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1.
Heng Yi Pengfei Hu Prof. Dr. Scott A. Snyder 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(7):2696-2700
Pd-catalyzed sequences involving oxidative addition, cyclization, and termination through intermolecular nucleophile capture have tremendous utility. Indeed, they can generate a plethora of different polycyclic structures possessing a diverse range of functionality. However, one area of deficiency for Pd0/PdII variants is the ability to conclude them with oxygen-based species. Inspired by the recent discovery of one such reaction in the course of a total synthesis program, we delineate herein that it has significant strength, both in terms of substrate scope as well as the terminating oxygen nucleophile. As a result, the reaction proved critical in achieving total syntheses of two oxygenated natural products, one of which was prone to over-oxidation. Finally, a mechanistic proposal that accounts for its success is provided. 相似文献
2.
Ying Zhang Weidong Cui Aaron T. Wecksler Hao Zhang Patricia Molina Galahad Deperalta Michael L. Gross 《Journal of the American Society for Mass Spectrometry》2016,27(7):1139-1142
Native mass spectrometry (MS) and top-down electron-capture dissociation (ECD) combine as a powerful approach for characterizing large proteins and protein assemblies. Here, we report their use to study an antibody Fab (Fab-1)–VEGF complex in its near-native state. Native ESI with analysis by FTICR mass spectrometry confirms that VEGF is a dimer in solution and that its complex with Fab-1 has a binding stoichiometry of 2:2. Applying combinations of collisionally activated dissociation (CAD), ECD, and infrared multiphoton dissociation (IRMPD) allows identification of flexible regions of the complex, potentially serving as a guide for crystallization and X-ray diffraction analysis. 相似文献
3.
The directing mechanisms of liquid directing agents of zeolite Y and zeolite L were studied by means of light transmission, ultracentrifugation, NMR, XRD and “cross-exchange” experiments. It was discovered that not only microcfystals of zeolites, but also cage structures of zeolites play the directing role for crystallization of zeolites. 相似文献
4.
The possibility of crystallizing silicalite-1 (MFI) from the pore walls of as-synthesized MCM-41 via steam-assisted crystallization (SAC) was thoroughly investigated. A kinetic study was conducted through the impregnation of as-synthesized MCM-41 with the structure-directing agent tetrapropyl-ammonium hydroxide (TPAOH). Materials obtained after different SAC treatment times (1–288 h) were characterized by XRD, nitrogen physisorption at 77 K, TGA/DTA, and SEM. The achieved results allowed us to conclude that during SAC treatment, rapid destruction of the hexagonal mesophase occurs with the enlargement of mesopores, probably by their coalescence, until achieving non-porous amorphous silica. Only thereafter is the crystallization of the MFI phase evidenced through the development of micron-sized (>10 µm) MFI structured crystals. This study suggests the probable practical impossibility of even partial crystallization of the pore walls of mesoporous materials by SAC. 相似文献
5.
Triammonium-N-dithiocarboxyiminodiacetate,
(NH4)3L, a new dithiocarbamato
derivative of iminodiacetate, has been synthesized. The coordination properties
of the ligand were tested in reactions with copper(II), nickel(II) and palladium(II)
salts in acidic solutions. Complexes with a general formula M(H2L)2
were obtained, with the coordination taking place through the sulfur atoms
of the dithiocarbamate moiety. The new compounds were characterized by elemental
analysis, UV/VIS and IR spectroscopy, thermal analysis and magnetic measurements.
In addition, the ligand was characterized by 1H-
and 13C-NMR spectroscopy and molar conductivity
measurements. The copper(II) complex is paramagnetic, while the nickel(II)
and palladium(II) compounds are diamagnetic. The thermal decomposition of
all compounds is continuous and the thermal stability of the complexes is
higher than that of the ligand, as expected. 相似文献
6.
Musa Gogebakan Ibrahim Karteri Baris Avar Celal Kursun 《Journal of Thermal Analysis and Calorimetry》2012,110(2):793-798
Amorphous Mg61Cu24Y15 ribbons were manufactured by melt-spinning at wheel speeds in the range 5?C20?ms?1. The crystallization behavior of amorphous ribbons was investigated by a combination of differential scanning calorimetry (DSC) and X-ray diffractometry. DSC measurements showed that the amorphous ribbons exhibit distinct glass transition temperature and wide supercooled liquid region before crystallization. During continuous heating three exothermic peaks and two endothermic peaks were observed. The characteristic thermodynamic parameters such as T g, T x , ??T x , and T rg are around 432?C439, 478?C485, 46?C54?K, and 0.55?C0.56, respectively. Isothermal annealing DSC traces for this amorphous alloy, the first crystallization peak showed a clear incubation period and Avrami exponent was found to be 2.30?C2.74, which indicate that the transformation reaction involved nucleation and three-dimensional diffusion controlled growth. Mechanical properties of the as-quenched and subsequently annealed ribbons were examined by Vickers microhardness (HV) measurements. Results showed that microhardness of the as-quenched ribbons were about 309?HV. However, the results also showed that microhardness of the rapidly solidified ribbons increases with the increasing temperature. 相似文献
7.
《结构化学》2017,(4)
A new coordination polymer, namely [ZnBr(bmb)(Hbmb)]_n(1)(Hbmb = 3-benzoimidazol-1-yl-benzoic acid), has been synthesized through a hydrothermal method and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectra, thermogravimetric analysis, and fluorescent characterization. The crystal structure is of triclinic system, space group P1 with a = 10.637(3), b = 11.660(3), c = 12.406(3) ?, α = 103.462(3), β = 105.144(3), γ = 110.513(3)o, V = 1298.5 ?~3, C_(28)H_(19)N_4O_4 ZnBr, Mr = 624.0, Z = 2, Dc = 1.588 g/cm~3, F(000) = 624, the final R = 0.0253 and w R = 0.0616 for 4385 observed reflections. The polymer features a chain-like structure and stabilizes itself by interchain hydrogen bonds to form a 2D supramolecular structure. 1 exhibits a strong blue emission with a fluorescent lifetime of 1.13 ns, and emitting mechanism of ligand-centered charge transition also was confirmed by the first-principle calculation. 相似文献
8.
Anup Kumar P. B. Barman Raman Sharma 《Journal of Thermal Analysis and Calorimetry》2013,114(3):1003-1013
Effect of Ag doping on the crystallization kinetics of amorphous Se80.5Bi1.5Te18?yAgy (for y = 0, 1.0, 1.5, and 2.0 at.%) glassy alloys has been studied by differential scanning calorimetry (DSC). The DSC curves recorded at four different heating rates are analyzed to determine the transition temperature, activation energy, thermal stability, glass forming ability, and dimensionality of growth during phase transformation. Present study shows that the thermal stability and the glass-forming ability increase with an increase in the Ag content which is in agreement with the earlier studies. Our results show that Se80.5Bi1.5Te16Ag2 composition is thermally more stable and has a little tendency to crystallize in comparison to other compositions under study. The increase in thermal stability with increasing Ag concentration is attributed to an increase in the cohesive energy. 相似文献
9.
Hua Ke Wen Wang Lin Chen Jiahuan Xu Dechang Jia Zhe Lu Yu Zhou 《Journal of Sol-Gel Science and Technology》2010,53(1):135-140
We present a facile sol–gel route to synthesize lanthanum-substituted bismuth titanate (BLT). The chemical reactions and crystallization
process of this method using the initial materials of bismuth subnitrate [4BiNO3(OH)2·BiO(OH)], lanthanum nitrate [La(NO3)3·6H2O] and tetrabutyl titanate [Ti(C4H9O)4] were investigated by thermogravimetric and differential thermal analysis, IR spectroscopy, gas chromatography/mass spectrometry,
Raman spectroscopy and XRD. The evaporation of the dissolved CO2 in the amorphous BLT matrix is associated with the crystallization of BLT. The BLT gel is pure BLT perovskite when calcination
temperature is higher than 500 °C. The grain size of the obtained nanoparticles ranges from 15 to 82 nm. The Arrhenius curve
is obtained from the representation of the reduced sizes with respect to the calcination temperature. The activation energy
of grain growth in BLT nanoparticles is 0.36 eV, which shows a rapidly growth process in the temperature range of 500–850 °C. 相似文献
10.
Pawan Heera Anup Kumar Raman Sharma 《Journal of Thermal Analysis and Calorimetry》2017,128(2):661-673
The objective of this study was to explore an innovative type of form-stable phase-change materials (PCMs) with flexible cellulose acetate (CA) nano-fibrous felts (nano-felts) absorbed with capric–myristic–stearic acid ternary eutectic mixture for thermal energy storage/retrieval. Capric–myristic–stearic acid (CMS) ternary eutectic mixture as model PCM was firstly prepared. The developed CA nano-felts as supporting material was mechanically flexible and was made from CA/polyvinylpyrrolidone (PVP) precursor composite nanofibers followed by removal of PVP components. The effects of original mass ratio of CA/PVP on absorption capacities of CA nano-felts were studied. The modified CA nano-felts with groove/porous structure and rough surfaces were capable of absorbing a large amount of PCMs. The morphological structures, as well as the properties of thermal energy storage, thermal stability and reliability, and thermal insulation of composite PCMs were characterized by scanning electron microscopy, differential scanning calorimetry, and thermal performance measurement, respectively. The results showed that CMS eutectic was absorbed in and/or supported by modified CA nano-felts. The heat enthalpy values of composite PCMs have slightly decreased in comparison with the corresponding theoretical values. The composite PCMs demonstrated good thermal stability and reliability after thermal cycles. The composite PCMs had high thermal insulation capability for temperature regulation. 相似文献
11.
WeiRongYAN YaoTingYU NanDONG 《中国化学快报》2003,14(7):693-696
Myasthenia Gravis (MG) is an organ specific autoimmune disease mediated by autoantibodies (AChR Ab) against the acetylcholine receptor (AChR). Literature reported that the AChR Ab can be removed by absorbent linked with tryotophan.It was studied in detail in our lab. With the aid of computer, we docked some ligandsinto AChR Ab, and the results fromscores of docking under different generations showed that therewas no specific binding between tryptophan and scFv fragment just as the binding between antigen-antibody. The interaction between Trp and immunoglobulin was a broad-spectntm binding. 相似文献
12.
Russian Chemical Bulletin - The molar vaporization enthalpies and vapor—liquid phase equilibria of a benzene—cyclohexane system were calculated for the full concentration range at... 相似文献
13.
Migas Damian Gradoń Paweł Mikuszewski Tomasz Moskal Grzegorz 《Journal of Thermal Analysis and Calorimetry》2020,142(5):1739-1747
Journal of Thermal Analysis and Calorimetry - In the investigation, crystallization behavior of ternary γ–γ′ alloy based on Co–Al–W system was analyzed. The alloy... 相似文献
14.
15.
Balbir Singh Patial Nagesh Thakur S. K. Tripathi 《Journal of Thermal Analysis and Calorimetry》2011,106(3):845-852
Calorimetric study of Se85−x
Te15Sn
x
(x = 0, 2, 4 and 6) glassy alloys have been performed using Differential Scanning Calorimetry (DSC) under non-isothermal conditions
at four different heating rates (5, 10, 15 and 20 °C/min). The glass transition temperature and peak crystallization temperature
are found to increase with increasing heating rate. It is remarkable to note that a second glass transition region is associated
with second crystallization peak for Sn additive Se–Te investigated samples. Three approaches have been employed to study
the glass transition region. The kinetic analysis for the first crystallization peak has been taken by three different methods.
The glass transition activation energy, the activation energy of crystallization, and Avrami exponent (n) are found to be composition dependent. The crystallization ability is found to increase with increasing Sn content. From
the experimental data, the temperature difference (T
p − T
g) is found to be maximum for Se83Te15Sn2 alloy, which indicates that this alloy is thermally more stable in the composition range under investigation. 相似文献
16.
Petr Svoboda Dagmar Svobodova Petr Slobodian Toshiaki Ougizawa Takashi Inoue 《Polymer Testing》2009,28(2):215-222
Blends of polypropylene and ethylene–octene copolymers (EOC) were investigated by transmission electron microscopy, optical microscopy and differential scanning calorimetry (DSC). The main focus was on phase morphology and crystallization for blends containing EOC with different octene content (28, 37 and 52 wt.%). Also, for a given octene content (37 wt.%), the effect of molecular weight (115, 180, 229k) of EOC on morphology was observed. The largest particles were found in the blend with EOC-28 and the smallest with EOC-52. This blend with the smallest particles exhibits the fastest crystallization kinetics by two independent methods, optical microscopy and DSC. This behavior was explained by a model. Crystallizing polypropylene lamellae have to travel a longer distance going around large particles, which slows down overall crystallization growth rate. In the case of smaller particles, the obstacles are smaller and the crystallization is faster. 相似文献
17.
S. J. Pfleiderer D. Lützenkirchen-Hecht R. Frahm 《Journal of Sol-Gel Science and Technology》2012,64(1):27-35
Nano-composite TiO2?CZrO2 materials were prepared via sol?Cgel processes by hydrolysis of mixtures of titanium- and zirconium-containing alkoxides with TiO2:ZrO2 ratios of 1:2, 1:1, 2:1, and 10:1. Precipitated powders were dried at room temperature and annealed in ambient air at temperatures between 350 and 500?°C for 4?h. Pure TiO2 and ZrO2 powders were synthesized for comparison. Samples were characterized with X-ray diffraction (XRD) and X-ray absorption near edge fine structure (XANES). The detailed analysis of those data provides the crystalline and amorphous phase composition as well as the crystallite particle size. According to XRD and XANES analysis, only the two pure oxide samples and one of the composite samples with a composition TiO2:ZrO2?=?10:1, crystallized. Both titania containing powders, the pure TiO2 and the TiO2:ZrO2?=?10:1 composite, were found to crystallize in the anatase structure. ZrO2 was found to stay amorphous in the composites but crystalline in the pure oxide. In the crystallized composite TiO2:ZrO2?=?10:1 sample, the concentration of the amorphous phase remains larger than in pure TiO2 samples, but the crystallite size was found to be nearly constant with increasing annealing temperature in contrast to the increasing particle size of pure TiO2-samples. Pure TiO2 precipitates are amorphous directly after preparation, however they crystallize after 6?month storage at ambient conditions by aging. Such an aging was not observed for the TiO2:ZrO2 composites. 相似文献
18.
19.
The finite difference method is employed to solve three-dimensional equations of nonstationary convective diffusion for blank-ion concentrations. To correctly calculate the current density at the edge of a round electrode, the coordinate system of an oblate ellipsoid is applied. Kinetic boundary conditions valid for a redox reaction form at the surface of the sensor electrode. 相似文献
20.
Chirkov Yu. G. Rostokin V. I. Andreev V. N. Bogdanovskaya V. A. 《Russian Journal of Electrochemistry》2020,56(3):230-238
Russian Journal of Electrochemistry - Currently, the development of lithium–oxygen (air) battery became a hot topic. It is recognised that its specific energy will exceed that of traditional... 相似文献