An approach to the tricyclic core of madangamines based upon a biogenetic scheme

[reaction: see text] A short synthesis of intermediates possessing the tricyclic core of natural madangamines, bioactive alkaloids found in marine sponges, is described. The key reaction entails the condensation of the sodium salt of diethylacetonedicarboxylate with a dihydropyridinium salt derivative. This new approach is modeled on a biogenetic proposal linking madangamines to ircinals, related alkaloids occurring in sponges of the same order.     

Synthesis, characterization and luminescence study of dimethyl(β-ketoiminato)gallium (-indium) complexes: crystal structure of dimethyl[1-phenyl-3-N-(4-methoxyphenylimino)-1-butanonato]gallium

Six dimethylgallium (indium) complexes of type Me₂ML [M = Ga, L = 1-phenyl-3-N-(phenylimino)-1-butanonato (1), 1-phenyl-3-N-(p-methoxyphenylimino)-1-butanonato (2), 1-phenyl-3-N-(o-chloro phenylimino)-1-butanonato (3); M = In, L = 1-phenyl-3-N-(phenyl imino)-1-butanonato (4), 1-phenyl-3-N-(p-methoxyphenylimino)-1-butanonato (5), 1-phenyl-3-N-(o-chlorophenylimino)-1-butanonato (6)] have been synthesized by reaction of trimethylgallium (indium) with appropriate 1-phenyl-3-N-(arylimino)-1-butanones. The complexes obtained have been characterized by elemental analysis, ¹H NMR, IR and mass spectroscopy. Structure of 2 has been determined by X-ray single-crystal analysis, in which Ga atom is four coordinated. Complexes 1-6 emit colors from blue to green (463-491 nm) when irradiated by UV light. The electroluminescent (EL) properties of 1-6 were examined by fabricating EL devices using 1-6 as emitter, respectively. The EL bands are located in the green region (509-522 nm).     

反应条件对Mo2C/Al2O3催化的POM制合成气的影响

考察了反应温度、气体空速和进料中CH4：O2比值对Mo2C／Al2O3催化的POM反应制合成气的影响．结果发现较高的温度具有较高的甲烷转化率、CO和H2的选择性；而在较低的温度下，对CO的选择性比对H2的影响更大．反应气体的空速较小时对于甲烷的转化率、CO和H2的选择性是有利的；而在较高的气体空速下，氢气的选择性则更低．进料中CH4：O2比值稍高于2：1时有利于获得高的甲烷转化率、CO和H2的选择性．并且还可以增加催化剂的稳定性．当CH4：O2比值低于2：1时．甲烷转化率、CO和H2选择性随反应的进行急剧下降．而当此比值调整到高于2：1时．转化率和选择件都可以得到恢复。     

Azido- or hydroxyl-capped half-cubanes containing Cp*Rh fragments: [Cp*3Rh3(mu-X)3(mu3-X)]2+ (X-=OH- or N3-)

Treatment of [Cp*Rh(H(2)O)(3)](OTf)(2) (1) with Me(3)SiNH-t-Bu in acetone gave a hydroxyl-capped half-cubane [Cp*(3)Rh(3)(mu-OH)(3)(mu(3)-OH)](OTf)(3)(t-BuNH(3)) (2). Slow diffusion of Me(3)SiN(3) in diethyl ether into compound in acetone produced an azido-capped half-cubane [Cp*(3)Rh(3)(mu-N(3))(3)(mu(3)-N(3))](OTf)(2) (3). On the other hand, treating 1 with Me(3)SiN(3) in acetone gave an azido-bridged, dinuclear rhodium(III) complex [Cp*Rh(mu-N(3))(OH(2))](2)(OTf)(2) (4). Complexes 2 and 3 represent the first azido- or hydroxyl-capped, incomplete cubane-type Rh clusters. Under appropriate conditions, complexes 2 and 3 could be converted to complex 4. The structures of all products were determined by X-ray diffraction.     

The adsorption and dissociation of O2 on Cu low-index surfaces

The extended LEPS of O(2)-Cu single crystal plane systems is constructed by means of 5-MP (the 5-parameter Morse potential). Both the adsorption and dissociation of O(2) on Cu low-index surfaces are investigated with extended LEPS in detail. All critical characteristics of the system that we obtain, such as adsorption geometry, binding energy, eigenvalues for vibration, etc., are in good agreement with the experimental results. Our calculated results suggest there are many differences between O(2)-Cu (110) and O(2)-Pd (110) systems. On a Cu (110) surface, O(2) adsorbs in a tilted configuration and there are two lowest energy dissociation channels along the [001] and [10] directions, respectively. We speculate that the adsorption geometry of O(2) on the metal surfaces relates to the lattice constant of metal. Meanwhile, We use the concepts of the molecular dissociation limit and the surface dissociation distance to analyze again the dissociation mechanism of the O(2) on the low-index surfaces.     

pH sensitivity of Si--C linked organic monolayers on crystalline silicon surfaces.

The electrochemical behavior of Si--C linked organic monolayers is studied in electrolyte-insulator-Si devices, under conditions normally encountered in potentiometric biosensors, to gain fundamental knowledge on the behavior of such Si electrodes under practical conditions. This is done via titration experiments, Mott-Schottky data analysis, and data fitting using a site-binding model. The results are compared with those of native SiO(2) layers and native SiO(2) layers modified with hexamethyldisilazane. All samples display pH sensitivity. The number of Si--OH groups on the alkylated samples is calculated to be less than 0.7 % of that of a pure SiO(2) insulator, which still causes a pH sensitivity of approximately 25 mV per pH unit in the pH range: 4-7. The alkylated samples hardly suffer from response changes during up- and down-going titrations, which indicates that very little oxide is additionally formed during the measurements. The pK(a) values of all samples with monolayers (4.0-4.4) are lower than that of native SiO(2) (6.0). The long-term drift (of approximately 1 mV h(-1)) is moderate. The results indicate that biosensors composed of alkylated Si substrates are feasible if a cross-sensitivity towards pH in the sensor signal is taken into account.     

三元稀土萃取分离工艺中有效分离系数的研究

本文通过计算机模拟计算,对恒定混合萃取比的三元稀土萃取分离工艺中有效分离系数的变化规律进行了研究,并在串级萃取理论的基础上提出了一种采用有效分离系数确定三元稀土萃取分离工艺参数的方法。     

NaCl(或KCl)-CH3OH-H2O体系的摩尔电导

CHaOH－HzO体系具有非常特殊的性质，同时在工业生产及临床治疗方面有着十分广泛的应用，文献中有大量地从不同角度就这类体系进行研究的报道．然而，就N3CI及KCI－CH30H－H20体系的电导研究而言，文献中仅有关干KCI－CH30H－H20（间隔20％CH30H）的部分研究工作．作为全面、系     

Rapid—In—situ Determination of Chromium （VI） in Water Using Modified Diphenylcarbazine with Citrate

In recent years, the determination of Cr (VI) has attracted great attention because of its toxicity to human, plants and animals1-5. Usually, in the industrial waste water, the concentration of Cr (VI) is relatively high and should be determined frequently. So, an accurate, quick, and convenient method for the measurement of Cr (VI) in environmental water, as well as in river, lake, sea and tap water, is of great importance. The method for determination of Cr (VI) by diphenylcarbazine …     

Phase separation of the reaction system induced by CO2 and conversion enhancement for the esterification of acetic acid with ethanol in ionic liquid

The effect of CO2 on the phase behavior of the reaction system and equilibrium conversion for esterification of acetic acid and ethanol in ionic liquid (1-butyl-3-methylimidazolium hydrogen sulfate, [bmim][HSO4]) was studied at 60.0 degrees C up to 15 MPa. It was demonstrated that there was only one phase in the reaction system in the absence of CO2. The reaction system underwent two-phase-->three-phase-->two-phase transitions with increasing pressure. The pressure of CO2 or the phase behavior of the system affected the equilibrium conversion of the reaction markedly. As the pressure was less than 3.5 MPa, there were two phases in the system, and the equilibrium conversion increased as pressure was increased. In the pressure range of 3.5-9.5 MPa, there existed three phases, and the equilibrium conversion increased more rapidly with increasing pressure. As the pressure was higher than 9.5 MPa, the reaction system entered another two-phase region and the equilibrium conversion was nearly independent of pressure. The total equilibrium conversion was 64% without CO2 and could be as high as 80% as pressure was higher than 9.0 MPa. The apparent equilibrium constants (K(x)) in different phases were also determined, showing that the K(x) in the middle phase or top phase was much greater than that in the bottom phase.