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121.
Francis X. Smith Brian D. Williams Eric Gelsleichter Judy A. Podcasy John T. Sisko David M. Hrubowchak 《合成通讯》2013,43(6):765-769
It was found that 3‐acyl derivatives of oxindoles, benzo[b]furan‐2‐ones, and benzo[b]thiophen‐2‐ones could be efficiently and conveniently reduced to the corresponding alkyl derivatives by pelletized sodium borohydride in acetic acid. A typical procedure involves heating the acylated substrates for approximately 90 min in a slurry of glacial acetic acid and sodium borohydride to provide the 3‐alkyl product in yields ranging from 62% to 96%. This synthetic methodology represents a convenient approach to the synthesis of the alkyl derivatives. 相似文献
122.
利用溶剂热法合成了不同锂含量的MOF-5(xLi-MOF-5, x=0, 1, 3, 5).在MOF-5结晶过程中,锂离子被合并入其骨架结构中.实验表明,合并入骨架的锂能够改变MOF-5的结构和表面化学性质.不同的xLi-MOF-5能够不同程度降低骨架相互穿插的程度从而导致其吸附分离能力的大幅改变.其中,3Li-MOF-5具有最高的二氧化碳捕获能力(5.47 mmol·g-1),对40% CO2/60% CH4混合气体具有最优吸附选择性. 相似文献
123.
Francis J. Chung 《Journal of Fourier Analysis and Applications》2015,21(3):628-665
We show that measurements of a Neumann-to-Dirichlet map, with either inputs or outputs restricted to part of the boundary, can determine an electric potential on that domain. Given a convexity condition on the domain, either the set on which measurements are taken, or the set on which input functions are supported, can be made to be arbitrarily small. The result is analogous to the result by Kenig, Sjöstrand, and Uhlmann for the Dirichlet-to-Neumann map. The main new ingredient in the proof is an improved Carleman estimate for the Schrödinger operator with appropriate boundary conditions. This is proved by Fourier analysis of a conjugated operator along the boundary of the domain. 相似文献
124.
Camille Flament Joël Ribis Jérôme Garnier Thierry Vandenberghe Jean Henry Alexis Deschamps 《哲学杂志》2015,95(8):906-917
The age hardening 6061-T6 aluminium alloy has been chosen as structural material for the core vessel of the material testing Jules Horowitz nuclear reactor. The alloy contains incoherent Al(Cr, Fe, Mn)Si dispersoids whose characterization by energy-filtered transmission electron microscopy (EFTEM) analysis shows a core/shell organization tendency where the core is (Mn, Fe) rich, and the shell is Cr rich. The present work studies the stability of this organization under irradiation. TEM characterization on the same particles, before and after 1 MeV electron irradiation, reveals that the core/shell organization is enhanced after irradiation. It is proposed that the high level of point defects, created by irradiation, ensures a radiation-enhanced diffusion process favourable to the unmixing forces between (Fe, Mn) and Cr. Shell formation may result in the low-energy interface segregation of Cr atoms within the (Fe, Mn) system combined with the unmixing of Cr, Fe and Mn components. 相似文献
125.
Israël-Martyr Mbomekallé Bassem S. Bassil Andreas Suchopar Bineta Keita Louis Nadjo Malika Ammam Mohamed Haouas Francis Taulelle Ulrich Kortz 《Journal of Cluster Science》2014,25(1):277-285
We report on an improved synthesis and structural characterization of the cyclic 48-tungsto–8-arsenate(V) [H4As8W48O184]36? (1). The mixed lithium–potassium salt of this polyanion, K26.5Li9.5[H4As8W48O184]·90H2O (KLi-1), has been studied in the solid state by IR, single-crystal X-ray diffraction, and elemental analysis, and in solution by 183W NMR spectroscopy. 相似文献
126.
Mild Bioconjugation Through the Oxidative Coupling of ortho‐Aminophenols and Anilines with Ferricyanide 下载免费PDF全文
Allie C. Obermeyer John B. Jarman Chawita Netirojjanakul Kareem El Muslemany Prof. Dr. Matthew B. Francis 《Angewandte Chemie (International ed. in English)》2014,53(4):1057-1061
Using a small‐molecule‐based screen, ferricyanide was identified as a mild and efficient oxidant for the coupling of anilines and o‐aminophenols on protein substrates. This reaction is compatible with thiols and 1,2‐diols, allowing its use in the creation of complex bioconjugates for use in biotechnology and materials applications. 相似文献
127.
Ortal Haik Francis Susai Amalraj Daniel Hirshberg Luba Burlaka Michael Talianker Boris Markovsky Ella Zinigrad Doron Aurbach Jordan K. Lampert Ji-Yong Shin Martin Schulz-Dobrick Arnd Garsuch 《Journal of Solid State Electrochemistry》2014,18(8):2333-2342
Thermodynamic instability of positive electrodes (cathodes) in Li-ion batteries in humid air and battery solutions results in capacity fading and batteries degradation, especially at elevated temperatures. In this work, we studied thermal interactions between cathode materials Li2MnO3, xLi2MnO3 .(1???x)Li(MnNiCo)O2,LiNi0.33Mn0.33Co0.33O2, LiNi0.4Mn0.4Co0.2O2, LiNi0.8Co0.15Al0.05O2 LiMn1.5Ni0.5O4, LiMn(or Fe)PO4, and battery solutions containing ethylene carbonate (EC) or propylene carbonate (PC), dimethyl carbonate (DMC) or ethylmethyl carbonate (EMC) and LiPF6 salt in the temperature range of 40–400 °C. It was found that these materials are stable chemically and well performing in LiPF6-based solutions up to 60 °C. The thermal decomposition of the electrolyte solutions starts >180 °C. The macro-structural transformations of cathode materials upon exothermic reactions were studied by transmission electron microscopy (TEM), X-ray difraction (XRD) and Raman spectroscopy. Differential scanning calorimetry (DSC) studies have shown that the exothermic reactions in the temperature range of 60–140 °C lead to partial decomposition of both the cathode material and electrolyte solution. The systems thus formed consisted of partially decomposed solutions and partially chemically delithiated cathode materials covered by reactions products. Thermal reactions terminate and this system reaches equilibrium at about 120 °C. It remains stable up to the beginning of the solution decomposition at about 180 °C. The increased content of surface Li2CO3 is found to significantly affect the thermal processes at high temperature range due to extensive exothermic decomposition at low temperatures. 相似文献
128.
Phenothiazine–BODIPY–Fullerene Triads as Photosynthetic Reaction Center Models: Substitution and Solvent Polarity Effects on Photoinduced Charge Separation and Recombination 下载免费PDF全文
Chandra B. KC Gary N. Lim Dr. Vladimir N. Nesterov Prof. Dr. Paul A. Karr Prof. Dr. Francis D'Souza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):17100-17112
Novel photosynthetic reaction center model compounds of the type donor2–donor1–acceptor, composed of phenothiazine, BF2‐chelated dipyrromethene (BODIPY), and fullerene, respectively, have been newly synthesized using multistep synthetic methods. X‐ray structures of three of the phenothiazine‐BODIPY intermediate compounds have been solved to visualize the substitution effect caused by the phenothiazine on the BODIPY macrocycle. Optical absorption and emission, computational, and differential pulse voltammetry studies were systematically performed to establish the molecular integrity of the triads. The N‐substituted phenothiazine was found to be easier to oxidize by 60 mV compared to the C‐substituted analogue. The geometry and electronic structures were obtained by B3LYP/6‐31G(dp) calculations (for H, B, N, and O) and B3LYP/6‐31G(df) calculations (for S) in vacuum, followed by a single‐point calculation in benzonitrile utilizing the polarizable continuum model (PCM). The HOMO?1, HOMO, and LUMO were, respectively, on the BODIPY, phenothiazine and fullerene entities, which agreed well with the site of electron transfer determined from electrochemical studies. The energy‐level diagram deduced from these data helped in elucidating the mechanistic details of the photochemical events. Excitation of BODIPY resulted in ultrafast electron transfer to produce PTZ–BODIPY.+–C60.?; subsequent hole shift resulted in PTZ.+–BODIPY–C60.? charge‐separated species. The return of the charge‐separated species was found to be solvent dependent. In nonpolar solvents the PTZ.+–BODIPY–C60.? species populated the 3C60* prior to returning to the ground state, while in polar solvent no such process was observed due to relative positioning of the energy levels. The 1BODIPY* generated radical ion‐pair in these triads persisted for few nanoseconds due to electron transfer/hole‐shift mechanism. 相似文献
129.
High‐Potential Perfluorinated Phthalocyanine–Fullerene Dyads for Generation of High‐Energy Charge‐Separated States: Formation and Photoinduced Electron‐Transfer Studies 下载免费PDF全文
Dr. Sushanta K. Das Andrew Mahler Prof. Angela K. Wilson Prof. Dr. Francis D'Souza 《Chemphyschem》2014,15(12):2462-2472
High oxidation potential perfluorinated zinc phthalocyanines (ZnFnPcs) are synthesised and their spectroscopic, redox, and light‐induced electron‐transfer properties investigated systematically by forming donor–acceptor dyads through metal–ligand axial coordination of fullerene (C60) derivatives. Absorption and fluorescence spectral studies reveal efficient binding of the pyridine‐ (Py) and phenylimidazole‐functionalised fullerene (C60Im) derivatives to the zinc centre of the FnPcs. The determined binding constants, K, in o‐dichlorobenzene for the 1:1 complexes are in the order of 104 to 105 M ?1; nearly an order of magnitude higher than that observed for the dyad formed from zinc phthalocyanine (ZnPc) lacking fluorine substituents. The geometry and electronic structure of the dyads are determined by using the B3LYP/6‐31G* method. The HOMO and LUMO levels are located on the Pc and C60 entities, respectively; this suggests the formation of ZnFnPc.+–C60Im.? and ZnFnPc.+–C60Py.? (n=0, 8 or 16) intra‐supramolecular charge‐separated states during electron transfer. Electrochemical studies on the ZnPc–C60 dyads enable accurate determination of their oxidation and reduction potentials and the energy of the charge‐separated states. The energy of the charge‐separated state for dyads composed of ZnFnPc is higher than that of normal ZnPc–C60 dyads and reveals their significance in harvesting higher amounts of light energy. Evidence for charge separation in the dyads is secured from femtosecond transient absorption studies in nonpolar toluene. Kinetic evaluation of the cation and anion radical ion peaks reveals ultrafast charge separation and charge recombination in dyads composed of perfluorinated phthalocyanine and fullerene; this implies their significance in solar‐energy harvesting and optoelectronic device building applications. 相似文献
130.
Raphael Bigler Kyle A. Mack Jeff Shen Paolo Tosatti Chong Han Stephan Bachmann Haiming Zhang Michelangelo Scalone Andreas Pfaltz Scott E. Denmark Stefan Hildbrand Francis Gosselin 《Angewandte Chemie (International ed. in English)》2020,59(7):2844-2849
Asymmetric hydrogenation has evolved as one of the most powerful tools to construct stereocenters. However, the asymmetric hydrogenation of unfunctionalized tetrasubstituted acyclic olefins remains the pinnacle of asymmetric synthesis and an unsolved challenge. We report herein the discovery of an iridium catalyst for the first, generally applicable, highly enantio‐ and diastereoselective hydrogenation of such olefins and the mechanistic insights of the reaction. The power of this chemistry is demonstrated by the successful hydrogenation of a wide variety of electronically and sterically diverse olefins in excellent yield and high enantio‐ and diastereoselectivity. 相似文献