排序方式: 共有68条查询结果,搜索用时 15 毫秒
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Jonathan L. Sessler Patricia J. Melfi Anne E.V. Gorden Doris K. Ford C. Drew Tait 《Tetrahedron》2004,60(49):11089-11097
Hexaphyrin(1.0.1.0.0.0) (isoamethyrin) undergoes a significant color change in the presence of UO22+, PuO22+, and NpO22+. The complexation of the first of these dioxo actinide cations was studied in semi-quantitative fashion in 1:1 MeOH-CH2Cl2. Under these conditions, the detection limit for UO22+ was found to be ca. 5.8 ppm by naked eye monitoring and <28 ppb by UV-vis spectroscopy. Isoamethyrin does not undergo a color change in the presence of most transition metals or when exposed to Gd(III). Isoamethyrin thus constitutes an attractive alternative to 2,2′(1,8-dihydroxy-3,6-disulfonaphthylene-2,7-bisazo)-bisbenzenarsonic acid (AzIII) and 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (BrPADAP), systems currently used as actinide cation sensors. 相似文献
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Hardman NJ Power PP Gorden JD Macdonald CL Cowley AH 《Chemical communications (Cambridge, England)》2001,(18):1866-1867
Examples of compounds with gallium-boron donor-acceptor bonds, HC[MeC(2,6-pri2C6H3)N]2Ga-->B(C6F5)3 3 and (eta 5-C5Me5)Ga-->B(C6F5)3 4 have been prepared by treatment of the free gallanediyls with B(C6F5)3; the structures of both compounds were determined by X-ray crystallography. 相似文献
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The synthesis of carbonyl compounds by oxidation of alcohols is a key reaction in organic synthesis. Such oxidations are typically conducted using catalysts featuring toxic metals and hazardous organic solvents. Considering green and sustainable chemistry, a copper(II) complex of sulfonated 2-quinoxalinol salen (sulfosalqu) has been characterized as an efficient catalyst for the selective oxidation of propargylic, benzylic, and allylic alcohols to the corresponding carbonyl compounds in water when in combination with the oxidant tert-butyl hydroperoxide. The reactions proceed under mild conditions (70 °C in water) to produce yields up to 99% with only 1 mol % of catalyst loading. This reaction constitutes of a rare example of propargylic alcohol oxidation in water, and it makes this process greener by eliminating the use of hazardous organic solvents. Excellent selectivity was achieved with this catalytic protocol for the oxidation of propargylic, benzylic, and allylic alcohols over aliphatic alcohols. The alcohol oxidation is thought to go through a radical pathway. 相似文献
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A. G. Sim o L. G. Guimar es Gorden Videen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):777-786
We show that dielectric spherical and cylindrical particles contaminated with a metallic inclusion have similar spectral resonant behavior. Both geometries show resonance suppression as the position of the inclusion varies. Moreover, it was theoretically observed that the spherical particle suppresses a resonant mode earlier than the cylindrical one. Based on semi-classical arguments, a physical interpretation of this fact is given. In addition, a comment is also made regarding Wiscombe's criteria for estimating the size of the coefficient matrix used to solve the truncated non-homogeneous set of linear equations related to this problem. 相似文献
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Coates CM Hagan K Mitchell CA Gorden JD Goldsmith CR 《Dalton transactions (Cambridge, England : 2003)》2011,40(16):4048-4058
Iron and manganese complexes with derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen) have previously been found to be efficient catalysts for hydrocarbon oxygenation. Methylation can potentially impact the conformation of the ligand around the metal center and the electronic character of the bound metal ion; each of these, in turn, impacts reactivity. Reported are mononuclear manganese(II) and iron(II) compounds with bispicen and five increasingly methylated derivatives. The extent and sites of methylation strongly impact the optical and electrochemical properties of the manganese and iron complexes. Increased methylation is correlated with more positive M(III/II) reduction potentials. Structural analysis of the Mn(II) series reveals two ligand conformations that have never been observed for the bispicen framework, cis-β and trans, in addition to the common cis-α conformation. (1)H NMR spectra of the structurally characterized iron compounds are consistent with mixtures of these conformers, suggesting that bispicen coordination is both more flexible and more dynamic than previously thought. 相似文献
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Evgenij Zubko Yuriy Shkuratov Michael Mishchenko Gorden Videen 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(12-13):2195-2206
We use the discrete dipole approximation (DDA) to perform electromagnetic scattering calculations of particles in a 3D volume. We adjust the spacing between the particles to change the volume densities of the scattering systems from approximately 10% to 100%. For very large volume densities, e.g. >50%, it is difficult to assign unambiguously whether the system is composed of a single heterogeneous particle or of multiple particles. Our calculations demonstrate optical effects attributable to multiple scattering in systems having volume densities as high as ~90%. This suggests that heterogeneities within naturally occurring particle systems can produce multiple-scattering effects. We also see evidence of very deep negative polarization branches (NPBs) (~?6%) that may have implications in interpreting polarization phase curves of cometary circumnuclear halos. 相似文献
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Andreas Eichhorn Nicole Grwe‐Kuska Andrea Liebscher Werner Rmisch Gorden Spangardt Isabel Wegner 《PAMM》2004,4(1):3-6
We present a mathematical model with stochastic input data for mean‐risk optimization of electricity portfolios containing several physical components and energy derivative products. The model is designed for the optimization horizon of one year in hourly discretization. The aim consists in maximizing the mean book value of the portfolio at the end of the optimization horizon and, at the same time, in minimizing the risk of the portfolio decisions. The risk is measured by the conditional value‐at‐risk and by some multiperiod extension of CVaR, respectively.We present numerical results for a large‐scale realistic problem adapted to a municipal power utility and study the effects of varying weighting of risk. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Using a Cu(II) 2-quinoxalinol salen complex as the catalyst and tert-butyl hydroperoxide (TBHP) as the oxidant, allylic activations of olefin substrates can be converted to the corresponding enones or 1,4-enediones. Excellent yields can be achieved (up to 99%) within a very short reaction time and with great tolerance for additional functional groups. Possible mechanistic pathways have been characterized using Raman spectroscopy, cyclic voltammetry, and theoretical calculations. 相似文献