排序方式: 共有88条查询结果,搜索用时 15 毫秒
51.
Dr. Andrew G. Crawford Prof. Dr. Zhiqiang Liu Prof. Dr. Ibraheem A. I. Mkhalid Dr. Marie‐Hélène Thibault Dr. Nicolle Schwarz Dr. Gilles Alcaraz Dr. Andreas Steffen Dr. Jonathan C. Collings Dr. Andrei S. Batsanov Prof. Dr. Judith A. K. Howard Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):5022-5035
An efficient synthetic route to 2‐ and 2,7‐substituted pyrenes is described. The regiospecific direct C? H borylation of pyrene with an iridium‐based catalyst, prepared in situ by the reaction of [{Ir(μ‐OMe)cod}2] (cod=1,5‐cyclooctadiene) with 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine, gives 2,7‐bis(Bpin)pyrene ( 1 ) and 2‐(Bpin)pyrene ( 2 , pin=OCMe2CMe2O). From 1 , by simple derivatization strategies, we synthesized 2,7‐bis(R)‐pyrenes with R=BF3K ( 3 ), Br ( 4 ), OH ( 5 ), B(OH)2 ( 6 ), and OTf ( 7 ). Using these nominally nucleophilic and electrophilic derivatives as coupling partners in Suzuki–Miyaura, Sonogashira, and Buchwald–Hartwig cross‐coupling reactions, we obtained 2,7‐bis(R)‐pyrenes with R=(4‐CO2C8H17)C6H4 ( 8 ), Ph ( 9 ), C≡CPh ( 10 ), C≡C[{4‐B(Mes)2}C6H4] ( 11 ), C≡CTMS ( 12 ), C≡C[(4‐NMe2)C6H4] ( 14 ), C≡CH ( 15 ), N(Ph)[(4‐OMe)C6H4] ( 16 ), and R=OTf, R′=C≡CTMS ( 13 ). Lithiation of 4 , followed by reaction with CO2, yielded pyrene‐2,7‐dicarboxylic acid ( 17 ), whilst borylation of 2‐tBu‐pyrene gave 2‐tBu‐7‐Bpin‐pyrene ( 18 ) selectively. By similar routes (including Negishi cross‐coupling reactions), monosubstituted 2‐R‐pyrenes with R=BF3K ( 19 ), Br ( 20 ), OH ( 21 ), B(OH)2 ( 22 ), [4‐B(Mes)2]C6H4 ( 23 ), B(Mes)2 ( 24 ), OTf ( 25 ), C≡CPh ( 26 ), C≡CTMS ( 27 ), (4‐CO2Me)C6H4 ( 28 ), C≡CH ( 29 ), C3H6CO2Me ( 30 ), OC3H6CO2Me ( 31 ), C3H6CO2H ( 32 ), OC3H6CO2H ( 33 ), and O(CH2)12Br ( 34 ) were obtained from 2 . These derivatives are of synthetic and photophysical interest because they contain donor, acceptor, and conjugated substituents. The crystal structures of compounds 4 , 5 , 7 , 12 , 18 , 19 , 21 , 23 , 26 , and 28 – 31 have also been obtained from single‐crystal X‐ray diffraction data, revealing a diversity of packing modes, which are described in the Supporting Information. A detailed discussion of the structures of 1 and 2 , their polymorphs, solvates, and co‐crystals is reported separately. 相似文献
52.
In the present paper we develop a high algebraic order multistep method. The characteristic property of the new proposed method is the requirement of vanishing the phase-lag and its derivatives. The new method is applied for the approximate solution of the radial Schrödinger equation. The efficiency of the new methodology is proved via error analysis and numerical applications. 相似文献
53.
Ibraheem Othman Ali 《Journal of Thermal Analysis and Calorimetry》2014,116(2):805-816
Nickel ferrite (NiFe2O4) was synthesized using citric acid (CA) as a chelating agent and varying amounts of polyvinyl alcohol (PVA) as powder binder via a combustion process. The influence of PVA/NiFe2O4 blend composition on the phase, crystal structure, and morphology has been investigated by X-ray diffraction (XRD), scanning electron microscopy, and Fourier transform infrared spectroscopy, respectively. The probable assignments of the thermal degradation products of PVA/NiFe2O4 were studied by complementary thermogravimetric analysis and differential thermal analysis. The PVA/NiFe2O4 crystals preferentially oriented along the (311) plane as revealed by XRD, owing to diffusion of α-Fe2O3 particles into the lattice matrix where the rate of diffusion increased significantly with the PVA concentration increase from 0.1 to 0.3 mol%. A vibrational doublet at 1,644 and 1,609 cm?1 for the ≡Fe–O–COOH complex was emitted in the spectra of PVA-impregnated NiFe2O4 to assure the attachment of Fe(III) to the chelating agents CA/PVA. Thermal kinetic consideration based on Coats–Redfern and Horowitz–Metzger equations at subsequent decomposition steps of CA/PVA/NiFe2O4 illustrated that the values of activation free energy ΔG* increase significantly, indicating the non-spontaneous behavior. The one-step direct hydroxylation of benzene toward phenol has been extensively investigated using hydrogen peroxide as an oxidant. 相似文献
54.
In this paper, we develop a new four-step hybrid method of sixth algebraic order with vanished phase-lag and its first and second derivatives. For the obtained method we study: – its error and – its stability We apply the produced method to the Schrödinger equation in order to show its efficiency. 相似文献
55.
Awad A. Ibraheem M. El-Azab Farid Arwa S. Al-Hajjaji 《Brazilian Journal of Physics》2018,48(5):507-512
Angular distributions in the elastic scattering of 8B from 12C and 58Ni targets at different energies have been analyzed in the framework of the double-folding (DF) optical model. The real central part of the nuclear optical potential is obtained by folding the M3Y effective interaction with the cluster density distribution of the 8B nucleus. The experimental angular distributions have been successfully reproduced. This confirms the validity of the cluster structure of the 8B nucleus. 相似文献
56.
A family of tenth algebraic order eight-step methods is constructed in this paper. For this family of methods, we require the phase-lag and its first, second and third derivatives to be vanished. Three alternative methods are proposed which satisfy the above requirements. An error analysis and a stability analysis is also investigated in this paper and a comparison with other methods is also studied. The new proposed methods are applied for the numerical solution of the one dimensional Schrödinger equation. The efficiency of the new methodology is proved via theoretical analysis and numerical applications. 相似文献
57.
The α -target semimicroscopic single folding potentials have been derived by folding a composite (repulsive and attractive) effective α-α interaction with the α -cluster distribution density in the target nuclei. The obtained potentials are considered as the real part of the nuclear optical model potentials, while the imaginary parts are phenomenologicaly expressed using the Woods-Saxon form. Nine sets of measured experimental data of the 4He+12C and 4He+16O elastic rainbow scattering over the energy range 80-240 MeV are analyzed using the obtained potentials. The data are successfully reproduced using the extracted potentials. The resulted reaction cross sections are also investigated and compared with the available corresponding data. 相似文献
58.
Nerapusri V Keddie JL Vincent B Bushnak IA 《Langmuir : the ACS journal of surfaces and colloids》2007,23(19):9572-9577
The addition of cetylpyridinium chloride (CPC) to aqueous dispersions of poly(N-isopropylacrylamide) [poly(NIPAM)] and poly(N-isopropylacrylamide-co-acrylic acid) [poly(NIPAM-co-AAc)] microgel particles leads to absorption of the CPC into the particles and to corresponding changes in their hydrodynamic diameter. With the latter set of particles there is a strong pH dependence. The dependence of both hydrodynamic diameter and electrophoretic mobility of the microgel particles on the added CPC concentration show a strong correlation with CPC uptake, as obtained from direct CPC absorption measurements. Various mechanisms for CPC absorption into the microgel particles are postulated, including electrostatic, polar, and hydrophobic interactions. A comparison has also been made between the effect of added CPC on the hydrodynamic diameter of free microgel particles in dispersion, determined by dynamic light scattering, and the thickness of adsorbed monolayers of the same microgel particles deposited on cationically modified, oxidized silicon surfaces, as determined from ellipsometry measurements. The trends observed in both cases are broadly similar. This work opens the way for development of microgel layers for controlled uptake and release applications. 相似文献
59.
Wameedh Riyadh Abdul-Adheem Ahmed Alkhayyat Ammar K. Al Mhdawi Nik Bessis Ibraheem Kasim Ibraheem Ahmed Ibraheem Abdulkareem Amjad J. Humaidi Arif A. AL-Qassar 《Entropy (Basel, Switzerland)》2021,23(11)
Multi-Inputs-Multi-Outputs (MIMO) systems are recognized mainly in industrial applications with both input and state couplings, and uncertainties. The essential principle to deal with such difficulties is to eliminate the input couplings, then estimate the remaining issues in real-time, followed by an elimination process from the input channels. These difficulties are resolved in this research paper, where a decentralized control scheme is suggested using an Improved Active Disturbance Rejection Control (IADRC) configuration. A theoretical analysis using a state-space eigenvalue test followed by numerical simulations on a general uncertain nonlinear highly coupled MIMO system validated the effectiveness of the proposed control scheme in controlling such MIMO systems. Time-domain comparisons with the Conventional Active Disturbance Rejection Control (CADRC)-based decentralizing control scheme are also included. 相似文献
60.
Yasiru Randika Perera Joanna Xiuzhu Xu Dhanush L. Amarasekara Alex C. Hughes Ibraheem Abbood Nicholas C. Fitzkee 《Molecules (Basel, Switzerland)》2021,26(19)
Polyethylene glycol (PEG) surface conjugations are widely employed to render passivating properties to nanoparticles in biological applications. The benefits of surface passivation by PEG are reduced protein adsorption, diminished non-specific interactions, and improvement in pharmacokinetics. However, the limitations of PEG passivation remain an active area of research, and recent examples from the literature demonstrate how PEG passivation can fail. Here, we study the adsorption amount of biomolecules to PEGylated gold nanoparticles (AuNPs), focusing on how different protein properties influence binding. The AuNPs are PEGylated with three different sizes of conjugated PEG chains, and we examine interactions with proteins of different sizes, charges, and surface cysteine content. The experiments are carried out in vitro at physiologically relevant timescales to obtain the adsorption amounts and rates of each biomolecule on AuNP-PEGs of varying compositions. Our findings are relevant in understanding how protein size and the surface cysteine content affect binding, and our work reveals that cysteine residues can dramatically increase adsorption rates on PEGylated AuNPs. Moreover, shorter chain PEG molecules passivate the AuNP surface more effectively against all protein types. 相似文献