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排序方式: 共有472条查询结果,搜索用时 15 毫秒
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R. Centore P. Riccio S. Fusco A. Carella A. Quatela S. Schutzmann F. Stella F. De Matteis 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2719-2725
We have prepared new polyesters containing quadratic, nonlinear optical (NLO) active chromophores covalently incorporated into the main chain. In these polymers, the sequence of the chromophore units along the main chain is rigorously head to tail. All the polyesters are processable, both in the melt and in solution. For one polyester, a full second‐order NLO characterization has been performed. An out‐of‐resonance d33 coefficient of 21 pm/V at 1368 nm has been measured. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2719–2725, 2007 相似文献
3.
Lucien Stella 《Angewandte Chemie (International ed. in English)》1983,22(5):337-350
Many N-chloroalkylamines with double bond(s) dissociate homolytically to give chlorine atoms and aminyl radicals which undergo intramolecular cyclization reactions. Here, the nature of the aminyl radicals (neutral, protonated, or complexed to metal salts) appears to be important. The reactivity varies strongly from one species to another, and their selectivities can be different towards addition, substitution, abstraction, or dimerization reactions. A good synthetic tool appears to be the “complexed radical”, which is generated under mild conditions. A variety of β-functionalized, substituted, fused, or bridged azaheterocycles with alkaloid part structures thus become easily accessible in high yields, in a regio- and, possibly, stereoselective manner. Many examples are discussed illustrating the synthetic possibilities, limitations, and mechanistic features of this cyclization process. 相似文献
4.
Dendritic molecular capsules for hydrophobic compounds 总被引:1,自引:0,他引:1
Morgan MT Carnahan MA Immoos CE Ribeiro AA Finkelstein S Lee SJ Grinstaff MW 《Journal of the American Chemical Society》2003,125(50):15485-15489
Reichardt's dye, a highly solvatochromic dye, was encapsulated within poly (glycerol succinic acid) ([Gn]-PGLSA-OH) dendrimers to investigate the interior environment of these dendritic macromolecules. The absorption maximum for the encapsulated Reichardt's dye in water was indicative of a relatively high dielectric constant present within the dye/dendrimer complex. (1)H NMR of the encapsulated complex showed the presence of aromatic protons from Reichardt's dye along with the aliphatic protons of the dendrimer. Additionally, there were substantial changes in T(1) and T(2) times of the encapsulated dye when compared with the free dye, and (1)H NOESY spectra for the complex showed a significant number of intermolecular NOE cross-peaks. These data reveal the close through-space proximity of the dye to the dendrimer and the restricted motion of the encapsulated dye. To demonstrate the potential use of these macromolecules as drug delivery vehicles, the poorly water-soluble anticancer drug 10-hydroxycamptothecin (10HCPT) was encapsulated within a carboxylated PGLSA dendrimer ([G4]-PGLSA-COONa). Cytotoxicity assays with human breast cancer cells showed a significant reduction of cell viability, demonstrating that 10HCPT retains activity upon encapsulation. 相似文献
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Heinz Günter Viehe Robert Mernyi Lucien Stella Zdenek Janousek 《Angewandte Chemie (International ed. in English)》1979,18(12):917-932
The 100 yers old Wurster's salts have long been recognized as compounds with redical cations. Their unusual stabilization derives partly form capto-dative (cd) substitution. This principle is now discussed as one factor of radical stabilization and it is applied to simple methine derivatives. cd-Substitution has synthetically useful applications: cd-substituents on a carbon atom allow its selective dehydrodimerization. Olefines with geminal and thus cross-conjugated cd-substituents are “radicophilic” and permit twofold carbon radical addition. cd-Substituted olefines are useful antioxidants, polymerization inhibitors and are promising agents in the control of biological radical reactions. Generally, many reactions of cd-substituted molecules appear to involve radicals. 相似文献
8.
Valentino J. Stella Venkatramana M. Rao Erika A. Zannou 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):29-33
The purpose of this paper is to share some recent observations on the pharmaceuticaluses and properties of Captisol® or SBE7M--CD in controlled porosity osmotic pump tablets (CP-OPT) and the underlying mechanism/sthat lead to apparent zero-order drug release pattern. It would have been simple toattribute the apparent zero-order release mechanism/s of poorly water-soluble drugsfrom CP-OPTs and pellets utilizing Captisol®as both a solubilizing andosmotic agent, to purely osmotic and diffusional components. However, the mechanismmay be more related to a counterbalancing of physical properties as the concentration of Captisol®changes within the matrix. Specifically, the initial concentration of Captisol®within a core is 0.3–0.4M. When this drops to lower values an osmotic pressure drop occurs across the membrane. Therefore, drug release should not follow apparent zero-order kinetics if all the drug is solubilized. However, as the viscosity within the tablet also drops, the apparent diffusion coefficient of both Captisol® and drug increases. Therefore, it appears that there is an initial resistance (hydraulic pressure) to fluid flow from the tablet through the rate-limiting microporous membrane. This resistance decreases so that even as osmotic pressure and concentration differences drop with time, counterbalancing faster release occurs. Osmotic driving force appears to be the most important initial driving force but a diffusional component becomes more significant with time. 相似文献
9.
(Z, E)-9, 11-Tetradecadienyl-l-acetate (1), a major component of the sex pheromone of Spodoptera litura (F.), and (Z, E}-9, 11-pentadecadienyl-1-acetate (2) were synthesized by the Wittig reaction between (E)-2-alkenal (3) and the ylid derived from 9-hydroxynonyltriphenylphosphonium bromide (4). 相似文献
10.
The Hexagallane [Ga6{SiMe(SiMe3)2}6] and the closo‐Hexagallanate [Ga6{Si(CMe3)3}4 (CH2C6H5)2]2— — the Transition to an Unusual precloso‐Cluster The closo hexagallanate [Ga6R4(CH2Ph)2]2— (R = SitBu3) as well as the hexagallane Ga6R6 (R = SiMe(SiMe3)2) with only six cluster electron pairs were isolated from reactions of “GaI” with the corresponding silanides. The structure of the latter is derived from an octahedron by a Jahn‐Teller‐distortion and is different from the capped trigonal bipyramidal one expected by the Wade‐Mingos rules. Both compounds were characterized by X‐ray crystallography. The bonding is discussed with simplified Ga6H6 and Ga6H62— models via DFT methods. 相似文献