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排序方式: 共有328条查询结果,搜索用时 31 毫秒
71.
Ercan Bayram 《Journal of organometallic chemistry》2006,691(15):3267-3273
The labile complex W(CO)5(η2-btmse) undergoes replacement of bis(trimethylsilyl)ethyne, btmse, by triphenylbismuthine in cyclohexane solution at an observable rate in the temperature range of 35-50 °C yielding almost solely W(CO)5(BiPh3) as the final product. The kinetics of this substitution reaction was studied in cyclohexane solution by quantitative FT-IR spectroscopy. The substitution reaction obeys a pseudo-first-order kinetics with respect to the concentration of the starting complex. The observed rate constant, kobs, was determined at four different temperatures and three different concentrations of the entering ligand BiPh3 in the range 16.8-65.4 mM. From the evaluation of kinetic data a possible reaction mechanism was proposed in which the rate determining step is the cleavage of metal-alkyne bond in the complex W(CO)5(η2-btmse). A rate law was derived from the proposed mechanism. From the dependence of kobs on the entering ligand concentration, the rate constant k1 for the rate determining step was estimated at all temperatures. The activation enthalpy (106 ± 2 kJ mol−1) and the activation entropy (111 ± 6 J K−1 mol−1) were determined for this rate determining step from the evaluation of k1 values at different temperatures. The large positive value of the activation entropy is consistent with the dissociative nature of reaction. The large value of the activation enthalpy, close to the calculated tungsten-alkyne bond dissociation energy, also supports this dissociative rate-determining step of the substitution reaction. 相似文献
72.
73.
Ismail Ercan Filiz Ercan Cengiz Arc Orhan Atakol 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):m137-m138
A new tetranuclear CuII–HgII–HgII–CuII complex, [Cu2Hg2Cl4(C18H18N2O2)2], has been prepared by means of a copper complex found in the literature. The molecular structure of this complex was determined by X‐ray diffraction and the Cu–Hg–Hg–Cu chain was seen to be non‐linear. The change in magnetic susceptibility with temperature was recorded for this complex and observed to abide by the Curie–Weiss law. The coordination around the HgII ions is square pyramidal. The Cu?Hg bridging distance is 3.5269 (7) Å. 相似文献
74.
M. Oddone Z. Yegingil G. Bigazzi T. Ercan M. Özdogan 《Journal of Radioanalytical and Nuclear Chemistry》1997,224(1-2):27-38
Obsidian is a volcanic glass which is generally black, sometimes grey, brown, red or green in colour and characterised by a glassy appearance and conchoidal fractures. It is formed by the sudden cooling of the molten, generally acid magma with high water content. Obsidian was widely used for tool-making during prehistoric times. This work concems the chemical characterisation of obsidian occurrences from Northem, Central and Eastem Anatolia by Instrumental and Epithemal Neutron Activation Analysis for obtaining an accurate fingerprint for discrimination of potential natural sources of raw material that would permit tracing the origin of archaeological obsidian artefacts. 相似文献
75.
The novel (E,E)-dioxime 5,6:13,14-dibenzo-9,10-benzo(15-crown-5)-2,3-bis(hydroxyimino)-7,12-dioxo-1,4,8,11-tetraazacyclotetradecane (H2L) has been synthesized by the reaction of 4′,5′-diaminobenzo(15-crown-5) with N,N′-bis(2-carbomethoxyphenyl)diaminoglyoxime (1). Only mononuclear CoIII and RuII complexes with a metal/ligand ratio of 1:2 have been isolated. The cobalt(III) complex bridged with BF2+ is achieved with H-bonded cobalt(III) complex and borontrifluoride ethyl ether complex. The reaction of BF2 bridged cobalt(III) complex with bis(benzonitril)palladium(II) chloride gives a trinuclear complex. The structures of dioxime and its complexes are proposed according to elemental analyses, 1H and 13C-NMR, IR and mass spectral data. 相似文献
76.
Murat Çelik Cemalettin Alp M. Serdar Gültekin Metin Balci 《Tetrahedron letters》2006,47(22):3659-3663
1,2- and 1,3-Bis(trifluoroacetoxy) alcohols are easily obtained from the one-pot reaction of alkenes with phenyliodine(III) bis(trifluoroacetate) (PIFA) in the absence of any additive or catalyst. The products were converted into the corresponding diols by ammonolysis. The use of bicyclic alkenes has shown that rearranged 1,3-diacetoxy alcohols are mostly formed as the major products. 相似文献
77.
We show that with any finite partially ordered set P (which need not be a lattice) one can associate a matrix whose determinant factors nicely. This was also noted by D.A. Smith, although his proof uses manipulations in the incidence algebra of P while ours is combinatorial, using nonintersecting paths in a digraph. As corollaries, we obtain new proofs for and generalizations of a number of results in the literature about GCD matrices and their relatives. 相似文献
78.
Dipl.-Phys. Lena Scherthan Rouven F. Pfleger Dr. Hendrik Auerbach Dipl.-Phys. Tim Hochdörffer Dr. Juliusz A. Wolny Dr. Wenli Bi Dr. Jiyong Zhao Dr. Michael Y. Hu Dr. E. Ercan Alp Dr. Christopher E. Anson Prof. Rolf Diller Prof. Annie K. Powell Prof. Volker Schünemann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8902-8907
79.
Ender Ercan Yan-Cheng Lin Chun-Kai Chen Yi-Kai Fang Wei-Chen Yang Yun-Fang Yang Wen-Chang Chen 《Journal of polymer science. Part A, Polymer chemistry》2022,60(3):525-537
Photonic field-effect transistor (FET) memory devices offer unique advantages owing to their solution processability, low cost production, and their lightweight and structural flexibility. Despite the plethora of research demonstrated the photon based programming process, limited reports are available for photoinduced recovery mechanism in such devices. To investigate the influence of polymer electret design on photonic memory performance, poly(9,9-dioctylfluorene) (PFO)–block–poly (vinylphenyl oxadiazole) (POXD) conjugated block copolymers were employed to a photonic FET memory with n-type semiconducting channel. The studied device exhibited bistable ON/OFF current states after electrical programming and photoinduced recovery (erasing) processes. The device operating mechanism was elaborated by comparing the device performance with respective electrets of PFO-b-POXD and PFO-b-polystyrene (PS) and PFO homopolymer. We found that PFO-b-POXD can efficiently generate photoexciton under UV illumination to neutralize the trapped hole, and assuage the hole trapping propensity of PFO segment, simultaneously. By optimizing the POXD content in the block copolymer, a decent memory ratio (ION/IOFF) of ~105 was achieved after 104 s, indicating its superior long-term stability and data discernibility. This research shows the judicious strategy to design polymer electret for photonic memory, and it opens up the possibility of developing photonic memory, human perception and futuristic communication systems using simple, convenient and reliable optoelectronic technique. 相似文献
80.
In this paper we give the definition of the Fluctuationlessness concept and using this concept we make approximations to univariate
functions by using Taylor expansion with the explicit remainder term. Then integrating this approximate expression we obtain
a new quadrature-like numerical integration method. The results of numerical experiments are compared with the results obtained
from the corresponding Taylor series expansion without the remainder term and errors are analyzed. 相似文献