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1.
In this research article, we describe the synthesis and characterization of mononuclear and dinuclear Cu complexes bound by a family of tridentate redox-active ligands with tunable H-bonding donors. The mononuclear Cu-anion complexes were oxidized to the corresponding “high-valent” intermediates by oxidation of the redox-active ligand. These species were capable of oxidizing phenols with weak O−H bonds via H-atom abstraction. Thermodynamic analysis of the H-atom abstractions, which included reduction potential measurements, pKa determination and kinetic studies, revealed that modification of the anion coordinated to the Cu and changes in the H-bonding donor did not lead to major differences in the reactivity of the “high-valent” CuY complexes (Y: hydroxide, phenolate and acetate), which indicated that the tridentate ligand scaffold acts as the H+ and e− acceptor. 相似文献
2.
Maxime Mourer 《Tetrahedron letters》2006,47(12):1895-1899
New calixarene-based bis-bipyridyl podands incorporating two sodium (4-oxo)-butanoate or four sodium carboxymethyl groups at the upper rim were synthesised and fully characterised. The (4-oxo)-butanoate derivative bearing unsubstituted bipyridyl arms was not soluble in water at neutral pH, while its 4,4′-dicarboxylate analogue was perfectly soluble, as were the carboxymethyl derivatives. The association of water solubility to the chelating behaviour of the bipyridyl subunits resulted in the ability to complex the unstable copper(I) cation in water, even in the presence of bovine serum albumin. 相似文献
3.
This paper studies the application of the continuous sensitivity equation method (CSEM) for the Navier–Stokes equations in the particular case of shape parameters. Boundary conditions for shape parameters involve flow derivatives at the boundary. Thus, accurate flow gradients are critical to the success of the CSEM. A new approach is presented to extract accurate flow derivatives at the boundary. High order Taylor series expansions are used on layered patches in conjunction with a constrained least‐squares procedure to evaluate accurate first and second derivatives of the flow variables at the boundary, required for Dirichlet and Neumann sensitivity boundary conditions. The flow and sensitivity fields are solved using an adaptive finite‐element method. The proposed methodology is first verified on a problem with a closed form solution obtained by the Method of Manufactured Solutions. The ability of the proposed method to provide accurate sensitivity fields for realistic problems is then demonstrated. The flow and sensitivity fields for a NACA 0012 airfoil are used for fast evaluation of the nearby flow over an airfoil of different thickness (NACA 0015). Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
4.
Elizabeth M. Holt Balawant S. Joshi Dilip H. Gawad S. William Pelletier 《Journal of chemical crystallography》1990,20(3):261-264
The crystal and molecular structure of 1-ethyl-4-methoxy-9H-pyrido[3,4b]indole (crenatine) carbonate C14H14N2O·H2CO3, (MS, m/z 226)M
R
288.3, a-carboline alkaloid, has been determined from X-ray diffraction data. The compound crystallizes in the space group Pbca with cell parameters:a=11.616(4),b=18.450(8),c=12.992(5)Å,V=2784(2)Å3,Z=8,D
calc=1.375 g cm–3, (MoK)=0.71069Å,(Mo K)=0.94 cm–1,F(000)=1216,R/R
w
=8.2/10.3% for 1099 reflections. The ring system of the-carboline nucleus is planar. The title compound shows a two center hydrogen bond between the indole N-H group and the oxygen atom of a carbonate group. The structure does not display hydrogen bonding between-carboline groups but rather a bonding network involving the carbonate group. 相似文献
5.
Maxime Gouleau 《Annals of Global Analysis and Geometry》1987,5(3):217-259
Soient G une alébre de Lie nilpotente stratifée de rang 2, une sous-algébre de G, 0, la représentation de G dans l'espace L
2( \ G) indiute par le caractére trivial C, P un opérateur homogène appartenant à l'algébre universelle enveloppante (complexifiée) U(G) tel que l'opérateur 0, (P) soit hypoelliptique maximal. Cet opérateur peut s'exprimer par une intégrale dépendant de la restriction du symbole p de P au sousensemble = G · décrit par les orbites des éléments de dans la représentation contragrédiente de G dans G
*.Une algèbre de symboles définis sur est construite et permet de déterminer une paramétrixe de 0, (P); des résultats de réguralité de cet opérateur dans des espaces de Sobolev adaptés sont ensuite obtenus. 相似文献
6.
A classical electrostatic polarization scheme using the additive distribution procedure has been applied to determine the longitudinal polarizability of an all-trans hexatriene molecule in an infinite stretched fiber. The parameters have been derived from ab initio CPHF/6-31G calculations and the electrostatic scheme has been validated via comparison with ab initio results on small clusters. Upon packing the polarizability of all-trans hexatriene increases by 7%. This small increase results from the balance between the enhancement of the polarizability due to collinear packing and the reduction associated with lateral packing. 相似文献
7.
A solid phase tri-orthogonal protection/cleavage strategy that uses acidic, basic, and neutral conditions is described. Strategically protected alpha-azido-gamma-9-fluorenylmethyl-L-glutamate (1) and alpha-azido-epsilon-N-Fmoc-L-lysine (2) were incorporated into growing peptides on Wang resin using a novel azide protection strategy. These residues, separated by 1-3 monomers, were deprotected at the side chains and cyclized via lactam formation. The N-terminus was further functionalized to extend the chain. This method represents a straightforward protocol for peptide cyclization on solid support. 相似文献
8.
Hofmann A Pelletier M Michot L Stradner A Schurtenberger P Kretzschmar R 《Journal of colloid and interface science》2004,271(1):163-173
Hydrous ferric oxides (HFO) are efficient sorbents for inorganic and organic pollutants and therefore have great potentials in environmental science and engineering applications. Freezing and thawing of HFO suspensions leads to the formation of dense HFO aggregates. It facilitates the handling and increases the drying rate of HFO. In this study, we used a combination of pycnometry, gas adsorption (N(2) gas, water vapor), and small-angle neutron scattering (SANS) to characterize the porosity and pore size distribution of dense HFO aggregates formed by freezing dialyzed HFO suspensions at -25 degrees C and thawing them at room temperature. The crystallinity of the HFO, which was a 2-line ferrihydrite, was not affected by this treatment. Wet sieving and laser diffraction analysis showed that the dense HFO aggregates had a unimodal size distribution with an average diameter of 235+/-35 microm. Increasing the freezing rate by cooling with liquid N(2) (-196 degrees C) resulted in much smaller aggregates with an average diameter of 20 microm. Adding NaNO(3) electrolyte to the HFO suspensions prior to freezing also resulted in the formation of smaller aggregates. The dense HFO aggregates formed at -25 degrees C had a porosity of 0.73+/-0.02 ll(-1). SANS revealed a unimodal size distribution of pores, with an average pore diameter of 2.0 nm. The diameter of the HFO crystallites was estimated by transmission electron microscopy to be 1.9+/-0.5 nm. Geometrical considerations taking into account the unit particle and average pore size suggest that the crystallites retain 1-2 layers of hydration water during the coagulation induced by freezing. Analysis by N(2) gas adsorption showed that drying the dense HFO aggregates induced a reduction in porosity by about 25% and shifted the pore size distribution to smaller diameters. Rewetting during water vapor adsorption did not induce significant changes of the aggregate structure. The specific surface area of the dry HFO aggregates was between 320 and 380 m(2)g(-1). 相似文献
9.
In this paper, the transport of Cu(II) in the presence of lipophilic Cu(II) organic complexes through permeation liquid membranes (PLMs) have been investigated. In natural waters, small organic compounds, which form liposoluble neutral complexes with Cu(II), are potentially toxic and bioavailable. Hence, to understand the role of liposoluble Cu(II) complexes in natural waters, four organic ligands: phthalic acid, bipyridyl, pyrocatechol and hydroxyquinoline, which form uncharged or lipophilic Cu(II) complexes, were tested. The results showed that the transport of lipophilic Cu(II) complexes through PLM depends on the lipophilicity of the complex. Applications of PLMs in natural waters are presented. 相似文献
10.
This paper reports the synthesis of several 11,14-dimethoxydeoxypodocarpic acid derivatives from (+)-podocarpic acid. The synthesis of the naturally occurring sesquiterpene, (+)-winterin, from Drimys winteri illustrates a synthetic application of the 11,14-dimethoxy intermediates and establishes the absolute configuration for winterin. 相似文献