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761.
Hydrogen absorption and emission characteristics of Pt-Li2ZrO3 bi-layer materials exposed to normal air at room temperature have been studied by means of elastic recoil detection analysis(ERD), Rutherford backscattering spectroscopy (RBS), weight gain measurement (WGM) and thermal desorption spectroscopy (TDS). The Pt/Li2ZrO3/Pt sandwich specimens have been found to absorb H at the Pt surface from H2O vapor, store it in Li2ZrO3, and emit 80% of it as H2 gas, when they are heated at 100 °C for 10 min. Data obtained by WGM shows that the weight gain increases linearly with increasing the exposure time. TDS analysis also shows that the main species of gases re-emitted are H2 and H2O. Moreover, the hydrogen storage rate in Li2ZrO3 is shown to be controlled by the hydrogen absorption rate at the Pt surface, based on the hydrogen absorption and storage model proposed. The maximum storage capacity of Li2ZrO3 has been estimated to be 0.15 Nl/cm3 from the saturation hydrogen concentration, (1/2)H/Li2ZrO3, measured by means of the ERD technique. 相似文献
762.
Franciele Wolfart Amanda Maciel Noemi Nagata Marcio Vidotti 《Journal of Solid State Electrochemistry》2013,17(5):1333-1338
This paper concerns the deposition of metal alloys formed by nickel and copper on electrode surface aiming at the development of electrocatalytic systems. Such alloys were formed on platinum electrodes by direct reduction of Ni2+ and Cu2+ sulfate salts in different proportions in a simple and straightforward electrochemical treatment. After the deposition, the conversion to the electrocatalytic oxide form was done in alkaline solutions by cyclic voltammograms. The experimental parameters, such as deposition time and the proportion of copper and nickel in the synthetic solution, were investigated toward the catalytic oxidation of glucose. The materials were characterized by electrochemical experiments, infrared and Raman spectroscopies, and X-ray diffraction, showing that the material is not a simple mixture of nickel and copper oxides. The modified electrodes showed remarkable electrocatalytic properties, indicating an interesting application in the sensor and fuel cell development. 相似文献
763.
Yasuyuki Nakamura Kouji Nakanishi Shigeru Yamago Yoshinobu Tsujii Kenichi Takahashi Takashi Morinaga Takaya Sato 《Macromolecular rapid communications》2014,35(6):642-648
The direct synthesis of structurally well‐defined protic polymeric ionic liquid (PIL) with controlled molecular weight and molecular weight distribution is examined using N,N‐diethyl‐N‐(2‐methacryloylethyl) ammonium bis(tri‐fluoromethylsulfonyl)imide (DEMH‐TFSI) as a monomer. Three polymerization methods, namely, atom transfer radical polymerization (ATRP), activators regenerated by electron transfer (ARGET)‐ATRP, and organotellurium‐mediated living radical polymerization (TERP) are employed in this study. While the polymerization by ATRP is slow and does not reach high monomer conversion that under ARGET‐ATRP and TERP proceeds smoothly and affords structurally well‐defined poly(DEMH‐TFSI)s. TERP is especially efficient for the control and poly(DEMH‐TFSI)s with low to high molecular weights ( = 49 100–392 500) and narrow molecular weight distributions (/ = 1.17–1.46) are obtained. These results represent the first example of synthesis of a structurally well‐defined protic, ammonium PIL by direct polymerization of the protic ionic liquid monomer. The polymerization of N,N‐diethyl‐N‐(2‐methacryloylethyl)‐N‐methylammonium bis(trifluoromethylsulfonyl)imide (DEMM‐TFSI), which possesses a quaternary ammonium salt, also proceeds in a highly controlled manner under TERP conditions. A diblock copolymer, polystyrene‐block‐poly(DEMH‐TFSI), is also successfully synthesized by TERP.
764.
Toshi Nagata 《Research on Chemical Intermediates》2014,40(9):3183-3198
Quinones are essential components in many biological systems, notably in photosynthesis. This is largely due to the characteristic proton-coupled redox chemistry of quinones. This review article overviews the use of quinones in studies on artificial photosynthesis, as one-electron electron acceptors, reversible proton/electron carriers, and replacements for sacrificial oxidant and reductants in photosynthetic chemical conversion. Topics included are the early attempts on intramolecular photoinduced electron transfer involving quinones, subsequent reactions after photoinduced electron transfer between pigments and quinones, photochemistry in molecular assemblies containing quinones, and photochemical quinone/hydroquinone interconversion. 相似文献
765.
Cover Picture: Switching of Single‐Molecule Magnetic Properties of TbIII–Porphyrin Double‐Decker Complexes and Observation of Their Supramolecular Structures on a Carbon Surface (Chem. Eur. J. 36/2014) 下载免费PDF全文
766.
Tanaka SY Tagashira N Chiba K Yasuda M Baba A 《The Journal of organic chemistry》2008,73(16):6312-6320
A highly practical reductive cross-aldol reaction of alpha-bromoaldehydes with various aldehydes has been developed using Ge(II)Cl 2 to produce aldehyde germanium(IV) aldolates, which were directly transformed to various multifunctionalized compounds. A remarkable change in stereoselectivity depended on the alpha-bromoaldehydes employed; secondary alpha-bromoaldehydes gave syn selectivities, while tertiary alpha-bromoaldehydes accomplished the synthesis of anti-selective aldol products with a quaternary carbon center. NMR studies and X-ray analysis strongly suggested the formation of germanium enolate in the reaction of alpha-bromoaldehyde 2h with GeCl 2-dioxane. Detailed mechanistic studies, including NMR analysis and ab initio calculations, revealed the generation of stable germanium aldolates, which was due to the remarkably low Lewis acidity of the germanium(IV). 相似文献
767.
768.
Kakuchi R Nagata S Sakai R Otsuka I Nakade H Satoh T Kakuchi T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(33):10259-10266
A colorimetric detection susceptible to the dimensions of guest counteranions has been demonstrated by using poly(phenylacetylene) with L-leucine and urea functionalities (poly-PA-Leu). Poly-PA-Leu was prepared from N-(4-ethynylphenylcarbamoyl)-L-leucine ethyl ester (PA-Leu) by using [Rh(+){eta(6)-C(6)H(5))B(-)(C(6)H(5))(3)}(2,5-norbornadiene)] as a catalyst. The biased helical conformation of poly-PA-Leu was demonstrated through Cotton effects in the circular dichroism (CD) spectra. The addition of ammonium salts, including tetra-n-butylammonium acetate, tetra-n-butylammonium chloride, and tetra-n-butylammonium bromide anions (CH(3)COO(-), Cl(-), and Br(-)), into the poly-PA-Leu solution intensified the CD responses of poly-PA-Leu, which is indicative of the chiral adjustability of anion recognition by using urea groups. In addition, the combination of poly-PA-Leu with the CH(3)COO(-), Cl(-), and Br(-) anions promoted large redshifts in the absorption spectra, thus providing dramatic color changes from pale yellow to red. Guest dependency in the CD and UV/Vis spectra was clearly correlated with the size of the counteranions. Fundamentally, the addition of tetra-n-butylammonium nitrate, tetra-n-butylammonium hydrogen sulfate, tetra-n-butylammonium perchlorate, tetra-n-butylammonium azide, tetra-n-butylammonium fluoride, and tetra-n-butylammonium iodide anions (NO(3) (-), HSO(4) (-), ClO(4) (-), N(3) (-), F(-), and I(-)) has no effect on either the CD or UV/Vis profiles of poly-PA-Leu. The guest specificity observed in the CD and UV/Vis spectra clearly demonstrated the guest-dimension selectivity of poly-PA-Leu in counteranion recognition. 相似文献
769.
M Nakamura H Tahara K Takahashi T Nagata H Uoyama D Kuzuhara S Mori T Okujima H Yamada H Uno 《Organic & biomolecular chemistry》2012,10(34):6840-6849
Benzene-fused bis-(borondipyrromethene)s (bis-BODIPYs) were synthesized by retro-Diels-Alder reaction of the corresponding bicyclo[2.2.2]octadiene-fused (BCOD-fused) bis-BODIPYs, which were, in turn, prepared from 4,8-ethano-4,8-dihydropyrrolo[3,4-f]isoindole derivatives. The π-fused bis-BODIPY chromophores were designed to show intensive absorption and strong fluorescence in the near-infrared region and not to have any strong absorption in the visible region. A 6,10-dibora-5a,6a,9a,10a-tetraaza-s-indaceno[2,3-b:6,5-b']difluorene derivative (syn-bis-benzoBODIPY) obtained by a thermal retro-Diels-Alder reaction of the corresponding BCOD-fused BODIPY dimer has strong absorption and emission bands at 775 and 781 nm, respectively. The absolute quantum yield is 0.36. The absorption is more than 5.0 times stronger than other absorptions observed in the visible region. In the case of 6,15-dibora-5a,6a,14a,15a-tetraaza-s-indaceno[2,3-b:6,7-b']difluorene derivatives (anti-bis-benzoBODIPY), the absorption and emission maxima exceed 840 nm. 相似文献
770.
Tetrahydroquinolines (THQs), a new class of nonsteroidal selective androgen receptor (AR) modulators, have two indispensable functional groups, that is, a hydroxyl group for AR binding and a nitro group for agonistic activity. Interestingly, switching the nitro to a cyano group, the compound acts as an antagonist. To understand this phenomenon, molecular dynamics simulations were applied for dihydrotestosterone (DHT) and representative THQs complexes with AR. Upon ligand binding, the hydroxyl group formed a tight hydrogen-bond (H-bond) with Asn705 on Helix 3 (H3). The immobilization of Asn705 on H3 is helpful in the formation of tight H-bonds with Asp890 on loop 11-12, and this immobilization consequently leads to a stabilization of H12. The difference in the DHT carbonyl isosteres affected the presence or absence of the H-bonds between the hydroxyl group of THQ and Thr877 and the distortion of H12, which is caused by the methyl group of THQ. Thus, the binding, agonist, and antagonist functions were controlled by subtle structural changes in THQ. 相似文献