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851.
[reaction: see text] We have investigated the olefin metathesis from alkenyl Baylis-Hillman adducts using second-generation Grubbs catalyst. In the experiment, the ring-closing metathesis (RCM) product could not be found, while the cross-metathesis (CM) products were found. The computational studies provided consistent explanations for the experimental result. The most limiting factor for the RCM process using second-generation Grubbs catalyst is caused by the high strain and steric effect in the metallacyclobutane intermediates. 相似文献
852.
催化动力学分光光度法测定痕量锰(Ⅱ) 总被引:3,自引:0,他引:3
严进 《广东微量元素科学》2003,10(9):60-62
研究了氢氧化钠介质中 ,痕量锰催化过氧化氢氧化桑色素褪色反应及其动力学条件 ,建立了催化动力学测定痕量锰的新方法。Mn (Ⅱ )的测定线性范围为 0 0 0 5~ 0 0 60 μg/2 5mL ,检出限为 7 8× 1 0 - 10 g·mL- 1。用于大米中痕量Mn (Ⅱ )的测定 ,结果满意。 相似文献
853.
Inorganic nitrogen species (nitrate, nitrite and ammonium ions) were simultaneously determined by microcolumn ion chromatography. Nitrate and nitrite were determined by UV detection at 206 nm, whereas ammonium ion was determined by fluorescence detection at excitation 410 nm and emission 470 nm. The latter fluorescence detection is based on the postcolumn reaction of ammonium ion with o-phthalaldehyde in the presence of 2-mercaptoethanol. Effects of the reagent concentration, pH, and other reaction conditions on the signal intensity were examined, and the optimum condition was explored. The present method allowed simultaneous determination of nitrate, nitrite and ammonium ions in river water. 相似文献
854.
Fe-Co-Ni合金纳米线有序阵列的模板合成与磁性 总被引:10,自引:0,他引:10
以二次阳极氧化的氧化铝膜为模板,用电化学沉积的方法成功地合成了Fe-Co-Ni三组份有序纳米线阵列.扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察表明纳米线表面光滑、有序、高长径比;磁性测量表明,其矫顽力较同组份的膜材料有较大的提高.将样品在惰性气体氛围中不同温度下退火,随着退火温度增加,其纵向矫顽力有一个极值,而对应的横向矫顽力没有类似的变化,关于这一现象的机理,本文进行了初步的讨论. 图5参15 相似文献
855.
Li H Li Y Zhai J Cui G Liu H Xiao S Liu Y Lu F Jiang L Zhu D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(24):6031-6038
A novel, water-soluble, cationic PPV derivative poly[(2,5-bis(3-bromotrimethylammoniopropoxy)-phenylene-1,4-divinylene)-alt-1,4-(2,5-bis(2-(2-hydroxyethoxy)ethoxy))phenylene vinylene] (BH-PPV) has been synthesized by a Heck coupling reaction. Multilayered assemblies of the BH-PPV and the sodium salt of hexa(sulfobutyl)fullerenes (C(60)-HS) were fabricated successfully by an alternate deposition technique. The multilayer structures were studied by UV/Vis spectroscopy, small angle X-ray diffraction, and atomic force microscopy. The photoinduced charge transfer property of the self-assembled multilayer film was also measured by a three-electrode cell technique. A steady and rapid cathodic 5.5 microA cm(-2) photocurrent response was measured as the irradiation of the multilayer film was switched on and off. Importantly, the response of on/off cycling is prompt and reproducible. A possible mechanism for the electron-transfer process is proposed. 相似文献
856.
Roland Wilberger Holger Piotrowski Marcus Warchhold Ingo‐Peter Lorenz 《无机化学与普通化学杂志》2003,629(14):2485-2492
Novel Neutral and Cationic Mono‐Aziridine Complexes of the Type [CpMn(CO)2Az], [CpCr(NO)2Az]+, and [(Ph3P)(CO)4ReAz]+ via CO‐, Hydride‐, and Chloride‐Elimination Reactions The monoaziridine complexes 1 — 5 are obtained by three differently induced substitution reactions. The photolytically induced CO substitution reaction of [CpMn(CO)3] with 2, 2‐dimethylaziridine leads to the neutral N‐coordinate aziridine complex [Cp(CO)2Mn{$\overline{N(H)CMe2C}$ H2}] ( 1 ). The protonation of [(Ph3P)(CO)4ReH] with CF3SO3H and consecutive treatment with 2, 2‐dimethylaziridine or 2‐ethylaziridine gives the salt‐like aziridine complexes [(Ph3P)(CO)4Re{$\overline{N(H)CMe2C}$ H2}](CF3SO3) ( 2 ) or [(Ph3P)(CO)4Re{ H2}](CF3SO3) ( 3 ) by hydride elimination reactions. The like‐wise salt‐like complexes [Cp(NO)2Cr{$\overline{N(H)CMe2C}$ H2}](BF4) ( 4 ) and [Cp(NO)2Cr{ H2}](CF3SO3) ( 5 ) are synthesized from [CpCr(NO)2Cl] by chloride elimination with AgX (X = BF4, CF3SO3) in the presence of 2, 2‐dimethylaziridine or 2‐ethylaziridine, respectively. As a result of X‐ray structure analyses, the metal atoms are trigonal pyramidally ( 1, 4, 5 ) or octahedrally ( 2, 3 , cis‐position) configurated; the intact three‐membered rings coordinate through the distorted tetrahedrally configurated N atoms. All compounds 1‐5 are stable with respect to the directed thermal alkene elimination to give the corresponding nitrene complexes; the IR, 1H‐ and 13C{1H}‐NMR, and MS spectra are reported and discussed. 相似文献
857.
Wen J Chowdhury P Wills NJ Wannemuehler Y Park J Kesavan S Carpenter S Kraus GA Petrich JW 《Photochemistry and photobiology》2002,76(2):153-157
The synthesis of a molecule containing hypericin and luciferin moieties joined by a tether is reported. The light-induced (in vitro) antiviral activity as well as the photophysical properties of this new compound are measured and compared with those of the parent compounds, hypericin and pseudohypericin. This tethered molecule exhibits excited-state behavior that is very similar to that of its parent compounds and antiviral activity that is identical, within experimental error, to that of its more closely related parent compound, pseudohypericin. The implications for a photodynamic therapy that is independent of external light sources are discussed. 相似文献
858.
Polyacrylamide (PAL) was physically adsorbed onto a hydroxylated silicon surface to form a uniform PAL film and the up-top PAL thin film was treated by nitrogen (N2) plasma for surface modification. The atomic composition of the modified surface of the PAL film adsorbed on silicon substrate was analyzed with Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The surface energy of PAL film was calculated from the data of contact angle of three-probe liquid. The FTIR results show an increase of peak intensity at 1214 cm−1 (NH2 stretch vibration) after the nitrogen plasma treatment, which confirms that the nitrogen was grafted to the PAL surface in the process of N2-plasma treatment. The XPS results show that the ratio of relative intensity of N1s to O1s increases with increasing the plasma treatment time, which further affirms the formation of the amine groups on the PAL surface after the nitrogen plasma treatment. The surface tension increases with increasing the plasma grafting time. However, the surface energy decreases rapidly at the early stage when stored in air and approaches to an equilibrium value. It suggests that some physically-adsorbed ions and alkyl radicals on PAL surface can rapidly lose their activities. The increase of the surface tension of the plasma treated PLA films is due to the amine groups covalently grafted to PAL surface. 相似文献
859.
860.
Ning GL Li XC Munakata M Gong WT Maekawa M Kamikawa T 《The Journal of organic chemistry》2004,69(4):1432-1434
Phenyl-substituted cyclopentadienes are proved to form phenylated pyrylium cations in the presence of silver(I) perchlorate by insertion of an oxygen atom into the cyclopentadiene-ring. Three phenylated pyrylium compounds, [(Ph(5)C(5)O(+))(ClO(4)(-))](2)(CH(2)Cl(2)) (1), Ag(ClO(4))(H(2)O)(Ph(4)HC(5)O(+)) (ClO(4)(-)) (2), and (Ph(3)H(2)C(5)O(+))(ClO(4)(-)) (3) have been synthesized and characterized. A possible reaction pathway and formation mechanism of the pyrylium cation are proposed and discussed. 相似文献