排序方式: 共有29条查询结果,搜索用时 46 毫秒
1.
Four novel copper(Ⅱ) complexes have been synthesized,namely Cu(hfac)2NITPhNO2 (1),Cu(hfac)2NITPhCH3 (2),Cu(pfpr)2NITPhNO2,(3) and Cu(Pfpr)2NITPhCH3 (4),where hfac= hexafluoro-acetylacetonate,pfpr=pentafluoropropionate,NITR.=2-R-4,4,5,5-tetraniethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide.(R=4-nitrophenyl,4-methylphenyl).These complexes were rharicter-ized by elemental analyses,IR,electronic spectra and molar conductance.The temperature-dependent magnetic susceptibility of complexes 1 and 3 have been studied in the 4 300 K range,giving I he exchange integral J=10.56 cm-1 for complex 1 and J =-30.9 cm-1 for complex 3. 相似文献
2.
ESR波谱和流动-停止UV动力学研究表明,水溶液中2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基1和相应氧铵澳盐2均可将N,N,N′,N′-四甲基对苯二胺(TMPD)氧化为相应自由基正离子TMPD+,2还能将TMPD+进一步氧化为二价正离子TMPD~(2+).TMPD+可发生可逆歧化,其稳定性强烈受介质酸碱性的影响。利用计算机对动力学曲线的模拟测得上述有关反应的速率常数,并讨论了反应机理。 相似文献
3.
The interaction of molecular oxygen with derivatives of nitroxide EPR spin labels has been investigated using nuclear spin-relaxation spectroscopy in aqueous and nonaqueous solvents. The proton spin-lattice relaxation rate induced by oxygen provides a measure of the local concentration of oxygen, which we find is dependent on solvent. In water, the hydrophobic effect increases the local concentration of oxygen in the nonpolar portions of solute molecules. For nitroxides reduced to the hydroxylamine in aqueous solutions, we find that the local concentration of oxygen is approximately twice that associated with a free diffusion hard sphere limit, while in octane, this effect is absent. These results show that nitroxide based ESR oximetry may suffer a reference concentration shift of order a factor of two if the aqueous nitroxide spectrum or relaxation is used as the reference. 相似文献
4.
Sergei F. Vasilevsky Svetlana V. Klyatskaya Dmitri V. Stass Igor A. Grigir’ev José Elguero 《Tetrahedron letters》2004,45(41):7741-7743
The Stephens-Castro reaction of copper(I) salts of 1-aryl(hetaryl)alkynes with 2,2,5,5-tetramethyl-4-[2-(4-iodophenyl)-vinyl]imidazoline-3-oxide-1-ol proved to be a general method for the preparation of 2,2,5,5-tetramethyl-4-[2-(p-aryl(hetaryl)ethynylphenyl)]vinyl-3-imidazoline-3-oxide-1-oxyles. 相似文献
5.
A combined electron spin resonance (ESR) and density functional theory study has been carried out to obtain deeper insight in the reaction mechanism of the photorearrangement of 3‐hydroxyindolic nitrones. Also, in this case, the combination of these techniques constitutes a powerful tool when discriminating between different reaction pathways. In particular, density functional theory calculations played an important role for unraveling the overlapping of signals coming from different species in the ESR spin trapping experiments. In the present study, the computed energies and the corresponding ESR parameters of each possible isomer hypothesized have been considered, taking also into account their different possibilities of intramolecular H‐bond formation. However, the results obtained indicate that the possibility of intramolecular H‐bonding did not play a determinant role in this case. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
6.
Elisabetta Mezzina Paola Franchi Marco Lucarini 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):179-183
A new synthetic strategy for the preparation of persistent paramagnetic cyclodextrin-based rotaxanes is described. The method
consists in the formation of inclusion complexes between α-cyclodextrin (α-CD) and α,ω-dithiols containing an octamethylene
chain covalently trapped by bulky stoppers composed of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) radical fragments. Interaction
of α-CD (the bead) and 1,8-octanedithiol (the thread) occurs in aqueous alkaline media and encapsulation is obtained by nucleophilic
substitution at both termini of the linear component with a bulky paramagnetic iodide [2,2,6,6-tetramethyl-4-(2-iodoacetamide)piperidine-N-oxyl].
Structure determination of the new [2]rotaxane by 1H NMR is reported and the spectroscopic data are discussed. 相似文献
7.
Jerzy Zakrzewski Jarosław Hupko Krzysztof Kryczka 《Monatshefte für Chemie / Chemical Monthly》2003,134(6):843-850
Summary. The reaction of thiophosgene with 2,2,6,6-tetramethylpiperidine-1-oxyl (used as a model nitroxyl radical) was examined. 2,2,6,6-Tetramethylpiperidine
and 2,2,6,6-tetramethyl-1-hydroxypiperidine were identified as products. The reaction is not competitive with the reaction
of thiophosgene with an amino group. Thus, three nitroxides with an isothiocyanate group were synthesized from thiophosgene
and the nitroxides containing the amino substituent.
Corresponding author. E-mail: zakrzewski@ipo.waw.pl
Received July 22, 2002; accepted (revised) September 3, 2002
Published online March 13, 2003 相似文献
8.
New, dual profluorescent spin-probes and their fluorescent amine analogues, as potential spin traps, have been synthesized and characterized. Comparison between the fluorescence spectra of amines and their corresponding nitroxides established spacer distance dependent quenching of fluorescence. 相似文献
9.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1295-1303
ABSTRACT Stabilized nitroxide radicals (TEMPO and its 4-hydroxy- and 4-oxo-derivatives) have been examined as inhibitors of the radical polymerization at 60°C of methyl methacrylate using azobisisobutyronitrile as initiator. Inhibition periods have been recorded and also the rates of the subsequent polymerizations and the molecular weights of the resulting polymers. It is concluded that alkoxyamines, formed during the inhibition, affect the polymerizations and lead to lowering of the molecular weights of the resulting polymers. The effect is attributed to a radical-displacement process involving the alkoxyamine and a growing polymer radical. 相似文献
10.
New, paramagnetic unnatural α-amino acids were synthesized by the O'Donnell method. In the new amino acids nitroxide is condensed with thiophene, benzene, and tetrahydroisoquinoline ring, or linked through a methylene, benzyl or propargyl spacer. Some of the racemic paramagnetic α-amino acid esters described earlier or in this work were resolved by fractional crystallization of diastereomeric salts. Another approach for optically active paramagnetic amino acids is the modification of S-tyrosine derivatives with Pd-catalyzed cross-coupling reactions with paramagnetic acetylene and with a paramagnetic boronic acid. 相似文献