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排序方式: 共有92条查询结果,搜索用时 31 毫秒
1.
Sharma Narinder Bhatia Sumeet Singh Sharma Vipul Sivia Jagtar Singh 《Wireless Personal Communications》2020,111(3):1977-1997
Wireless Personal Communications - This article presents a microstrip-fed octagonal shaped monopole antenna with dual band notched characteristics for UWB applications. Partial ground plane has... 相似文献
2.
Cory Momany Marvin L. Hackert Jyotsna Sharma Narinder S. Poonia 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):343-354
Sodium salicylate (NaSal where Sal=2-hydroxybenzoate), when mixed with dibenzo-24-crown-8 (DB24C8) yields a bimetallic complex [NaSal]2DB24C8 in most polar organic media, while potassium salicylate (KSal) under similar conditions shows a tendency to yield 11 or 21 complexes depending upon medium or synthesis. However, the presence of both NaSal and KSal together results in a unique mixed cation complex of composition NaKSal2DB24C8. This product melts sharply (190-92°C) without decomposition, displays IR spectral characteristics comparable to those of [Na(Sal)]2DB24C8, and is stable in aqueous media as shown by the detectable cation effect on the UV absorption bands of Sal and DB24C8. Single crystal X-ray analysis of NaK(Sal)2DB24C8 reveals that the system represents a co-crystallization complex of individual (KSal)2DB24C8 and (NaSal)2DB24C8 molecules. The crystals are monoclinic,P21/c,a=19.976(2) Å,b=9.031(1) Å,c=25.541(5) Å,=122.065(9)°, Å3,T=298 K,Z=2+2, CuK =1.5418 Å, and 2 (2.5°–100°). FinalR factor for the 3012 observed reflections (F>3) is 0.092. Both the Na2- and K2-molecules possess crystallographic centers of symmetry with one metal and its associated anion on each side of the crown ring. However, the conformations of the crowns are very different in the two molecules, with the K2-crown being nearly planar and the Na2-crown being quite puckered. Four oxygen atoms from the DB24C8 (KO, 2.680–2.908 Å) and three carboxyl oxygen atoms (KO, 2.472–2.708 Å) from separate salicylate ions coordinate with each potassium. Three oxygens from the crown (NaO, 2.536–2.65 Å) and three carboxyl oxygens (NaO, 2.31–2.563 Å) coordinate with each sodium. The salicylate ions lie on opposite sides and nearly perpendicular (77.2°, Na2-molecule; 82.7° K2-molecule) to each crown but coordinate to both of the metal ions within a molecule. The K+K+ and Na+Na+ distances in the respective molecules are 3.95 and 3.34 Å.
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82044 (18 pages). 相似文献
3.
Baldev Singh Manhas Narinder Kaur Ajaib Singh Dhindsa 《Transition Metal Chemistry》1992,17(4):287-291
New copper(II) acetate complexes with the saturated diheterocyclic bases (L-L): piperazine, 1-methylpiperazine, and 1,4-dimethylpiperazine
and their monohydrochlorides, have been prepared and characterised by physico-chemical and spectroscopic methods. They are
magnetically dilute and antiferromagnetic, with stoichiometries of the type Cu(OAc)2(B)n(B=L-L or L-LHCl and n=2, 1 or 0.5). 相似文献
4.
Narinder Singh 《Tetrahedron》2004,60(25):5393-5405
New podands based on the p-tert-butylcalix[4]arene unit with substitution at the lower rim incorporating imine units, have been synthesized in high yield by simple condensation method. These podands have been shown to extract and transport Ag+ selectively over alkali, alkaline earth metal cations, Zn2+, Pb2+ and Hg2+ ions, from neutral aqueous phase to organic phase. In all the ligands the calix unit has been found to be present in a cone conformation except for the one having pyridine as end group, at the ortho position. It has been isolated in two conformations; cone and 1,2-alternate. To the best of our knowledge, this may be the first 1,3-lower rim substituted calix[4]arene to exist in a 1,2-alternate conformation and is among a few known compounds with this conformation in the general class of calix[4]arenes. A complex of this ligand, which happens to be the highest extractant of Ag+ has been isolated and characterized using mass, 1H and 13C NMR spectroscopy's and elemental analysis. The spectroscopic evidence and molecular modelling studies performed on the complex suggest a participation of the imine and pyridine nitrogens and two of the ether oxygens in coordination to the metal ion. The X-ray crystal structures of three of the ligands establish the formation of inclusion complexes with polar acetonitrile solvent molecules. The 1H and 13C NMR spectra of all the compounds, taken in CDCl3, show the presence of acetonitrile molecules in the cavity of the calix[4]arene, indicating inclusion of the neutral guest molecules in the solution phase as well. For one of the podands X-ray crystal structure has shown a formation of clatharate complex of chloroform with the ligand which has rarely been found in the case of calix[4]arenes. 相似文献
5.
6.
Narinder Sing S. B. Mathur 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2-3):169-175
Abstract Anode slimes obtained from the electrolytic refining of copper contain selenium and tellurium in the form of selenides and tellurides of metals, e.g., copper and silver. The slimes were treated with sulfur under vacuum; selenides and tellurides decomposed to give selenium and tellurium in metallic form which condensed on a cooler zone. Various parameters studied were temperature, time, sulfur addition, briquetting pressure, and fineness of sulfur added. The X-ray diffraction studies carried out on treated and then on untreated slime proved the reaction of sulfur with selenide and telluride of copper to give copper sulfide, selenium, and tellurium. Sulfurization at around 475°C for 60 min gives optimum recoveries. 相似文献
7.
8.
Narinder Singh 《Supramolecular chemistry》2013,25(5):351-357
A series of new p-tert-butylcalix[4]arene-based dipodal receptors are synthesised in high yields. The calix[4]arene units of all the receptors have been found to be present in cone conformation. To optimise the good extraction ability and high transport rate, we synthesised the receptors that differ from each other in their end groups. These receptors extract Cu2+ ion selectively from the buffered aqueous medium containing a mixture of metal ions. The receptor bearing four sp3 nitrogens has by far the greater ability to extract Cu2+ than the other receptors. All these receptors were effectively used for Cu2+ ion transport from the aqueous buffered source phase to the aqueous receiving phase. 相似文献
9.
Dr. Anil Kuwar Rahul Patil Amanpreet Singh Prof. Ratnamala Bendre Dr. Narinder Singh 《Chemphyschem》2014,15(18):3933-3937
A new disulfide‐based, imine‐linked fluorescent receptor 1 was processed into organic nanoparticles (ONPs) with an average particle size of 79 nm. The photophysical properties of the ONPs were evaluated by UV/Vis absorption spectroscopy. Receptor 1 selectively recognized Co2+ ions in water with a detection limit down to 88 nm. 相似文献
10.
For general inferential families with a mixture of one- and two-sided inferences two procedures are proposed to compare several treatments with a control under heteroscedasticity. Critical constants required for the proposed procedures are tabulated, and a numerical example is given. 相似文献