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101.
102.
Raman scattering spectra on a layer type compound 3RNbS2 were measured at 300 and 77 K, and three peaks were observed at 382, 325 and 281 cm?1 at 300 K. The vibration modes were analyzed in terms of Bromley's nearest neighbour model, and a good agreement with the experiment was obtained. 相似文献
103.
104.
In GeS glasses ESR signals were observed at g ? 2.00. The signal in GeS2 was a single Gaussian line with linewidth of ca. 15 G. The signal in the glass containing more sulfer than GeS2 changed into multi-lined spectra. The signal disappeared by addition of 5 molar % arsenic. Discussion is given in the concept of ‘defects’ in the chalcogenide glass. 相似文献
105.
106.
A Reformatsky-type aldol reaction of alpha-chloroketones with aldehydes has been achieved using reactive barium as a low-valent metal in THF; this one-pot process is more effective for obtaining the desired beta-hydroxy ketones in high yields than the stepwise process in which barium enolates are prepared prior to the reaction with aldehydes. 相似文献
107.
Busacca CA Grossbach D Campbell SJ Dong Y Eriksson MC Harris RE Jones PJ Kim JY Lorenz JC McKellop KB O'Brien EM Qiu F Simpson RD Smith L So RC Spinelli EM Vitous J Zavattaro C 《The Journal of organic chemistry》2004,69(16):5187-5195
The Boehringer-Ingelheim phosphinoimidazoline (BIPI) ligands were applied to the formation of chiral quaternary centers in the asymmetric Heck reaction. Several different substrates were examined in detail, using more than 70 members of this new ligand class. Hammett relationships were determined through systematic variation of the ligand electronics. All substrates showed essentially the same Hammett behavior, where enantioselectivity increased as the ligands were made more electron-deficient. Ligand optimization has led to catalysts which give the highest enantioselectivities reported to date for these difficult systems. 相似文献
108.
Yusuke Arai Tetsuji Yano Shuichi Shibata 《Journal of Sol-Gel Science and Technology》2004,32(1-3):189-194
Microspheres of refractive index of nD > 2.0 have been investigated. The organic-inorganic hybrid microspheres of nD = 1.72 were prepared by the vibrating orifice technique using titanium-tetra-n-butoxide (TTBu) and diphenyldimethoxysilane (DPhDMS). For lasing demonstration, Eu3+-doped microspheres were prepared using europium (III) thenoyltrifluoroacetonate [Eu(TTFA)3] as the dopant. The particles have good spherical shape, smooth surface and high optical transparency. The diameters of the particles could be controlled to within 0.1 m. Subsequent heating of the microspheres at 550°C under oxygen atmosphere resulted in an increase in the refractive index up to nD = 2.6 with retention of the spherical shape. Resonant emission was confirmed from Eu3 +-doped microspheres after heating at 400–550°C, by pumping with the 514.5 nm line of a CW- Ar+laser. 相似文献
109.
Sekiguchi A Inoue S Ichinohe M Arai Y 《Journal of the American Chemical Society》2004,126(31):9626-9629
The highly twisted tetrakis(di-tert-butylmethylsilyl)disilene 4 was prepared and reacted with (t)BuLi in THF, producing disilene anion radical 5 upon one-electron reduction. The anion radical 5 was isolated in the form of its lithium salt as extremely air- and moisture-sensitive red crystals. The molecular structure of 5 was established by X-ray crystallography, which showed a nearly orthogonal structure (twisting angle of 88 degrees ) along the central Si-Si bond, with a length of 2.341(5) A, which is 3.6% elongated relative to that of 4. The interesting feature of 5 is that one of the central Si atoms has radical character, whereas the other Si atom has silyl anion character. An electron spin resonance (ESR) study of the hyperfine coupling constants of the (29)Si nuclei indicates that rapid spin exchange occurs between these central Si atoms on the ESR time scale. 相似文献
110.
Mahon KP Ortiz-Meoz RF Prestwich EG Kelley SO 《Chemical communications (Cambridge, England)》2003,(15):1956-1957
A novel class of DNA cleavage agents are reported that derive activity from amino acids tethered to a photoactive intercalator. 相似文献