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Kamil Samigullin Yashar Soltani Hans-Wolfram Lerner Matthias Wagner Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(3):189-197
Organoboranes carrying electron‐withdrawing substituents are commonly used as Lewis acidic catalysts or cocatalysts in a variety of organic processes. These Lewis acids also became popular through their application in `frustrated Lewis pairs', i.e. combinations of Lewis acids and bases that are unable to fully neutralize each other due to steric or electronic effects. We have determined the crystal and molecular structures of four heteroleptic arylboranes carrying 2‐(trifluoromethyl)phenyl, 2,6‐bis(trifluoromethyl)phenyl, 3,5‐bis(trifluoromethyl)phenyl or mesityl substituents. [3,5‐Bis(trifluoromethyl)phenyl]bis[2‐(trifluoromethyl)phenyl]borane, C22H11BF12, (I), crystallizes with two molecules in the asymmetric unit which show very similar geometric parameters. In one of the two molecules, both trifluoromethyl groups of the 3,5‐bis(trifluoromethyl)phenyl substituent are disordered over two positions. In [3,5‐bis(trifluoromethyl)phenyl]bis[2,6‐bis(trifluoromethyl)phenyl]borane, C24H9BF18, (II), only one of the two meta‐trifluoromethyl groups is disordered. In [2,6‐bis(trifluoromethyl)phenyl]bis[3,5‐bis(trifluoromethyl)phenyl]borane, C24H9BF18, (III), both meta‐trifluoromethyl groups of only one 3,5‐bis(trifluoromethyl)phenyl ring are disordered. [3,5‐Bis(trifluoromethyl)phenyl]dimesitylborane, C26H25BF6, (IV), carries only one meta‐trifluoromethyl‐substituted phenyl ring, with one of the two trifluoromethyl groups disordered over two positions. In addition to compounds (I)–(IV), the structure of bis[2,6‐bis(trifluoromethyl)phenyl]fluoroborane, C16H6BF13, (V), is presented. None of the ortho‐trifluoromethyl groups is disordered in any of the five compounds. In all the structures, the boron centre is in a trigonal planar coordination. Nevertheless, the bond angles around this atom vary according to the bulkiness and mutual repulsion of the substituents of the phenyl rings. Also, the ortho‐trifluoromethyl‐substituted phenyl rings usually show longer B—C bonds and tend to be tilted out of the BC3 plane by a higher degree than the phenyl rings carrying ortho H atoms. A comparison with related structures corroborates the conclusions regarding the geometric parameters of the boron centre drawn from the five structures in this paper. On the other hand, CF3 groups in meta positions do not seem to have a marked effect on the geometry involving the boron centre. Furthermore, it has been observed for the structures reported here and those reported previously that for CF3 groups in ortho positions of the aromatic ring, disorder of the F atoms is less probable than for CF3 groups in meta or para positions of the ring. 相似文献
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In this paper, we report the green synthesis of 1-(4-ferrocenylbutyl)piperazine chemically grafted rGO (P.Fc/rGO) as a battery-type supercapacitor electrode material. For this purpose, initially, the ability of the aqueous Damson fruit extract is investigated in the reduction reaction of graphene oxide (GO). 1-(4-ferrocenylbutyl)piperazine (P.Fc) is synthesized via nucleophilic substitution reaction of piperazine with as-synthesized 4-chlorobutylferrocene. In continue, P. Fc is incorporated to GO by ring-opening reaction of epoxide groups on the GO surface. In the next step, the modified reduction method by aqueous Damson fruit extract was used to prepare the P.Fc/rGO from P.Fc/GO. The prepared materials were characterized by various techniques including FT-IR, Uv–vis, XRD, SEM, EDX, and BET. N2 adsorption–desorption data of P.Fc/rGO nanocomposite shows that the surface area is 37.746 m2 g−1. The capability of P.Fc/rGO nanocomposite for using as an energy storage electrode material in battery-type supercapacitor was examined by investigation of its electrochemical behavior by CV, EIS, and GCD measurements. The charge storage capacity of 1,102 mAh g−1 is achieved at 2.5 A g−1. This nanocomposite shows 89% retention of charge storage capacity after 2000 CV cycles. 相似文献
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Amir Chamaani Ehsan Marzbanrad Mohammad Reza Rahimipour Maziar S. Yaghmaee Alireza Aghaei Reza Darvishi Kamachali Yashar Behnamian 《Journal of nanoparticle research》2011,13(11):6059-6067
In this study, the authors first review the previously developed, thermodynamics-based theory for size dependency of the cohesion
energy of free-standing spherically shaped Al nanoparticles. Then, this model is extrapolated to the cubic and truncated octahedron
Al nanoparticle shapes. A series of computations for Al nanoparticles with these two new shapes are presented for particles
in the range of 1–100 nm. The thermodynamics computational results reveal that there is a second critical size around 1.62
and 1 nm for cubes and truncated octahedrons, respectively. Below this critical size, particles behave as if they consisted
only of surface-energy-state atoms. A molecular dynamics simulation is used to verify this second critical size for Al nanoparticles
in the range of 1–5 nm. MD simulation for cube and truncated octahedron shapes shows the second critical point to be around
1.63 and 1.14 nm, respectively. According to the modeling and simulation results, this second critical size seems to be a
material property characteristic rather than a shape-dependent feature. 相似文献
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In this paper, we consider the problem of testing a simple hypothesis about the mean of a fuzzy random variable. For this
purpose, we take a distance between the sample mean and the mean in the null hypothesis as a test statistic. An asymptotic
test about the fuzzy mean is obtained by using a central limit theorem. The asymptotical distribution is ω
2-distribution. The ω
2-distribution is only known for special cases, thus we have considered random LR-fuzzy numbers. In the fuzzy concept, in addition to the existence of several versions of the central limit theorem, there
is another practical disadvantage: The limit law is, in most cases, difficult to handle. Therefore, the central limit theorem
for fuzzy random variable does not seem to be a very useful tool to make inferences on the mean of fuzzy random variable.
Thus we use the bootstrap technique. Finally, by means of a simulation study, we show that the bootstrap method is a powerful
tool in the statistical hypothesis testing about the mean of fuzzy random variables. 相似文献
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Ibrahim Tekin Yashar T. Mehraliyev Mansur I. Ismailov 《Mathematical Methods in the Applied Sciences》2019,42(10):3739-3753
In this paper, an initial boundary value problem for nonlinear Klein‐Gordon equation is considered. Giving an additional condition, a time‐dependent coefficient multiplying nonlinear term is determined, and existence and uniqueness theorem for small times is proved. The finite difference method is proposed for solving the inverse problem. 相似文献
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Katz CE Ribelin T Withrow D Basseri Y Manukyan AK Bermudez A Nuera CG Day VW Powell DR Poutsma JL Aubé J 《The Journal of organic chemistry》2008,73(9):3318-3327
The influence of attractive, nonbonded interactions on the reactions of 1,2- and 1,3-hydroxyalkyl azides with ketones has been investigated through experimental and computational means. A series of 1,3-hydroxyalkyl azides bearing electronically tuned aromatic groups at the 2 position were prepared and reacted along with several derivatives designed to conformationally restrict the rotational orientation of the aromatic substituent. These studies showed that a cation-pi interaction between an aryl moiety and an N2(+) leaving group plays a role in determining the stereoselectivity of these reactions. A series of ab initio calculations supported this hypothesis. A computational and experimental analysis suggested a primarily steric model for the analogous reactions of substituted 2-azido-1-ethanol analogues. 相似文献
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The aim of this paper is to survey interlaboratory studies of performance data to produce highly permeable thin‐film composite (TFC) polyamide nanofiltration (NF) membrane in the form of flat sheet at bench scale. TFC polyamide NF membranes were fabricated via interfacial polymerization of 1,3‐phenylenediamine and trimesoyl chloride on porous polyethersulfone (PES) membrane. The NF membranes were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and cross‐flow filtration. The AFM and SEM analyses indicated that a rough and dense film was formed on the PES support membrane. The permeability and NaCl rejection of the NF membrane prepared at the presence of camphor sulfonic acid as pH regulator and triethylamine as accelerator in the aqueous solution were 21 l m?2 h?1 and 70%, respectively. In order to estimate the repeatability and reproducibility standard deviations, the development of an interlaboratory study was conducted by measurements of permeation flux and salt rejection of the synthesized membranes. Repeatability standard deviation of the permeation flux data for the membrane based on optimum formulation was 1.99, and reproducibility standard deviation was 3.55. Also based on this trend, repeatability standard deviation of the salt rejection data was 1.57, and reproducibility standard deviation was 4.11. The American Society for Testing and Materials standard E691‐05 was used for data validation of the repeatability and reproducibility standard deviations and consistency statistics. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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All-optical coherent control of optical bistability(OB) and optical multistability(OM) in the 4.8 nm Zn Se single-quantum well based on excitons and biexciton transitions is investigated. By applying a pair of phase-locked laser pulses all-optical coherent control can be obtained. Theoretical analysis with density matrix and Maxwell equations then yield the optical bistability and optical multistability. It is shown that by controlling the coherent and incoherent processes, the intensity threshold of OB and OM can be modified. Also, it is found that the switching between OB and OM or vice versa can be occurred for some controllable parameters. 相似文献