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81.
Palladium(II)-catalyzed oxidative cyclization of methyl 2-allyl-4,5,6-tribromo-3-hydroxybenzoate 4 gave a mixture of methyl 5,6,7-tribromo-2-methyl-benzofuran-4-carboxylate 5 and methyl 6,7,8-tribromo-2H-1-benzopyran-5-carboxylate 6; the ratio of the two products varied between 71:29 and 24:76 depending on the reaction conditions. On the other hand, NBS or NIS mediated cyclization of 4 followed by treatment with NaOMe or DBU furnished benzofuran derivative 5 in good overall yield. 相似文献
82.
Self‐diffusion and interactions in mixtures of imidazolium bis(mandelato)borate ionic liquids with polyethylene glycol: 1H NMR study 下载免费PDF全文
Andrei Filippov Nail Azancheev Mamoun Taher Faiz Ullah Shah Sergei Glavatskih Oleg N. Antzutkin 《Magnetic resonance in chemistry : MRC》2015,53(7):493-497
We used 1H nuclear magnetic resonance pulsed‐field gradient to study the self‐diffusion of polyethylene glycol (PEG) and ions in a mixture of PEG and imidazolium bis(mandelato)borate ionic liquids (ILs) at IL concentrations from 0 to 10 wt% and temperatures from 295 to 370 K. PEG behaves as a solvent for these ILs, allowing observation of separate lines in 1H NMR spectra assigned to the cation and anion as well as to PEG. The diffusion coefficients of PEG, as well as the imidazolium cation and bis(mandelato)borate (BMB) anion, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state, while the lifetimes of the associated states of the ions and ions with PEG are less than ~30 ms. Generally, increasing the concentration of the IL leads to a decrease in the diffusion coefficients of PEG and both ions. The diffusion coefficient of the anion is less than that of the cation; the molecular mass dependence of diffusion of ions can be described by the Stokes–Einstein model. NMR chemical shift alteration analysis showed that the presence of PEG changes mainly the chemical shifts of protons belonging to imidazole ring of the cation, while chemical shifts of protons of anions and PEG remain unchanged. This demonstrated that the imidazolium cation interacts mainly with PEG, which most probably occurs through the oxygen of PEG and the imidazole ring. The BMB anion does not strongly interact with PEG, but it may be indirectly affected by PEG through interaction with the cation, which directly interacts with PEG. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
83.
Faiz JA Williams RM Silva MJ De Cola L Pikramenou Z 《Journal of the American Chemical Society》2006,128(14):4520-4521
A Ru(II) complex, Ru(alpha2beta), with a trisbipyridyl core and two different receptor sites, alpha- and beta-cyclodextrins, acts as a junction to recognize photoactive guests based on anthracene, Anth, and Os(II), Os-ada, in aqueous solution. Upon light excitation of the self-assembled system Anth.Ru(alpha2beta).Os-ada, an energy cascade process takes place from the Anth guest to the Ru(alpha2beta) core, and subsequently, the energy is funneled to the Os-ada guest. The rates of the two photoinduced processes are determined by time-resolved emission and transient absorption spectroscopic techniques. The system introduces a directed self-assembly approach to unidirectional wires that can lead to nanosized arrays by judicious selection of the individual components. 相似文献
84.
Hotze AC Faiz JA Mourtzis N Pascu GI Webber PR Clarkson GJ Yannakopoulou K Pikramenou Z Hannon MJ 《Dalton transactions (Cambridge, England : 2003)》2006,(24):3025-3034
Ruthenium(II) pyridylimine complexes are explored for their potential as units that might be incorporated into electronic or photonic arrays. The complexes [Ru(bipy)2(L)][PF6]2 (1) and [Ru(tpy)(L)Cl][BF4] (2) with L = phenylpyridin-2-ylmethylene-amine are synthesized and fully characterised using X-ray diffraction analysis and (2D) NMR spectroscopy. 1 displays emission in the far-red area of the spectrum at room temperature. The emission is significantly shifted to longer wavelength with respect to [Ru(bpy)3]2+ indicating that the lowest MLCT state is localised on the pyridylimine ligand. 2 is non-emissive at room temperature and at 77 K. 相似文献
85.
Synthesis of zirconia‐incorporated titania layer by microarc oxidation for biomedical applications 下载免费PDF全文
The structural features, biocompatibility, and mechanical performance of a titania (TiO2) layer with incorporated zirconia (ZrO2) formed by microarc oxidation on commercially pure titanium have been examined in the present study. In comparison to the ZrO2‐free TiO2 layer, the ZrO2‐incorporated oxide layer was dense and contained ZrTiO4 as a new oxide as well as ZrO2 particles. Associated changes in the microstructure enhanced the mechanical durability of TiO2 layer. Owing to the incorporation of identical biocompatible compounds and almost similar surface roughness, no remarkable difference in bioactivities of the ZrO2‐free and ZrO2‐incorporated oxide layers was detected after simulated body fluid tests. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
86.
S. Waheed Y. Faiz S. Rahman N. Siddique 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):143-150
Geophagy of multani mitti (MM) clay is very common in central Pakistan especially amongst women. It was therefore mandatory to establish baseline levels of toxic elements in this clay for its safe dietary consumption by consumers of different genders, age groups and physical states. Instrumental neutron activation analysis and atomic absorption spectrometry techniques were used to determine the nutritional safety of MM clay for oral intake. All quantified toxic elements were detected at trace levels with composition in the descending order; Pb > Br > As > Sb > Hg > Cd. Comparison of these elements in MM clay with other clays shows that As, Cd, and Pb, are lowest in MM clay while its Br and Hg contents are high. Highest weekly dietary intakes of As, Br, Cd, Hg, and Sb were found to be 18, 0.05, 1.6, 9.2 and 1.1 % of the respective recommended provisional tolerable weekly intakes. The findings of this study show that As, Br, Cd, Hg and Sb in MM clay are well below the tolerance levels. However its Pb concentration is very high and may pose health concerns. The data presented in this study can be used as national base level guideline for geophagy of MM clay by men, women (normal, pregnant and lactating) and children. 相似文献
87.
S. Waheed S. Rahman N. Siddique Y. Faiz 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1453-1461
Eleven chelated calcium supplements intended for human consumption and produced by national and multinational companies have been studied for their mineral contents. Instrumental neutron activation analysis technique was used to quantify 12 elements (As, Br, Ce, Co, Cr, Fe, K, Na, Sb, Sn, Sr and Zn) while atomic absorption spectrometry technique quantified Cd, Cu and Ni. Three different irradiation protocols were adopted using a 27 kW tank-in-pool type miniature neutron source reactor. Most of the elements were present as minor or trace constituents except for Na that was quantified as major element in CaS-1 (3.73 %), CaS-2 (1.45 %), CaS-4 (1.56 %), CaS-5 (2.31 %), CaS-6 (1.84 %), CaS-7 (1.22), CaS-8 (1.73), CaS-9 (1.94), CaS-10 (2.07) and CaS-11 (2.48). However supplement CaS-3 with Ca source of calcium acetate contained only 53 μg/g of Na and the highest amount of Fe while As, Br, Cd and Sb were not detected in this sample. Percentage daily intakes with respect to their recommended dietary reference intake s and provisional tolerable daily intakes of essential and toxic elements showed that these elements contribute to a very low percentage of the recommended/tolerable levels for most of the supplements studied. Nevertheless the findings depict that it is very important for pharmaceutical and neutraceutical firms to completely identify these elements in the supplements and include their potency on the labels before being released to the consumers. 相似文献
88.
Nik Akmar Rejab Mohamadariff Othman Wan Fahmin Faiz Wan Ahmad Mohd Fadzil Ain Zainal Arifin Ahmad 《Journal of Sol-Gel Science and Technology》2011,57(2):172-177
In this paper, we report the application of Neodymium (Nd) doped barium titanate thin films (Ba1-xNdx) TiO3 with x = 0 and 0.07 as dielectric resonator antenna. The films were prepared using the sol–gel method and dip-coating technique.
Barium acetate, titanium (IV) isopropoxide and neodymium (III) acetate hydrate were used as precursors while glacial acetic
acid and acetylacetone were used as solvents. Si wafers were used as a substrate with dipping times varying from 10, 30, and
50 s. The 0.07 films were >800 nm thick and crystallized after being annealed at 800°C for 30 min. The films were tested as
dielectric resonator antenna. It was found that, on the actual antenna circuit, the resonant frequency decreased as the (Ba0.93Nd0.07) TiO3 films thickness increased (from 0.8379, to 5.4525 μm). All samples resonate in the range of 8.68–8.83 GHz with quasi omni-directional
radiation patterns. 相似文献
89.
Nguyen Thi Hoai Phuong Hoang Tuy Faiz Al-Khayyal 《Computational Optimization and Applications》2006,35(2):135-159
A problem arising in the control of flutter in compression systems via mistuning is formulated as maximizing a quadratic function
with a circulant matrix over a set of vectors whose every component can take one of three values (the three level problem)
or one of two values (the two level problem). 相似文献
90.
[reaction: see text] Unprecedented molecular rearrangements during diazomethane-mediated reaction of norbornyl alpha-ketohemiketals leading to novel molecular entities are presented. A dramatic change in the reaction outcome was noted for five- and six-membered alpha-ketohemiketals: the former predominantly furnished rearranged bicyclic products involving migration of the gamma-alkoxy group, and the latter furnished the oxetane derivative as the major product. Interestingly, six-membered O-methyl-ketal yielded a product arising from the migration of the vicinal alkoxy group. 相似文献