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61.
Density functional theory calculations have been carried out to investigate the [2?+?x] x?=?1, 2, and 3 cycloaddition reactions (paths A, B, and C) of triatomic sulfur (S3) with the C70 fullerene in terms of geometry, energies, and electronic structures. The thiozonation (S3) on the hexagon–hexagon and hexagon–pentagon bonds of the C70 fullerene through 1,3-dipolar reaction, i.e., [2?+?3] cycloaddition, is generally exothermic, while through the chelotrope additions, i.e., [2?+?1] cycloaddition, are endothermic. The results indicate that the 1,3-dipolar cycloaddition is the most preferable path. Having more negative values of reaction energies Er together with the lower barrier heights, thiozonation of the hexagon–hexagon bonds is thermodynamically and kinetically more favorable than hexagon–pentagon ones. Moreover, the addition of thiozone to the hexagon–hexagon bonds near the pole area of the C70 leads to more negative reaction energies. Therefore, it is established that the arrangement and position of C=C bonds play an important role in the thiozonation of C70 fullerene. Thiozonolysis of triatomic sulfur (S3) indicates that S–S bond cleavage has not occurred, instead a sulfur bridge over a C–C bond or a four-membered ring of 1,2-dithietane-1-sulfide is preferred to be formed. 相似文献
62.
Structural investigations of deuterated liquid formamide were performed by using neutron scattering, ab-initio calculations and classical Molecular Dynamics (MD) simulations. The recorded neutron data are analysed to yield the total structure factor SM (Q), the molecular form factor F (Q), the distinct pair correlation function gL(r) and particularly the deuterium-oxygen signature of H-bond interactions. Neutron scattering data, as well as recent x-ray studies, clearly show that the local order of the liquid is largely described by one dimer, two trimers and one tetramer. Molecular Dynamics simulations show that neutron scattering data can be reproduced by three different force fields. 相似文献
63.
Mohammad Anary-Abbasinejad Fereshteh Nejad-Shahrokhabadi 《Phosphorus, sulfur, and silicon and the related elements》2020,195(8):660-665
AbstractA three-component reaction between barbituric/thiobarbituric acid, phosphines, and dialkyl acetylenedicarboxylates in dry acetonitrile led to the formation of barbiturate/thiobarbiturate-functionalized stable zwitterionic salts in a one-pot process. When trialkyl phosphites were used instead of phosphines, barbiturate/thiobarbiturate-functionalized phosphonates were obtained in good yields. 相似文献
64.
Tülay. Bal. Demirci Yüksel Köseoğlu Sadik Güner Bahri Ülküseven 《Central European Journal of Chemistry》2006,4(1):149-159
Four new oxovanadium(IV) compounds were prepared by template reaction of salicyl-, 5-bromosalicyl-and 3-methoxysalicyl-aldehyde
S-methylthiosemicarbazones with 2-hydroxy-, 5-bromo-2-hydroxy-and 3-methoxy-2-hydroxy-benzaldehyde in various combinations.
The compounds were isolated as stable solid compounds with general formula [VO(L)] and characterized by elemental analysis,
conductivity and magnetic measurements, electronic, IR and EPR spectroscopy. The X-band EPR signals recorded from powder forms
of all samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around
the paramagnetic vanadium ions. The anisotropic Lande splitting factors take values of g‖ < g⊥ < ge = 2.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters.
The EPR spectra recorded from solution forms almost have isotropic character. 相似文献
65.
Mahdieh Khatiri Fereshteh Hajiesmaeilbaigi Hosein Razaghi Ali Panahpour Alireza Bananej 《Optical and Quantum Electronics》2018,50(8):312
In this work, nano-porous anti-reflective silica thin films are deposited on the quartz samples by dip-coating in silica sol–gel. After dip-coating, the samples are divided into three groups and each group is heated in an oven with a different drying method. The effect of the heating methods on the morphology and optical properties of the coated layers are studied by SEM imaging and measuring optical transmission of the samples. Then based on the transmission data and calculation of absorption coefficient of the layers, the band gap energy of the silica thin films is calculated. In addition, laser induced damage threshold (LIDT) of the samples are measured by using 35 fs, 100 mJ femtosecond laser pulses. It can be seen that there is a distinct correlation between band gap energy and LIDT of the samples which both of them have been affected by heating method of the coated samples. 相似文献
66.
CuI‐functionalized halloysite nanoclay as an efficient heterogeneous catalyst for promoting click reactions: Combination of experimental and computational chemistry 下载免费PDF全文
Amine‐functionalized halloysite nanotubes (HNTs‐2 N) were prepared and further modified by introduction of salicylaldehyde and formation of imine functionality (HNTs‐2 N‐Sal). The latter was subsequently used for immobilization of CuI and formation of CuI@HNTs‐2 N‐Sal, which could effectively promote click reactions of terminal alkynes, sodium azide and α‐haloketones or alkyl halides in aqueous media and under mild reaction conditions to afford 1,2,3‐triazoles in relatively short reaction times. Notably, the catalyst could be recycled in up to six reaction runs with negligible loss of catalytic activity and CuI leaching. Also, the geometry of CuI adsorption on the modified HNTs surface was explored by molecular simulation with density functional theory. Furthermore, topographic steric maps of possible coordination modes were obtained using the recently released SambVca2 web application tool. Based on obtained results, a catalytic site with superior performance was suggested. 相似文献
67.
Tungstate supported mesoporous silica SBA‐15 with imidazolium framework as a hybrid nanocatalyst for selective oxidation of sulfides in the presence of hydrogen peroxide 下载免费PDF全文
Alireza Sedrpoushan Fereshteh Hosseini‐Eshbala Farajollah Mohanazadeh Masoud Heydari 《应用有机金属化学》2018,32(2)
In this work, a new heterogeneous catalyst (SBA‐15/Im/WO42?) was prepared, and then its performance in the oxidation of organic sulfides was studied (using 30% H2O2 as green oxidant under neutral reaction conditions). This organic–inorganic hybrid mesoporous material was characterized by various techniques, such as FT‐IR, inductively coupled plasma, X‐ray powder diffraction, high‐resolution‐transmission electron microscopy, N2 adsorption–desorption and thermogravimetric analysis. The catalyst was also applied to the selective oxidation of various sulfides. The hybrid catalyst was easily recovered, and was very stable and retained good activity for at least five successive runs without any additional activation. Moreover, there was no remarkable decrease in the activity and selectivity of the catalyst. The products could be easily isolated by just removing the solvent after filtering the catalyst. The yields of the catalytic productions through this catalyst were in the range from 75% to 97%. 相似文献
68.
A new man-tailored biomimetic sensor for sulfamethoxazole host–guest interactions and potentiometric transduction is presented. The host cavity was shaped on a polymeric surface assembled with methacrylic acid monomers by radical polymerization. Molecularly imprinted particles (MIP) were mixed with graphite powder, paraffin oil and ionic site. Using the Taguchi method, this study analyzed the optimum conditions for preparing the carbon paste electrode. The controllable factors used in this study consisted the weights of (1) MIP, (2) paraffin oil, (3) graphite, and (4) the ionic site. The percentage contribution of each controllable factor was also determined. MIP-modified electrode exhibited a Nernstian response (57.2 mVdecade?1) in a wide concentration range of 6.0 × 10?8 to 3.1 × 10?3 mol L?1 with a lower detection limit of 3.5 × 10?9 mol L?1. The sensor was successfully applied to the determination of sulfamethoxazole concentrations in foods and plasma. 相似文献
69.
Fereshteh Ahmadi Zeinab Noroozi TissehMinoo Dabiri Ayoob Bazgir 《Comptes Rendus Chimie》2013,16(12):1086-1090
A practical and efficient method for the synthesis of 1,2,3-triazoles via the cycloaddition reaction of azides and CH-acids in the presence of 1,1,3,3-tetramethylguanidine (TMG) in ethanol at 30 °C has been reported. The simple experimental procedure, short reaction times, and good yields are the advantages of the present method. 相似文献
70.
We study the windowed Fourier transform in the framework of Clifford analysis, which we call the Clifford windowed Fourier
transform (CWFT). Based on the spectral representation of the Clifford Fourier transform (CFT), we derive several important
properties such as shift, modulation, reconstruction formula, orthogonality relation, isometry, and reproducing kernel. We
also present an example to show the differences between the classical windowed Fourier transform (WFT) and the CWFT. Finally,
as an application we establish a Heisenberg type uncertainty principle for the CWFT. 相似文献