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排序方式: 共有1117条查询结果,搜索用时 290 毫秒
941.
942.
Campidelli S Ballesteros B Filoramo A Díaz DD de la Torre G Torres T Rahman GM Ehli C Kiessling D Werner F Sgobba V Guldi DM Cioffi C Prato M Bourgoin JP 《Journal of the American Chemical Society》2008,130(34):11503-11509
We describe the functionalization of single-wall carbon nanotubes (SWNTs) with 4-(2-trimethylsilyl)ethynylaniline and the subsequent attachment of a zinc-phthalocyanine (ZnPc) derivative using the reliable Huisgen 1,3-dipolar cycloaddition. The motivation of this study was the preparation of a nanotube-based platform which allows the facile fabrication of more complex functional nanometer-scale structures, such as a SWNT-ZnPc hybrid. The nanotube derivatives described here were fully characterized by a combination of analytical techniques such as Raman, absorption and emission spectroscopy, atomic force and scanning electron microscopy (AFM and SEM), and thermogravimetric analysis (TGA). The SWNT-ZnPc nanoconjugate was also investigated with a series of steady-state and time-resolved spectroscopy experiments, and a photoinduced communication between the two photoactive components (i.e., SWNT and ZnPc) was identified. Such beneficial features lead to monochromatic internal photoconversion efficiencies of 17.3% when the SWNT-ZnPc hybrid material was tested as photoactive material in an ITO photoanode. 相似文献
943.
Fernández-Ibáñez MA Maciá B Minnaard AJ Feringa BL 《Chemical communications (Cambridge, England)》2008,(22):2571-2573
Chiral tertiary alcohols were obtained with good yields and enantioselectivities via a catalytic Reformatsky reaction with ketones, including the challenging diaryl ketones, using chiral BINOL derivatives. 相似文献
944.
Bandrés I Giner B Artigas H Royo FM Lafuente C 《The journal of physical chemistry. B》2008,112(10):3077-3084
A comprehensive thermophysical study of isomeric room-temperature ionic liquids n-butyl-3-methyl-pyridinium tetrafluoroborate and n-butyl-4-methyl-pyridinium tetrafluoroborate has been performed. This paper reports various experimental data including density, speed of sound, refractive index, surface tension, isobaric molar heat capacity, and kinematic viscosity. From the experimental results, coefficients of thermal expansion, dynamic viscosities and molar refractions of the studied ionic liquids have been determined. Results have been analyzed paying special attention to the different features of the isomers and their structural differences. Several theories and empirical relations have been applied in order to predict physical properties of ionic liquids. A good agreement between experimental and calculated data has been found. Furthermore, a study about the versatility and application of the different relationships has been carried out finding that in general density and coefficients of thermal expansion can be estimated with relatively good accuracy. 相似文献
945.
Bandrés I Giner B Gascón I Castro M Lafuente C 《The journal of physical chemistry. B》2008,112(39):12461-12467
The room temperature ionic liquid n-butyl-3-methylpyridinium dicyanamide has been characterized. Physicochemical properties such as density, speed of sound, refractive index, surface tension, and kinematic viscosity of the studied liquid have been experimentally measured in a wide range of temperatures. From results, coefficients of thermal expansion, molar refractions, dynamic viscosities and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been derived. We have analyzed the achieved results for evaluating the effect of the anionic structure in these properties, getting interesting results which lead us to a better understanding of the behavior of the ions in the fluids. Moreover, thermal properties of several pyridinium-based ionic liquids have been investigated. Finally, from both dynamic viscosity values and glass transition temperature of the studied liquids, a detailed analysis of the behavior in fragility terms has been performed. 相似文献
946.
Vicente E Villar R Burguete A Solano B Ancizu S Pérez-Silanes S Aldana I Monge A 《Molecules (Basel, Switzerland)》2008,13(1):86-95
The unexpected substitution of fluorine atoms and phenoxy groups attached to quinoxaline or benzofuroxan rings is described. The synthesis of 2-benzyl- and 2-phenoxy-3-methylquinoxaline 1,4-di-N-oxide derivatives was based on the classical Beirut reaction. The tendency of fluorine atoms linked to quinoxaline or benzofuroxan rings to be replaced by a methoxy group when dissolved in an ammonia saturated solution of methanol was clearly demonstrated. In addition, 2-phenoxyquinoxaline 1,4-di-N-oxide derivatives became 2-aminoquinoxaline 1,4-di-N-oxide derivatives in the presence of gaseous ammonia. 相似文献
947.
Lima LM Vicente E Solano B Pérez-Silanes S Aldana I Monge A 《Molecules (Basel, Switzerland)》2008,13(1):78-85
The unexpected tendency of amines and functionalized hydrazines to reduce ethyl 3-phenylquinoxaline-2-carboxylate 1,4-di-N-oxide (1) to afford a quinoxaline 1c and mono-oxide quinoxalines 1a and 1b is described. The experimental conditions were standardized to the use of two equivalents of amine in ethanol under reflux for two hours,with the aim of studying the distinct reductive profiles of the amines and the chemoselectivity of the process. With the exception of hydrazine hydrate, which reduced compound 1 to a 3-phenyl-2-quinoxalinecarbohydrazide derivative, the amines only acted as reducing agents. 相似文献
948.
949.
We present a novel approach for the ultra-rapid direct patterning of complex three-dimensional, stacked polystyrene (PS) microfluidic chips. By leveraging the inherent shrinkage properties of biaxially pre-stressed thermoplastic sheets, microfluidic channels become thinner and deeper upon heating. Design conception to fully functional chips can thus be completed within minutes. 相似文献
950.
Gutiérrez MM Alluisetti GB Olabe JA Amorebieta VT 《Dalton transactions (Cambridge, England : 2003)》2008,(37):5025-5030
The kinetics of the reaction between aqueous solutions of Na(2)[Fe(CN)(5)NO].2H(2)O (sodium pentacyanonitrosylferrate(ii), nitroprusside, SNP) and MeN(H)OH (N-methylhydroxylamine, MeHA) has been studied by means of UV-vis spectroscopy, using complementary solution techniques: FTIR/ATR, EPR, mass spectrometry and isotopic labeling ((15)NO), in the pH range 7.1-9.3, I = 1 M (NaCl). The main products were N-methyl-N-nitrosohydroxylamine (MeN(NO)OH) and [Fe(CN)(5)H(2)O](3-), characterized as the [Fe(CN)(5)(pyCONH(2))](3-) complex (pyCONH(2) = isonicotinamide). No reaction occurred with Me(2)NOH (N,N-dimethylhydroxylamine, Me(2)HA) as nucleophile. The rate law was: R = k(exp) [Fe(CN)(5)NO(2-)] x [MeN(H)OH] x [OH(-)], with k(exp) = 1.6 +/- 0.2 x 10(5) M(-2) s(-1), at 25.0 degrees C, and DeltaH(#) = 34 +/- 3 kJ mol(-1), DeltaS(#) = -32 +/- 11 J K(-1) mol(-1), at pH 8.0. The proposed mechanism involves the formation of a precursor associative complex between SNP and MeHA, followed by an OH(-)-assisted reversible formation of a deprotonated adduct, [Fe(CN)(5)(N(O)NMeOH)](3-), and rapid dissociation of MeN(NO)OH. In excess SNP, the precursor complex reacts through a competitive one-electron-transfer path, forming the [Fe(CN)(5)NO](3-) ion with slow production of small quantities of N(2)O. The stoichiometry and mechanism of the main adduct-formation path are similar to those previously reported for hydroxylamine (HA) and related nucleophiles. The nitrosated product, MeN(NO)OH, decomposes thermally at physiological temperatures, slowly yielding NO. 相似文献