Hydrogen bonding interactions between indole and benzenoid-pi-bases

The NH-pi interactions of indole with benzene, naphthalene, phenanthrene, toluene, m-xylene, and mesitilene, in carbon tetrachloride solutions, have been studied by Fourier transform infrared spectroscopy. The experiments, carried out on the NH stretching band of indole, prove the formation of 1:1 complexes in which the NH bond of indole is engaged. The NH frequency shifts are independent of the number of rings in the base, but they progressively increase as the electron density is enhanced by methylation. The association constants increase with the increase of both, the number of rings and the methyl groups on the base. At higher base concentrations, further shifts on the free NH and associated bands indicate the formation of 1:2 complexes, which suggest hybride NH-pi and van der Waals interactions between one indole ring and two benzene acceptor molecules.     

CF2HCI在金属钨表面上的反应动力学

The unimolecular reaction of CF_2HCl on W filament has been studied. This reaction shows zero order at rather high pressure. The temperature threshold is about 440 ℃. The apparent activation energy of this reaction is 119.7 kJ mol~(-1) which is about a half of the activation energy for homogeneous unimolecular reaction of CF_2HCl, 233.5 kJ mol~(-1).     

Dichloro and alkylchloro gallium derivatives of dichalcogenoimidodiphosphinate ligands: isolation of a spirogallium cation

Dichloro and chloromethyl Ga(III) complexes of general formulae [XClGa-eta2-{R2P(E)NP(E'R'2-E,E'}](X = Cl, R, R'= Ph, E, E'= O (1), S (2), Se (3); R = Ph, R'= OEt, E = O, E'= S (4); R = Me, R'= Ph, E, E'= S (5) and X = Me, E, E'= O (6), S (7), Se (8)) were synthesised by either metathesis reactions between GaCl3 and the potassium salt of the ligand (X = Cl) or by methane eliminations from in situ prepared GaMe2Cl and the protonated ligands LH (X = Me). Redistribution reaction of (3) in either CDCl3 or THF afforded the solvent-free tetracoordinate gallium spirocycle cation [Ga-{eta2-{Ph2P(Se)NP(Se)Ph2-Se,Se'})2]+ (9+). The molecular structures of complexes 2, 4, 5, 7 and 9(+) show non-planar gallacycle rings.     

Increased enantioselectivity in the addition of diethylzinc to benzaldehyde by the use of chiral ligands containing the alpha-phenylethylamino group in combination with achiral ligands

Chiral ligands (S,S)-1, (S,S)-2, (S,S)-3, (S)-4, (S)-5, (S,S)-6, (S,S)-7, and (S,S)-8 turned out to be effective promoters in the enantioselective addition of diethylzinc to benzaldehyde. Interestingly, diamine (S,S)-3 and amino alcohols (S)-5 and (S,S)-7 induce the preferential formation of carbinol (R)-10 (unlike stereoinduction) whereas amido analogues (S,S)-2, (S)-4, and (S,S)-6 favor (S)-10 (like stereoinduction). Molecular modeling at the semiempirical PM3 level provided a reasonable interpretation based on conformational effects in the corresponding transition structures. Combinations of chiral ligands 1-8 with an achiral, flexible ligand (9) gave rise to an activated catalytic system that resulted in faster and higher yielding reactions. Furthermore, substantial increases in the observed enantiomeric excesses of product 10 confirmed the relevant role of achiral bis(sulfonamide) 9 as activator and "chiral environment amplifier".     

A continuous flow system design for simultaneous determination of heavy metals in river water samples

A new design of a continuous flow system applied to the simultaneous determination of the concentration of zinc(II), cadmium(II), lead(II), copper(II), nickel(II), cobalt(II) and chromium(VI) in river water is described. A flow cell made in the laboratory, which has been patented, based on a 'wall-jet' configuration with a three-electrode system is described. Optimum conditions for the determination of the metal ions are reported. The detection limits and relative standard deviation values were 4.01x10(-9) M and 0.078 for Zn(II), 1.76x10(-10) M and 0.056 for Cd(II), 4.69x10(-10) M and 0.134 for Pb(II), 2.29x10(-10) M and 0.138 for Cu(II), 1.61x10(-9) M and 0.093 for Ni(II), 1.91x10(-9) M and 0.113 for Co(II), and 1.35x10(-9) M and 0.081 for Cr(VI). The procedure was applied to a sample of water from the Arlanzón river and the results were compared with inductively coupled mass plasma spectrometry (ICP-MS) as reference method. The final aim of this work is to design a flow system, which can be automated.     

Surface-functionalized latex particles as controlling agents for the mineralization of zinc oxide in aqueous medium

Polystyrene latex particles modified at the surface with different hydrophilic functional groups were prepared by miniemulsion polymerization and used as controlling agents in the crystallization of zinc oxide from aqueous medium. The effects of the chemical nature of the surface functionalization and the latex concentration on the crystal growth, morphology, and crystalline structure of the resulting zinc oxide were analyzed. Micro- and submicrosized crystals with a broad variety of morphologies depending on the functionalization were obtained. Among the different latexes studied, the acrylic-acid-derived particles were shown to be a convenient system for further quantitative investigations. In this case, as the additive concentration increases, the length-to-width ratio (aspect ratio) of the crystals decreases systematically. Preferential adsorption of the latex particles onto the fast-growing faces {001} of ZnO is assumed to follow a Langmuir-type isotherm, and interaction of the adsorbed particles with the growth centers will reduce the growth rate in [001]. This leads to a quantitative relationship linking the aspect ratio to the latex concentration at constant diameter and surface chemistry of the latex. The dependence of the aspect ratio on charge density of the latex can also be modeled by an algorithm in which attractive forces between the latex particle and the ZnO surface are balanced against repulsive forces of an osmotic nature. The latter are associated with the confined volume between the crystal and latex particle surfaces.     

C波段微波低相位噪声介质振荡源

介绍了微波低相位噪声介质振荡器的设计方法。就影响介质振荡器相位噪声的因素进行了讨论,从谐振回路有载Q值、有源器件、增益压缩量、电路模式等几个方面提出了降低相位噪声的方法,并给出了一个C波段微波低相噪振荡器的设计实例。测试结果表明:该振荡器工作频率3 900 MH z,输出功率大于10 dBm,相位噪声达到-102 dB c/H z@1 kH z;-128 dB c/H z@10 kH z。     

Temperature and metal composition dependence of lateral photovoltaic effect in Al-Alq3/SiO2/Si structures

A series of Al=-（Alq3）l-x granular films is prepared on Si wafer with native oxide layer using co-evaporation technique. Large lateral photovoltaic effect （LPE） is observed, with an optimal LPV sensitivity of 75 mV/mm in x=0.35 sample. The dependence of LPE on temperature and A1 composition is investigated, and the possible mechanism is discussed.