排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Ultraviolet and visible spectroscopy studies of the fullerene C60 melted in n-hexane or adsorbed on dielectric solids. Experiments of spectroscopy have been carried out, between the far ultraviolet and the near infrared, with pure C60 or containing endohedral complexes rare gas atom-C60, melted in n-hexane, and also pure C60 adsorbed on surfaces of solids.Several phenomena have been observed: 1. a charge transfer due to the influence of interactions between the molecules of C60 and surfaces of solids, yielding new transitions observed in the far ultraviolet ; and interpreted as super excited states of Rydberg type; 1.1. red and blue shifts for some transitions of adsorbed C60, interpreted on the basis of attractive, or turned repulsive, dispersion forces; 1.1.1. emission processes for several transitions of adsorbed C60, explained on the basis of a resonant coupling between these transitions and modes of the surface plasmon induced by the collective excitations of the C60 molecule; this kind of process might be drawn to the Faraday instability in acoustics. 相似文献
6.
We report on the first study of the photocatalytic performance of immobilized smallest titanium oxide oxoparticles of the size 2R = 5.0 nm on a glass support. The nanometric particles are prepared in the sol-gel reactor with rapid reagent mixing and temperature, atmosphere, and particle size control. The surface coverage is achieved by inserting the support into the reactor solution during the induction period, where chemically active nanoparticles are relatively stable. We show that this immobilized amorphous oxo phase of titanium oxide exhibits considerable activity toward photocatalytic degradation of trichloroethylene in the gas phase. Moreover, one of the important factors appears to be the catalyst surface preparation, which has to be free of the adsorbed alcohol molecules. UV-assisted exchange between propoxy and hydroxy groups is suggested as the surface activation mechanism. The film thickness is expected to strongly affect the material photocatalytic efficiency because of the internal traps population. 相似文献
7.
8.
9.
[reaction: see text] Bicyclic and tricyclic gamma-butyrolactones with 5,7-, 5,6,5-, 5,6,6-, or 5,7,5-fused ring systems, being found in xanthanolides, eudesmanolides, and guaianolides, were readily synthesized from methyl furan-2-carboxylic acid. Key steps were a copper(I)-catalyzed asymmetric cyclopropanation, Sakurai allylations, intramolecular ene reactions, and ring-closing metathesis reactions. 相似文献
10.
Chhor RB Nosse B Sörgel S Böhm C Seitz M Reiser O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(1):260-270
The development of a new method for the enantioselective synthesis of disubstituted gamma-butyrolactones is reported. Based on this strategy, the total synthesis of three paraconic acids, that is (-)-roccellaric acid, (-)-nephrosteranic acid and (-)-protopraesorediosic acid, and the formal total synthesis of (-)-methylenolactocin and (-)-protolichesterinic acid is described, which are important because of their antibiotic and antitumor properties. Key steps of the synthesis are copper(I)-catalyzed asymmetric cyclopropanations of furans, highly diastereoselective Sakurai allylations, Lewis acid or Lewis base catalyzed retroaldol/lactonization cascades, and ruthenium(II)-catalyzed, intermolecular cross metathesis reactions. 相似文献