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941.
A practical synthetic route for the preparation of 2-pyridyl and 3-pyridyl derivatives has been accomplished by utilizing a simple coupling reaction of stable 2-pyridylzinc bromides and 3-pyridylzinc bromides. The organozincs used in this study were easily prepared via the direct insertion of active zinc into the corresponding bromopyridines. The subsequent coupling reactions with a variety of different electrophiles have afforded the corresponding coupling products. Using highly active manganese, a variety of Grignard-type organomanganese reagents have been obtained. The subsequent coupling reactions of the resulting organomanganese reagents with several electrophiles have also been accomplished under mild conditions. 相似文献
942.
The objective of this study was to evaluate the performance of a photocatalysis/H2O2/metal membrane hybrid system in the degradation of humic acid. A metal membrane of nominal pore size 0.5 μm was used in the
experiment for separation of TiO2 particles. Hydrogen peroxide was tested as an oxidant. The efficiency of removal of CODCr and color increased rapidly for initial hydrogen peroxide concentrations up to 50 mg L−1. The efficiency of removal of CODCr and color by 50 mg L−1 initial hydrogen peroxide concentration was approximately 95 and 98%, respectively. However, addition of hydrogen peroxide
over 50 mg L−1 inhibited the efficiency of the system. Addition of hydrogen peroxide to a UV/TiO2 system enhanced efficiency of removal of CODCr and color compared with no addition of hydrogen peroxide. This may be ascribed to capture electrons ejected from TiO2 and to the production of OH radicals. Application of the metal membrane in the UV/TiO2/H2O2 system enhanced the efficiency of removal of CODCr and color because of adsorption by the metal membrane surface and the production of OH radicals. By application of a metal
membrane with a nominal pore size of 0.5 μm, TiO2 particles were effectively separated from the treated water by metal membrane rejection. The photocatalytic metal membrane
had much less resistance than the humic acid, TiO2, and humic acid/TiO2 because of the degradation of humic acid by the photocatalytic reaction. 相似文献
943.
Sang-Bok Ma Kyung-Wan Nam Won-Sub Yoon Seong-Min Bak Xiao-Qing Yang Byung-Won Cho Kwang-Bum Kim 《Electrochemistry communications》2009,11(8):1575-1578
Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 °C for 30 min using MnO2-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite. 相似文献
944.
Hasell T Chong SY Jelfs KE Adams DJ Cooper AI 《Journal of the American Chemical Society》2012,134(1):588-598
We present here a simple method for the bottom-up fabrication of microporous organic particles with surface areas in the range 500-1000 m(2) g(-1). The method involves chiral recognition between prefabricated, intrinsically porous organic cage molecules that precipitate spontaneously upon mixing in solution. Fine control over particle size from 50 nm to 1 μm can be achieved by varying the mixing temperature or the rate of mixing. No surfactants or templates are required, and the resulting organic dispersions are stable for months. In this method, the covalent synthesis of the cage modules can be separated from their solution processing into particles because the modules can be dissolved in common solvents. This allows a "mix and match" approach to porous organic particles. The marked solubility change that occurs upon mixing cages with opposite chirality is rationalized by density functional theory calculations that suggest favorable intermolecular interactions for heterochiral cage pairings. The important contribution of molecular disorder to porosity and surface area is highlighted. In one case, a purposefully amorphized sample has more than twice the surface area of its crystalline analogue. 相似文献
945.
Jung CY Kim JS Kim HS Ha JM Kim ST Lim HJ Koo SM 《Journal of colloid and interface science》2012,367(1):257-263
Monodispersed, submicron-sized Janus ORMOSIL particles with multiple functional groups were prepared by the selective surface reaction of a monolayer film formed at a hexane-water interface. A well-ordered monolayer film was obtained by self-assembly of ORMOSIL particles with multiple functional groups at hexane-water interface. The photopolymerization of an ordered monolayer containing ORMOSIL particles yields a rigid film strong enough to maintain its integrity for transfer and further chemical reaction. The chemical reaction of this ordered film with organic and inorganic functional groups produced Janus ORMOSIL particles with multiple functional groups. The morphologies, structures, and chemical compositions of monolayer films and Janus ORMOSIL particles were characterized by FT-IR, solid state NMR, X-ray diffraction (XRD), optical microscopy (OM), electron microscopies (SEM and TEM), and confocal laser scanning microscopy. 相似文献
946.
Park IW Yoo J Kim B Adhikari S Kim SK Yeon Y Haynes CJ Sutton JL Tong CC Lynch VM Sessler JL Gale PA Lee CH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(9):2514-2523
A ditopic ion-pair receptor (1), which has tunable cation- and anion-binding sites, has been synthesized and characterized. Spectroscopic analyses provide support for the conclusion that receptor 1 binds fluoride and chloride anions strongly and forms stable 1:1 complexes ([1·F](-) and [1·Cl](-)) with appropriately chosen salts of these anions in acetonitrile. When the anion complexes of 1 were treated with alkali metal ions (Li(+), Na(+), K(+), Cs(+), as their perchlorate salts), ion-dependent interactions were observed that were found to depend on both the choice of added cation and the initially complexed anion. In the case of [1·F](-), no appreciable interaction with the K(+) ion was seen. On the other hand, when this complex was treated with Li(+) or Na(+) ions, decomplexation of the bound fluoride anion was observed. In contrast to what was seen with Li(+), Na(+), K(+), treating [1·F](-) with Cs(+) ions gave rise to a stable, host-separated ion-pair complex, [F·1·Cs], which contains the Cs(+) ion bound in the cup-like portion of the calix[4]pyrrole. Different complexation behavior was seen in the case of the chloride complex, [1·Cl](-). Here, no appreciable interaction was observed with Na(+) or K(+). In contrast, treating with Li(+) produces a tight ion-pair complex, [1·Li·Cl], in which the cation is bound to the crown moiety. In analogy to what was seen for [1·F](-), treatment of [1·Cl](-) with Cs(+) ions gives rise to a host-separated ion-pair complex, [Cl·1·Cs], in which the cation is bound to the cup of the calix[4]pyrrole. As inferred from liposomal model membrane transport studies, system 1 can act as an effective carrier for several chloride anion salts of Group 1 cations, operating through both symport (chloride+cation co-transport) and antiport (nitrate-for-chloride exchange) mechanisms. This transport behavior stands in contrast to what is seen for simple octamethylcalix[4]pyrrole, which acts as an effective carrier for cesium chloride but does not operates through a nitrate-for-chloride anion exchange mechanism. 相似文献
947.
Cho KB Kim EJ Seo MS Shaik S Nam W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(33):10444-10453
The experimentally measured bimolecular reaction rate constant, k(2) , should in principle correlate with the theoretically calculated rate-limiting free energy barrier, ΔG(≠) , through the Eyring equation, but it fails quite often to do so due to the inability of current computational methods to account in a precise manner for all the factors contributing to ΔG(≠) . This is further aggravated by the exponential sensitivity of the Eyring equation to these factors. We have taken herein a pragmatic approach for C?H activation reactions of 1,4-cyclohexadiene with a variety of octahedral nonheme Fe(IV) O complexes. The approach consists of empirically determining two constants that would aid in predicting experimental k(2) values uniformly from theoretically calculated electronic energy (ΔE(≠) ) values. Shown in this study is the predictive power as well as insights into energy relationships in Fe(IV) O C?H activation reactions. We also find that the difference between ΔG(≠) and ΔE(≠) converges at slow reactions, in a manner suggestive of changes in the importance of the triplet spin state weight in the overall reaction. 相似文献
948.
949.
A new pentacoordinated ferrous compound [TPAFeCl]+ (TPA = tris(2-pyridylmethyl)amine) was synthesized from the reaction between H3TPA(ClO4)3 and Fe(PnPr3)2Cl2 in MeCN. The unique trigonal bipyramidal [TPAFeCl]+ complex was characterized as a S = 2 high spin complex based on the crystallographic structure, magnetic susceptibility, 1H NMR spectrum and semi-empirical ZINDO/S calculations. Crystal of [TPAFeCl]2(FeCl4)(MeCN)2 was monoclinic with a = 12.019(2) Å, b = 27.550(5) Å, c = 14.138(2) Å, β = 94.168(3)°, V = 4668.9(13) Å3, space group C/c, and the unit cell contained a racemic mixture of Δ and Λ isomers with ferrous tetrachloride anion. 相似文献
950.
Peterka DS Kim JH Wang CC Poisson L Neumark DM 《The journal of physical chemistry. A》2007,111(31):7449-7459
The photoionization and photoelectron spectroscopy of pure He droplets were investigated at photon energies between 24.6 eV (the ionization energy of He) and 28.0 eV. Time-of-flight mass spectra and photoelectron images were obtained at a series of molecular beam source temperatures and pressures to assess the effect of droplet size on the photoionization dynamics. At source temperatures below 16 K, where there is significant production of clusters with more than 10(4) atoms, the photoelectron images are dominated by fast electrons produced via direct ionization, with a small contribution from very slow electrons with kinetic energies below 1 meV arising from an indirect mechanism. The fast photoelectrons from the droplets have as much as 0.5 eV more kinetic energy than those from atomic He at the same photon energy. This result is interpreted and simulated within the context of a "dimer model", in which one assumes vertical ionization from two nearest-neighbor He atoms to the attractive region of the He2+ potential energy curve. Possible mechanisms for the slow electrons, which were also seen at energies below IE(He), are discussed, including vibrational autoionizaton of Rydberg states comprising an electron weakly bound to the surface of a large HeN+ core. 相似文献