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991.
992.
Shyamaprosad Goswami Abhishek Manna Sima Paul Avijit K. Das Prasanta K. Nandi Anup Kumar Maity Partha Saha 《Tetrahedron letters》2014
5(Benzothiazol-2-yl)-4-hydroxyisophthalaldehyde (BHI), an intense ESIPT containing molecule in mixed media loses its properties due to resonance-assisted H-bond (RAHB) in absolute water. Due to resonance-assisted H-bond the o-aldehyde is more reactive than the other one. With addition of cysteine/homocysteine into this solution the o-aldehyde group gets transformed into thiazolidine/thiazine ring, respectively, and the phenolic proton becomes free enough for transfer to nitrogen of the benzothiazole ring in excited state, that is, the ESIPT of BHI is turned on. Thus we can detect cysteine/homocysteine in water as well as in live cells. 相似文献
993.
994.
Aromatic substituents migrate in a novel oxidative cyclization mediated by iodine(III) reagents. 4-Arylbut-3-enoic acids are cyclized and rearranged to 4-arylfuran-2(5H)-ones by hypervalent iodine compounds in good to excellent yields under mild reaction conditions. Other ring sizes are also accessible. The mechanism of the reaction is described in detail, and calculations highlight the cationic nature of the intermediates in the rearrangement. The fast access to heavily substituted furanones is used for the synthesis of biologically active derivatives. 相似文献
995.
996.
Anshu Dandia Ruby Singh Dharmendra Singh Ashok Laxkar Asha Sivpuri 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2472-2479
A dry media procedure has been developed for the synthesis of a series of new class of pyrazolo [4,3-c][1,5]benzothiazepines 6 under microwave irradiation using montmorillonite K10 as solid support. The catalyst can be recovered and reused. Thus, the procedure provides a simple and green synthetic methodology under environmentally friendly conditions. Antifungal screening of synthesized compounds has shown promising activity. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
997.
Dr. Mohd Nazish Dr. Mujahuddin M. Siddiqui Dr. Samir Kumar Sarkar Dr. Annika Münch Christina M. Legendre Dr. Regine Herbst-Irmer Prof. Dietmar Stalke Prof. Dr. Herbert W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1744-1752
This work describes the synthesis and coordination behavior of a new mixed-donor ligand PhC(NtBu)2SiC6H4PPh2 ( 1 ) containing both silylene and phosphine donor sites. Ligand 1 was synthesized from a reaction of ortho-lithiated diphenylphosphinobenzene (LiC6H4PPh2) with chlorosilylene (PhC(NtBu)2SiCl). Treatment of 1 with Se and GeCl2 resulted in SiIV compounds 2 and 3 by selective oxidation of the silylene donor. This strong σ-donor ligand induces dissociation of CuCl and PhBCl2 leading to formation of ionic complexes 4 and 5 respectively. The reaction of 1 with ZnCl2 and AlCl3 resulted in the formation of chelate complexes 5 and 7 , respectively, while treatment with EtAlCl2 and GaCl3 forms monodentate complexes 8 and 9 . X-ray analysis of 4 showed that the copper is in the spiro center of the two five-membered rings. Moreover, the copper(I)chloride has not been oxidized but dissociates to Cu+ and [CuCl2]−. All the compounds are well characterized by mass spectrometry, elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction studies. 相似文献
998.
We present a study of the magnetic properties of Co nanoparticles having a combination of both spherical and disk shapes. The hcp Co nanospheres with an average diameter of 11 nm and nanodiscs of dimensions ∼2.5×15 nm2 were prepared by thermal decomposition of di-cobalt octacarbonyl in the presence of an amine surfactant. The as-synthesized nanoparticles were oxidized to grow an antiferromagnetic layer. High resolution transmission electron microscopy showed the presence of a ferromagnet/antiferromagnet (Co/CoO) interface with a 2.2-nm thick CoO shell on the spherical nanoparticles and 0.5 nm thick on nanodiscs. We report the temperature and field dependent DC magnetization, frequency, field, and temperature dependent AC susceptibility, and the radio frequency transverse susceptibility. A low temperature paramagnetic behavior was observed in the DC magnetization at high fields and is assigned to defects in the CoO shell that are not coupled to the antiferromagnetic lattice. Our results support the existence of a low temperature frozen, disordered magnetic state, characterized by a strong exchange coupling between the structurally disordered, spin-glass CoO shell and Co core. 相似文献
999.
1000.
V. Singh V. K. Rai S. Watanabe T. K. Gundu?Rao I. Ledoux-Rak H.-Y. Kwak 《Applied physics. B, Lasers and optics》2010,101(3):631-638
The Er3Al5O12 phosphor powders were prepared using the solution combustion method. Formation and homogeneity of the Er3Al5O12 phosphor powders have been verified by X-ray diffraction and energy-dispersive X-ray analysis respectively. The frequency
up-conversion from Er3Al5O12 phosphor powder corresponding to the 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, 4F9/2 → 4I15/2 and the infrared emission (IR) due to the 4I13/2 → 4I15/2 transitions lying at ∼410, ∼524, ∼556, 645–680 nm and at ∼1.53 μm respectively upon excitation with a Ti-Sapphire pulsed/CW
laser have been reported. The mechanism responsible for the frequency up-conversion and IR emission is discussed in detail.
Defect centres induced by radiation were studied using the techniques of thermoluminescence and electron spin resonance. A single
glow peak at 430°C is observed and the thermoluminescence results show the presence of a defect center which decays at high
temperature. Electron spin resonance studies indicate a center characterized by a g-factor equal to 2.0056 and it is observed
that this center is not related to the thermoluminescence peak. A negligibly small concentration of cation and anion vacancies
appears to be present in the phosphor in accordance with the earlier theoretical predictions. 相似文献