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排序方式: 共有532条查询结果,搜索用时 17 毫秒
11.
Gao J Yu A Itkis ME Bekyarova E Zhao B Niyogi S Haddon RC 《Journal of the American Chemical Society》2004,126(51):16698-16699
Aligned single-walled carbon nanotubes (SWNTs) and hierarchical SWNT assembly were fabricated by electrospinning. The high fiber elongation and high DC electric field applied during the electrospinning process result in the orientation of the SWNTs along the axial direction of the fiber. The alignment of the electropsun composite fiber transfers this local SWNT orientation to macroscopically aligned SWNTs. After removing the polymer component from the aligned composite fiber, we produced large area aligned SWNTs. The results show that the directional control of SWNT alignment and debundling of SWNTs into individual tubes can be simultaneously realized. 相似文献
12.
Kritika Keshari Moumita Bera Lucía Velasco Sandip Munshi Geetika Gupta Dooshaye Moonshiram Sayantan Paria 《Chemical science》2021,12(12):4418
A terminal FeIIIOH complex, [FeIII(L)(OH)]2− (1), has been synthesized and structurally characterized (H4L = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene). The oxidation reaction of 1 with one equiv. of tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBAH) or ceric ammonium nitrate (CAN) in acetonitrile at −45 °C results in the formation of a FeIIIOH ligand radical complex, [FeIII(L˙)(OH)]− (2), which is hereby characterized by UV-visible, 1H nuclear magnetic resonance, electron paramagnetic resonance, and X-ray absorption spectroscopy techniques. The reaction of 2 with a triphenylcarbon radical further gives triphenylmethanol and mimics the so-called oxygen rebound step of Cpd II of cytochrome P450. Furthermore, the reaction of 2 was explored with different 4-substituted-2,6-di-tert-butylphenols. Based on kinetic analysis, a hydrogen atom transfer (HAT) mechanism has been established. A pKa value of 19.3 and a BDFE value of 78.2 kcal/mol have been estimated for complex 2.One-electron oxidation of an FeIII–OH complex (1) results in the formation of a FeIII–OH ligand radical complex (2). Its reaction with (C6H5)3C˙ results in the formation of (C6H5)3COH, which is a functional mimic of compound II of cytochrome P450. 相似文献
13.
L. H. Klemm Susan Johnstone Sandip K. Sur Daniel R. Muchiri 《Journal of heterocyclic chemistry》1989,26(5):1277-1281
Three compounds, thieno[3,2-b]pyridine 4-oxide, 7-nitrothieno[3,2-b]pyridine 4-oxide ( 1 c), and 6-cyano-thieno[2,3-b]pyridine, undergo nitration by means of a mixture of nitric and sulfuric acids to yield 3,7-dinitro-thieno[3,2-b]pyridine (3%), 3,7-dinitrothieno[3,2-b]pyridine 4-oxide ( 1d ) (26%), and 6-carbamoyl-5-nitrothieno[2,3-b]pyridine ( 6b ) (11%), respectively. Structures of the products were ascertained by spectral means, notably infrared, 1H nmr, and 13C nmr. It is proposed that 1d exists (at least in part) as a tricyclic structure and that 6b may result from an intramolecular mechanism of nitration. An attempt to de-N-oxygenate 1c with excess triphenylphosphine removes more than one oxygen atom per molecule (as triphenylphosphine oxide) without producing an identified thienopyridine product. 相似文献
14.
Sumanta Bhattacharya Sandip K. Nayak Subrata Chattopadhyay Manas Banerjee 《Journal of solution chemistry》2006,35(4):485-506
Supramolecular complexes of [60]- and [70]fullerenes with various meso-tetraphenylporphyrins in toluene solutions have been studied by electronic absorption spectroscopy. Charge transfer (CT) absorption bands are observed in the visible region. Vertical ionization potentials (I
D
V) of the meso-tetraphenylporphyrins are reported from a study of EDA interaction of these porphyrins with a number of electron acceptors like o-chloranil, p-chloranil, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and vitamin K. The dependence of the CT transition energy on the donor ionization potential has been utilized to estimate the vertical electron affinities (E
A
V) of [60]- and [70]fullerenes in solution. The value of E
A
V for [60]fullerene is found to be 0.10 eV lower in magnitude than that of [70]fullerene. We have extracted degrees of CT, and oscillator and transition dipole strengths of the fullerenes/meso-tetraphenylporphyrins complexes. The experimental results show that the CT complexes studied here have a neutral character in their ground states. Electronic coupling elements have been determined for fullerene/meso-tetraphenylporphyrin complexes. Values of the solvent reorganization energy indicate that the electron transfer process takes place at a faster rate in the case of [70]fullerene/meso-tetraphenylporphyrin complexes. 相似文献
15.
16.
Benzoyl peroxide has been used as a mild and efficient reagent for the preparation of benzoyl ester of oxime in moderate to good yields. 相似文献
17.
Sandip Dutta Ritabrata Biswas 《The European Physical Journal C - Particles and Fields》2017,77(10):717
This paper deals with the viscous accretion flow of a modified Chaplygin gas towards a black hole as the central gravitating object. A modified Chaplygin gas is a particular type of dark energy model which mimics of radiation era to phantom era depending on the different values of its parameters. We compare the dark energy accretion with the flow of adiabatic gas. An accretion disc flowing around a black hole is an example of a transonic flow. To construct the model, we consider three components of the Navier–Stokes equation, the equation of continuity and the modified Chaplygin gas equation of state. As a transonic flow passes through the sonic point, the velocity gradient being apparently singular there, it gives rise to two flow branches: one in-falling, the accretion and the other outgoing, the wind. We show that the wind curve is stronger and the wind speed reaches that of light at a finite distance from the black hole when dark energy is considered. Besides, if we increase the viscosity, the accretion disc is shortened in radius. These two processes acting together make the system deviate much from the adiabatic accretion case. It shows a weakening process for the accretion procedure by the work of the viscous system influencing both the angular momentum transport and the repulsive force of the modified Chaplygin gas. 相似文献
18.
19.
A novel protocol for intramolecular ketyl-olefin radical cyclization with low-valent titanium reagent is outlined. It allows the formation of the benzopyran nucleus from ortho-allyloxy propiophenones as the sole product in moderate yields via intramolecular radical cyclization. 相似文献
20.
Shreyans K. Jain Samdarshi Meena Asif K. Qazi Aashiq Hussain Sunil K. Bhola Rajendra Kshirsagar Koteppa Pari Anamika Khajuria Abid Hamid R. Uma Shaanker Sandip B. Bharate Ram A. Vishwakarma 《Tetrahedron letters》2013
The chromone alkaloid dysoline (1), a new regioisomer of rohitukine (2) along with rohitukine and rohitukine-N-oxide (3) were isolated from the stem barks of Dysoxylum binectariferum. The structure of dysoline (1) was determined by extensive 2D-NMR studies and the absolute configuration was established by NOESY and CD spectra. Dysoline (1) consisted of a 5,7-dihydroxy-2-methylchromone nucleus substituted with a 2′-hydroxylated N-Me piperidine ring at the C-6 position. Dysoline differs from rohitukine by the position of the piperidine ring on the chromone nucleus. Dysoline displayed promising cytotoxicity in HT1080 fibrosarcoma cells with an IC50 of 0.21 μM, and also displayed significant inhibition of proinflammatory cytokines TNF-α and IL-6. 相似文献