排序方式: 共有77条查询结果,搜索用时 31 毫秒
51.
Complexes (R3P)2PtF2 were prepared by reaction of the corresponding diiodo precursors with AgF in dichloromethane. The intermediate formation of trans- and cis-(R3P)2Pt(I)F was also observed. All fluoro complexes demonstrate a strong preference for the cis-configuration (R = Ph or Et) unless a bulky phosphine ligand is used (R = i-Pr), in which case the trans complex was observed. The Pt(IV) difluoro compounds (R3P)2Ar2PtF2 were obtained by reacting the Pt(II) diaryl precursors with XeF2. The fluoro ligands are located in the trans-position relative to the aryl groups in the overall octahedral environment. The representative Pt(II) and Pt(IV) difluoro complexes were characterized by X-ray crystallography. All fluoro compounds react rapidly with chlorotrimethylsilane to give the corresponding chloro complexes. The Pt(IV) difluorides are remarkably stable in the C-C reductive elimination reaction, relative to their dichloro analogs which reductively eliminate diaryl within several hours at 45 degrees C in N-methylpyrrolidone. It was found that phosphine dissociation from the octahedral Pt(IV) complex is essential for the reductive elimination reaction to take place, the difluoro complex being kinetically stable even at 60 degrees C. 相似文献
52.
A new method has been developed which allows determination of the coagulation coefficient of two oppositely charged particles experimentally. For this purpose, quasi-monodisperse particles of different sizes and morphology were used to study the influence of different parameters on the coagulation coefficient. A good agreement between experimental results and the classic Fuchs' theory was obtained when including a method accounting for particle nonsphericity. In experiments with polydisperse bipolarly charged aerosols, no principal differences to uncharged aerosols were found when a dimensionless representation was used. Changes in particle number concentration and geometric mean diameter can be described by simple empirical expressions. 相似文献
53.
54.
Optimal solutions of Linear Programming problems may become severely infeasible if the nominal data is slightly perturbed.
We demonstrate this phenomenon by studying 90 LPs from the well-known NETLIB collection. We then apply the Robust Optimization
methodology (Ben-Tal and Nemirovski [1–3]; El Ghaoui et al. [5, 6]) to produce “robust” solutions of the above LPs which are
in a sense immuned against uncertainty. Surprisingly, for the NETLIB problems these robust solutions nearly lose nothing in
optimality.
Received: July 1999 / Accepted: May 2000?Published online July 20, 2000 相似文献
55.
Christian Helgert Thomas Pertsch Carsten Rockstuhl Ekaterina Pshenay-Severin Christoph Menzel Ernst-Bernhard Kley Arkadi Chipouline Christoph Etrich Uwe Huebner Andreas Tuennermann Falk Lederer 《中国光学与应用光学文摘》2010,(1)
In this contribution we review our latest achievements of combined experimental and theoretical studies to tailor the properties of optical metamaterials(MMs) at will. We give three examples of metamaterial designs that have been realized by means of electron-beam lithography and whose spectroscopic characteristics have been comprehensively investigated. In every case, our experiments are complemented by rigorous numerical simulations. Particular emphasis is put on the significance of such tailored effectiv... 相似文献
56.
Berezovski Arkadi Yildizdag M. Erden Scerrato Daria 《Continuum Mechanics and Thermodynamics》2020,32(3):569-588
Continuum Mechanics and Thermodynamics - In this paper, elastic wave propagation in a one-dimensional micromorphic medium characterized by two internal variables is investigated. The evolution... 相似文献
57.
58.
Matthias Keck Santina Hoof Varun Rawat Arkadi Vigalok Christian Limberg 《无机化学与普通化学杂志》2020,646(13):904-908
A calix[4]arene, in which two of the phenol functions are replaced by pyrazole units, [H2(bpzCal)], was investigated as a ligand for Cu+, Ag+ and Au+ ions. Using [Cu(MeCN)4]BF4 and AgSbF6 as the precursors, complexes [MH2(bpzCal)]X (M = Cu, X = BF4; M = Ag, X = SbF6) were formed, where the calixarene ligands adopt a 1,3-alternate structure and the metal ions are coordinated linearly by the two pyrazolyl donors. [CuH2(bpzCal)]BF4 displayed a – for copper(I) complexes – unusual stability towards O2, which is due to the steric protection of the CuI center. By contrast a dinuclear copper(I) complex [Cu2(bpzCal)] that was obtained through treatment of [H2(bpzCal)] with two equivalents of Cu(HMDS) is rather sensitive towards O2. The preparation of a gold complex required the employment of a gold precursor, which contains one labile and one stabilizing neutral ligand, namely [(PPh3)Au(NCMe)]SbF6, which led to the formation of [(PPh3)AuH2(bpzCal)]SbF6. In this complex [H2(bpzCal)] acts only as a monodentate ligand for the gold center. Taken together, the results demonstrate the potential of [H2(bpzCal)] in providing rather different coordination spheres for metal ions. 相似文献
59.
Arkadi V. Eremenko Alexander Makower Frieder W. Scheller 《Fresenius' Journal of Analytical Chemistry》1995,351(8):729-731
A new enzyme amplification scheme based on the measurement of the pH-change generated in the laccase/glucose dehydrogenase substrate recycling reaction has been established. Quinone species formed after oxidation of diphenols by laccase are reduced by glucose dehydrogenase in the presence of glucose. Catalytic oxidation of glucose to gluconic acid via gluconolactone leads to a pH-decrease. The utility of the very simple pH-sensitive antimony electrode for monitoring the bienzyme reaction has been shown. The detection limit for norepinephrine and p-aminophenol measured by the bienzyme-modified antimony electrode was 1 nmol/L in the presence of glucose. The enhancement in sensitivity and analytical applications of the proposed scheme are discussed.
Permanent address: Department of Biosensors, Research Center for Molecular Diagnostics and Therapy, Simpheropolsky Blvd. 8, 113149 Moscow, Russia 相似文献
60.
[reaction: see text] Bimetallic alkylzinc calixarene inclusion complexes were prepared and used in the ring-opening polymerization of L-lactide. Polymers with high molecular weight and a low degree of polydispersity were obtained. 1H NMR and diffusion NMR experiments suggest that a single-site mechanism is operative. 相似文献