(40) alloy electrocatalyst are presented with a 6-fold increase in catalytic N(2)H(4) oxidation activity over today's benchmark catalysts. We further study the mechanistic pathways of the catalytic N(2)H(4) conversion as function of the applied electrode potential using differentially pumped electrochemical mass spectrometry (DEMS). At positive overpotentials, N(2)H(4) is electrooxidized into nitrogen consuming hydroxide ions, which is the fuel cell-relevant faradaic reaction pathway. In parallel, N(2)H(4) decomposes chemically into molecular nitrogen and hydrogen over a broad range of electrode potentials. The electroless chemical decomposition rate was controlled by the electrode potential, suggesting a rare example of a liquid-phase electrochemical promotion effect of a chemical catalytic reaction ("EPOC"). The coexisting electrocatalytic (faradaic) and heterogeneous catalytic (electroless, nonfaradaic) reaction pathways have important implications for the efficiency of hydrazine fuel cells.     

Determination of the Diameter‐Dependent Onset Potential for the Oxygenation of SWCNTs

The evaluation of the diameter‐dependent onset potential for the oxygenation of a SWCNT (single‐walled carbon nanotube) is an important issue because its chemical and physical properties, such as chemical reactivity, electronic conductance, and optical characteristics, would be changed. We investigated the diameter‐dependent onset potential for the oxygenation of SWCNTs in neutral aqueous solution by using in situ Raman spectroelectrochemical measurements, which was explained quantitatively in terms of the strain energy per carbon atom. These results will be useful for the fabrication of materials in which CNTs are used as a platform for applications such as fuel cells, capacitors, and Li‐ion batteries.     

A Chemical Synthesis of 3-Deoxy-D-manno-2-octulosonic Acid from D-mannose

A chemical synthesis of Kdo was achieved via the condensation of a protected D-mannofuranose-5,6-cyclic sulfate with ethyl 1,3-dithiane-2-carboxylate, which is an efficient equivalent for installing an α-ketoester unit as a key step.     

Chemoselective Catalytic Asymmetric Synthesis of Functionalized Aminals Through the Umpolung Organocascade Reaction of α‐Imino Amides

Chiral functionalized aminals are important core structures of natural products and pharmaceuticals. Their chemo‐ and regioselective catalytic, asymmetric synthesis has been realized through the umpolung reaction of α‐imino amides using a catalyst we originally developed. Functionalized aminals were prepared with high chemoselectivity by treating a hemiaminal intermediate with pyridine in butanol. Evaluation of substrate scope revealed that this transformation could be achieved with a wide range of α‐imino amides to produce the desired products in high yields with up to 97 % ee. A mechanistic study suggested that aminal formation proceeded through the ring opening/ring closing equilibrium of the hemiaminal skeleton.     

Development of novel magnetic nano-carriers for high-performance affinity purification

We developed novel magnetic nano-carriers around 180 nm in diameter for affinity purification. Prepared magnetic nano-carriers possessed uniform core/shell/shell nano-structure composed of 40 nm magnetite particles/poly(styrene-co-glycidyl methacrylate (GMA))/polyGMA, which was constructed by admicellar polymerization. By utilizing relatively large 40 nm magnetite particles with large magnetization, the magnetic nano-carriers could show good response to permanent magnet. Thanks to uniform polymer shell with high physical/chemical stability, the magnetic nano-carriers could disperse in a wide range of organic solvent without disruption of core/shell structure and could immobilize various kinds of drugs. We examined affinity purification using our prepared magnetic nano-carriers with anti-cancer agent methotrexate (MTX) as ligand. Our magnetic nano-carriers showed higher performance compared to commercially available magnetic beads in terms of purification efficiency of target including extent of non-specific binding protein.     

Structure elucidation and NMR spectral assignments of four neolignan glycosides with enantiometric aglycones from Osmanthus ilicifolius

Four new 8-O-4' type neolignan glycosides with enantiometric aglycones, (7S,8R)-erythro-guaiacylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (1), (7R,8S)-erythro-guaiacylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (2), (7S,8R)-erythro- syringylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (3) and (7R,8S)-erythro- syringylglycerol-beta-O-4'-sinapyl ether 9-O-beta-D-glucopyranoside (4), were isolated from the leaves of Osmanthus ilicifolius. Their structures were established on the basis of NMR, circular dichroism (CD), MS and chemical data. The NMR assignments for the compounds were carried out using (1)H, (13)C, COSY, HMQC, HMBC and NOESY NMR experiments.     

Synthesis of carbazoles from N-(N,N-diarylamino)phthalimides with aluminum chloride via diarylnitrenium ions.

Generation of diarylnitrenium ions from N-(N,N-diarylamino)phthalimides by treatment with AlCl(3) in benzene or in 1,2-dichloroethane leads to formation of carbazoles by intramolecular C-C bond formation. The reaction proceeds in synthetically useful yields.     

Solubilization of Polar Oils in Surfactant Self-Organized Structures

The cloud temperature of 2 wt% C(12)EO(8) aqueous solutions decreases upon addition of sarcosinate-lauroyl isopropyl (SLIP), 1-dodecanol, and m-xylene, whereas it increases in glycerol tris(2-ethylhexanoic) ester (TEH), isopropyl myristate (IPM), and saturated hydrocarbon systems. A three-phase microemulsion is formed at equal weights of water and oil in the IPM system, but a lamellar liquid crystal (L(alpha)) is present in the SLIP system at the balanced temperature. The effect of added oil on the phase transition of the hexagonal (H(1)) phase was also investigated by means of SAXS study. The H(1)-L(alpha) transition occurs upon addition of SLIP or 1-dodecanol whereas the H(1)-I(1) (discontinuous micellar cubic) phase transition takes place in TEH or IPM systems. These differences in phase behavior are attributed to the placement of solubilized oil in micelles: In the former systems, oil tends to penetrate in the surfactant palisade layer and induces the surfactant layer curvature in micelles to be less positive, while the penetration tendency is small and the opposite effect on the curvature is induced upon addition of the latter oils. Copyright 2001 Academic Press.     

Development of a supercritical fluid extractor coupled with a time-of-flight mass spectrometer for online detection of extracts.

A combined apparatus of a supercritical CO2 extractor (SFE) and a time-of-flight mass spectrometer (TOF-MS) was developed aiming at the direct analysis of extracts. A fused-silica capillary acts as both a pressure restrictor and an effluent injection nozzle into the TOF-MS. The tip of the nozzle was narrowed by melting and abrasion so that a greater pressure drop occurred at the tip. In the TOF-MS chamber, differential pumping between the main and ionization chamber kept the pressure in the ionization chamber at around 10(-3) Pa when the SFE pressure was at 9.7 to 29.4 MPa. The TOF-MS performance, a mass resolution of 263 at m/z = 146, and a sensitivity of 1.6 ng (p-dichlorobenzene) were certified by direct injection of a standard organic solution. Online detection of SFE effluent containing naphthalene, p-dichlorobenzene, phenanthrene and pyrene were successfully performed by the TOF-MS only for 48000 ionization cycles corresponding to 7.5 s.