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91.
This review article summarizes our recent researches for molecular design of polyoxometalates (POMs) and their related compounds
for environmentally-friendly functional group transformations. The divacant POM [γ-SiW10O34(H2O)2]4− exhibits high catalytic performance for mono-oxygenation-type reactions including epoxidation of olefins and allylic alcohols,
sulfoxidation, and hydroxylation of organosilanes with H2O2. We have successfully synthesized several POM-based molecular catalysts (metal-substituted POMs) with controlled active sites
by the introduction of metal species into the divacant POM as a “structural motif”. These molecular catalysts can efficiently
activate H2O2 (vanadium-substituted POM for epoxidation) and alkynes (copper-substituted POM for click reaction and oxidative homocoupling
of alkynes). The aluminum-substituted POM exhibits Lewis acidic catalysis for diastereoselective cyclization of (+)-citronellal
to (−)-isopulegol. In addition, we have developed POM-based “molecular heterogeneous catalysts” by the “solidification” and
“immobilization” of catalytically active POMs. 相似文献
92.
Minakata K Nozawa H Gonmori K Yamagishi I Suzuki M Hasegawa K Watanabe K Suzuki O 《Analytical and bioanalytical chemistry》2011,400(7):1945-1951
An electrospray ionization tandem mass spectrometric (ESI-MS-MS) method has been developed for the determination of cyanide
(CN–) in blood. Five microliters of blood was hemolyzed with 50 μL of water, then 5 μL of 1 M tetramethylammonium hydroxide solution
was added to raise the pH of the hemolysate and to liberate CN– from methemoglobin. CN– was then reacted with NaAuCl4 to produce dicyanogold, Au(CN)2–, that was extracted with 75 μL of methyl isobutyl ketone. Ten microliters of the extract was injected directly into an ESI-MS-MS
instrument and quantification of CN– was performed by selected reaction monitoring of the product ion CN– at m/z 26, derived from the precursor ion Au(CN)2– at m/z 249. CN– could be measured in the quantification range of 2.60 to 260 μg/L with the limit of detection at 0.56 μg/L in blood. This
method was applied to the analysis of clinical samples and the concentrations of CN– in the blood were as follows: 7.13 ± 2.41 μg/L for six healthy non-smokers, 3.08 ± 1.12 μg/L for six CO gas victims, 730 ± 867 μg
for 21 house fire victims, and 3,030 ± 97 μg/L for a victim who ingested NaCN. The increase of CN– in the blood of a victim who ingested NaN3 was confirmed using MS-MS for the first time, and the concentrations of CN– in the blood, gastric content and urine were 78.5 ± 5.5, 11.8 ± 0.5, and 11.4 ± 0.8 μg/L, respectively. 相似文献
93.
Two polyoxometalate assemblies, TBA(9)[{γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)] (1; TBA = tetra-n-butylammonium) and TBA(6)Li(3)[{γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)]·18H(2)O (2), were synthesized by trimerization of a dialuminum-substituted silicotungstate monomer. Both 1 and 2 possessed a layered structure composed of a basal sheet unit [TBA(3){γ-H(2)SiW(10)O(36)Al(2)(μ-OH)(2)(μ-OH)}(3)](6-) and interlayer cations. The interconversion between 1 and 2 reversibly took place through interlayer cation exchange. 相似文献
94.
Imoto M Matsui Y Takeda M Tamaki A Taniguchi H Mizuno K Ikeda H 《The Journal of organic chemistry》2011,76(15):6356-6361
Observations show that nitroanilines exhibit an unusually high S(N)Ar reactivity with OH(-) in aqueous media in reactions that produce nitrophenols. S(N)Ar reaction of 4-nitroaniline (2a) in aqueous NaOH for 16 h yields 4-nitrophenol (4a) quantitatively, whereas a similar reaction of 4-nitrochlorobenzene (1a) gave 4a in 2% yield together with recovered 1a in 97%, suggesting that the leaving ability of the NH(2) group far surpasses that of Cl under these conditions. An essential feature of S(N)Ar reactions of nitroanilines is probably that the NH(2) leaving group participates in a hydrogen-bonding interaction with H(2)O. Density functional theory (DFT) calculations for a set of 4-nitroaniline, OH(-), and H(2)O suggest a possible formation of a Meisenheimer complex stabilized by hydrogen-bonding interactions and a six-membered ring structure. The results obtained here contrast with conventional S(N)Ar reactivity profiles in which nitroanilines are nearly unreactive with nucleophiles in organic solvents. 相似文献
95.
Journal of Algebraic Combinatorics - We characterize Y/T-system-type difference equations arising from cluster algebras by triples of matrices, which we call T-data, that have a certain symplectic... 相似文献
96.
The c(4 × 2) structures in (0 0 1) surfaces of Si and Ge have been studied by low-energy electron diffraction (LEED). Using a proper cleaning method for the Si surface, we were able to observe clear c(4 × 2) LEED patterns up to incident energy of ∼400 eV as well as the Ge surface. Extensive experimental intensity-voltage curves allowed us to optimize the asymmetric dimer model up to the eighth layer (including the dimer layer) in depth in the dynamical LEED calculation. Optimized structural parameters are almost the same for the Si and Ge except for the height of the buckled-up atom of the asymmetric dimer. For the Ge surface, the structural parameters are in excellent agreement with those obtained by a previous theoretical calculation. The tilt angle and bond length of the dimer are 18 ± 1 (19 ± 1)° and 2.4 ± 0.1 (2.5 ± 0.1) Å for the Si(0 0 1) (Ge(0 0 1)), respectively. 相似文献
97.
The interaction between metal ions and bovine serum albumin (BSA) was studied by using a piezoelectric quartz crystal (PQC) arranged in the electrode-separated configuration. A silanized surface of the PQC was coated with a BSA membrane via a coupling reaction with glutaraldehyde. The frequency shifts obtained from PQC coated with a BSA membrane suggested that various kinds of metal ions could be adsorbed onto the BSA membrane from aqueous solutions containing a low concentration of metal ions (2 or 10 micromol dm(-3)), only when the BSA was denatured with an alkaline solution. Anionic species of Pt(IV) and Au(III) were adsorbed onto the denatured BSA membrane from an acetic acid solution at pH 2.2, and cationic species of Cd(II), Zn(II), Co(II), Ni(II), Cu(II), and Ag(I), and cations, such as Ca2+, Ba2+, and Mg2+, were adsorbed from ammonia buffer at pH 9.5, whereas Al(III), Cr(III), Fe(III), Hg(II), and Pb(II) were hardly adsorbed. The adsorption mechanisms of these metal ions are discussed, based on the electrostatic interaction between the metal ions and the denatured BSA membrane, and complex formation between the metal ions and amino acid residues of the denatured BSA. Further, the PQC coated with a denatured BSA membrane was applied to the determination of Pt and Cd, using large frequency shifts for Pt(IV) and Cd(II). 相似文献
98.
M. Matsui M. Suzuki K. Mizuno K. Funabiki S. Okada T. Kobayashi M. Kadowaki 《Liquid crystals》2004,31(11):1463-1467
Novel dichroic fluorescent 2- and 2,7-disubstituted perfluorophenazines exhibit emission maxima in the range 570-600 nm in MLC-2039. The order parameter of fluorescence was observed in the range 0.29-0.49. 相似文献
99.
J. Chen H. Mizuno H. Kawano A. Miyawaki K. Midorikawa 《Applied physics. B, Lasers and optics》2006,85(1):45-48
We experimentally demonstrated two-photon pumping of random lasers using picosecond and nanosecond pump lasers. The picosecond laser pumping experiment was performed with 400 ps laser pulses at 770 nm, and the gain media was a Coumarin 480D dye solution doped with TiO2 nanoparticles. Onset of laser action was observed at a pump laser pulse energy below 500 μJ. The nanosecond laser pumping experiment was performed with 7 ns laser pulses at 1064 nm, and the gain media was a Rhodamine 640 dye solution doped with TiO2 nanoparticles. Onset of laser action was observed at a pump laser energy ∼18 mJ. Our results suggest that there exists an optimal pulse duration of the pumping laser in two-photon pumped random lasing that leads to minimum photodamage of the gain media and still keeps a high pumping efficiency. PACS 33.50.Dq; 42.55.Mv; 42.55.Zz 相似文献
100.
Photo- and thermal-diffusion effects of Ag and Cu into As2S3 bulk glass have been studied. It has been clarified that the photo-diffusion process is attributed to a purely optical effect. Some differences in diffusing process between Ag and Cu have been clearly shown both for the photo- and thermal-diffusions. 相似文献