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81.
Ovender Singh Priyanka Gupta Anshu Singh Ankur Maji Udai P. Singh Kaushik Ghosh 《应用有机金属化学》2019,33(5)
Hexacoordinated non‐heme iron complexes [FeII(L1)2](ClO4)2 ( 1 ) and [FeII(L2)2](PF6)2 ( 2 ) have been synthesized using ligands L1 = (E)‐2‐chloro‐6‐(2‐(pyridin‐2ylmethylene) hydrazinyl)pyridine and L2 = (E)‐2‐chloro‐6‐(2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinyl) pyridine]. These complexes are highly active non‐heme iron catalysts to catalyze the C (sp3)?H bonds of alkanes. These iron complexes have been characterized using ESI?MS analysis and molecular structures were determined by X‐ray crystallography. ESI ? MS analysis also helped to understand the generation of intermediate species like FeIII?OOH and FeIV=O. DFT and TD?DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes. 相似文献
82.
Friedrich Kreyenschmidt Selim E. Meurer Prof. Dr. Konrad Koszinowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(23):5912-5921
>The combination of CoCl2 with bidentate phosphines is known to catalyze challenging cross-coupling and Heck-type reactions, but the mechanisms of these valuable transformations have not been established. Here, we use electrospray-ionization mass spectrometry to intercept the species formed in these reactions. Our results indicate that a sequence of transmetalation, reductive elimination, and redox disproportionation convert the cobalt(II) precatalyst into low-valent cobalt complexes. These species readily transfer single electrons to alkyl bromides, which thereupon dissociate into alkyl radicals and Br−. In cross-coupling reactions, the alkyl radicals add to the cobalt catalyst to form observable heteroleptic complexes, which release the coupling products through reductive eliminations. In the Heck-type reactions, the low abundance of newly formed ionic species renders the analysis more difficult. Nonetheless, our results also point to the occurrence of single-electron transfer processes and the involvement of radicals in these transformations. 相似文献
83.
Alexander G. Shard Rasmus Havelund Martin P. Seah Charles A. Clifford 《Surface and interface analysis : SIA》2019,51(10):1018-1020
The International Standard ISO 22415 provides methods to measure sputtering yield volumes of organic test materials using argon cluster ions. The test materials should consist of thin films of known thicknesses between 50 and 1000 nm. The format of the test materials, the measurement of sputtering ion dose, sputtered depth, and reporting requirements for sputtering yield volumes are described. 相似文献
84.
Abstract For KNb1-xTaxO3 crystals the influence of the Ta-concentration on the phase-matching properties for optical second harmonic generation (SHG) was measured. For non-critical phase matched SHG of the Nd:YAG-laser (1064nm) the coefficient d31 of the tensor of the nonlinear susceptibility was applied, while for the GaAs-laser (905 nm) the coefficient d32 was used. For both laser wavelengths the phase-matching temperature decreases with increasing Ta-concentration. Non-critical phase-matching at room temperature can be reached with the GaAs-laser for a Ta-concentration of ≈9%. The corresponding value for the Nd:YAG-laser is ≈14%. 相似文献
85.
《Angewandte Chemie (International ed. in English)》2017,56(47):14808-14835
Flash vacuum pyrolysis (FVP) had its beginnings in the 1940s and 1950s, mainly through mass spectrometric detection of pyrolytically formed free radicals. In the 1960s many organic chemists started performing FVP experiments with the purpose of isolating new and interesting compounds and understanding pyrolysis processes. Meanwhile, many different types of apparatus and techniques have been developed, and it is the purpose of this review to present the most important methods as well as a survey of typical reactions and observations that can be achieved with the various techniques. This includes preparative FVP, chemical trapping reactions, matrix isolation, and low temperature spectroscopy of reactive intermediates and unstable molecules, the use of online mass, photoelectron, microwave, and millimeterwave spectroscopies, gas‐phase laser pyrolysis, pulsed pyrolysis with supersonic jet expansion, very low pressure pyrolysis for kinetic investigations, solution‐spray and falling‐solid FVP for involatile compounds, and pyrolysis over solid supports and reagents. Moreover, the combination of FVP with matrix isolation and photochemistry is a powerful tool for investigations of reaction mechanism. 相似文献
86.
ABSTRACT In this paper, we present a systematic roadmap for developing a robust and parallel multi-material reactive hydrodynamic solver that integrates historically stable algorithms with new and current modern methods to solve explosive system design problems. The Ghost Fluid Method and Riemann solvers were used to enforce appropriate interface boundary conditions. Improved performance in terms of computational work and convergence properties was achieved by modifying a local node sorting strategy that decouples ghost nodes, allowing us to set material boundary conditions via an explicit procedure, removing the need to solve a coupled system of equations numerically. The locality and explicit nature of the node sorting concept allows for greater levels of parallelism and lower computational cost when populating ghost nodes. Non-linear numerical issues endemic to the use of real Equations of State in hydro-codes were resolved by using more thermodynamically consistent forms allowing us to accurately resolve large density gradients associated with high energy detonation problems at material interfaces. Pre-computed volume tables were implemented adding to the robustness of the solver base. 相似文献
87.
Yukun Li Leela Christian‐Tabak Vivien Li Fong Fuan Jiong Zou Chong Cheng 《Journal of polymer science. Part A, Polymer chemistry》2014,52(22):3250-3259
Amphiphilic double‐brush copolymers (DBCs) with each graft site quantitatively carrying both a hydrophilic poly(ethylene oxide) (PEO) graft and a hydrophobic polystyrene (PSt) graft are synthesized by sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization and ring‐opening metathesis polymerization (ROMP). These DBCs are used as both surfactants and polyfunctional RAFT agents in the radical polymerization of St in aqueous dispersed media. Miniemulsions with narrowly dispersed St‐based nanodroplets are readily obtained after ultrasonication of the reaction mixtures. Without the presence of crosslinker, chain‐extension polymerization of St from the DBCs yields well‐defined polymeric latexes with narrow size distributions. However, with the presence of divinylbenzene (DVB) as the crosslinker, vesicular polymeric nanoparticles are formed as the major product. Such crosslinking‐induced change in morphology of the resulting latex nanomaterials may be ascribed to the increase of interfacial curvature in the heterophase systems during crosslinking polymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3250–3259 相似文献
88.
Ryota Seto Kozo Matsumoto Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2014,52(13):1832-1842
Reactivity of isothiocynate moieties in the side chain of polymethacrylate with amine, alcohol, or thiol was investigated, and the reactions were applied to preparation of networked polymers. Isothiocyanate of polymer side chain rapidly reacted with amines without a catalyst, to give the corresponding thioureas. However, it did not react with alcohols or thiols under the same conditions. Using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as a catalyst, addition of alcohols or thiols to the isothiocyanate proceeded smoothly. Addition of amines, alcohols, and thiols to isothiocyanates moiety contained in the side chain of polymethacrylate also proceeded readily with or without the catalyst, respectively, to effectively give the corresponding side chain modified polymers. Occurrence of these additions was confirmed by 1H NMR and IR measurements. Glass transition temperatures and thermal decomposition temperatures of the obtained polymers were investigated by differential scanning calorimetry and thermogravimetric analysis. Networked polymers were easily prepared by addition of 1,6‐hexamethylenediamine or hexamethylene glycol to the polymethacrylate having isothiocyanato groups. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1832–1842 相似文献
89.
Pierre Garcia Dr. Yannick Evanno Dr. Pascal George Dr. Mireille Sevrin Dr. Gino Ricci Prof. Dr. Max Malacria Dr. Corinne Aubert Prof. Dr. Vincent Gandon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4337-4344
An in‐depth study of the cobalt‐catalyzed [2+2+2] cycloaddition between yne‐ynamides and nitriles to afford aminopyridines has been carried out. About 30 nitriles exhibiting a broad range of steric demand and electronic properties have been evaluated, some of which open new perspectives in metal‐catalyzed arene formation. In particular, the use of [CpCo(CO)(dmfu)] (dmfu=dimethyl fumarate) as a precatalyst made possible the incorporation of electron‐deficient nitriles into the pyridine core. Modification of the substitution pattern at the yne‐ynamide allows the regioselectivity to be switched toward 3‐ or 4‐aminopyridines. Application of this synthetic methodology to the construction of the aminopyridone framework using a yne‐ynamide and an isocyanate was also briefly examined. DFT computations suggest that 3‐aminopyridines are formed by formal [4+2] cycloaddition between the nitrile and the intermediate cobaltacyclopentadiene, whereas 4‐aminopyridines arise from an insertion pathway. 相似文献
90.
Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl 下载免费PDF全文
Christoph Schnegelsberg Sebastian Bachmann Marlene Kolter Thomas Auth Dr. Michael John Prof. Dr. Dietmar Stalke Prof. Dr. Konrad Koszinowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(23):7752-7762
Grignard reagents RMgCl and their so‐called turbo variant, the highly reactive RMgCl?LiCl, are of exceptional synthetic utility. Nevertheless, it is still not fully understood which species these compounds form in solution and, in particular, in which way LiCl exerts its reactivity‐enhancing effect. A combination of electrospray‐ionization mass spectrometry, electrical conductivity measurements, NMR spectroscopy (including diffusion‐ordered spectroscopy), and quantum chemical calculations is used to analyze solutions of RMgCl (R=Me, Et, Bu, Hex, Oct, Dec, iPr, tBu, Ph) in tetrahydrofuran and other ethereal solvents in the absence and presence of stoichiometric amounts of LiCl. In tetrahydrofuran, RMgCl forms mononuclear species, which are converted into trinuclear anions as a result of the concentration increase experienced during the electrospray process. These trinuclear anions are theoretically predicted to adopt open cubic geometries, which remarkably resemble structural motifs previously found in the solid state. The molecular constituents of RMgCl and RMgCl?LiCl are interrelated via Schlenk equilibria and fast intermolecular exchange processes. A small portion of the Grignard reagent also forms anionic ate complexes in solution. The abundance of these more electron‐rich and hence supposedly more nucleophilic ate complexes strongly increases upon the addition of LiCl, thus rationalizing its beneficial effect on the reactivity of Grignard reagents. 相似文献