共查询到18条相似文献,搜索用时 78 毫秒
1.
氮氧自由基调控聚合(NMP)是制备微观结构可控(如窄分子量分布)的聚合物材料最主要的技术手段之一。在过去的二十年间,NMP取得了相当大的成就,实现了MMA、n-BA、丙烯酰胺,二烯烃和丙烯腈等多种单体的可控/"活性"聚合,分子量分布达到1.1以下,同时利用NMP制备了具有既定结构的聚合物,如嵌段聚合物、接枝聚合物、星形聚合物和梳形聚合物等。而与光聚合技术的结合,使NMP聚合取得了更大的突破,实现了室温下的光可控/"活性"聚合,且大大提升了聚合反应速率。近年来光引发氮氧自由基调控聚合的研究进展主要集中在光敏化技术方面,包括分子内敏化和分子间敏化,本文对其各自的敏化机理和研究成果进行总结和评述,希望有助于国内读者了解这方面研究工作的状况,促进国内相关研究工作的发展。 相似文献
2.
介绍了含氮氧自由基磁偶合体系及金属-自由基类分子铁磁体的结构特点及其磁偶合机制.对其发展趋势和前景作一展望. 相似文献
3.
传统甾醇中间体氧化采用重金属铬作为氧化剂,存在毒性大和环境污染等问题。电催化氧化(ECO)以其高效、环保、可控的优点备受青睐,被认为是一种可替代传统工艺的方法。然而,目前ECO面临低电流密度和低时空产率的挑战。本研究采用一步溶剂热法在石墨毡上制备自支撑NiFe-MOF纳米片电催化剂,并耦合NiFe-MOF与氮氧自由基(4-乙酰氨-2,2,6,6-四甲基哌啶-1-氧)协同电催化策略以提高ECO性能。研究发现碱性电解液可重构NiFe-MOF催化剂,从而提高催化活性。此外,连续流动强化传质,成功实现以1 00 mA·cm-2的大电流密度对19-羟基-4-雄甾烯-3,17-二酮(1a)的选择性电催化氧化,且选择性高达98%,时空产率可达1 5.88 kg·m-3·h-1,是间歇电反应器的35倍。寿命测试发现经10次循环反应后,NiFe-MOF/ACT协同体系对ECO仍具有较高的转化率。通过增大NiFe-MOF面积,将其组装至连续流动式电反应器并进行ECO恒电流电解,可达到12.99 kg·m-3·h 相似文献
4.
5.
本文报道将先前合成的双多氟和全氟烷基氮氧自由基1与多氟和合氟亚硝基烷烃2混合溶液的技术应用于烷烃、芳烃3自由基攫氢反应的研究,氮氧自由基1由烷烃,芳烃迅速攫氢转变为羟胺,生成的烷基自由基中间体立即被2截捕得到稳定的自旋加合物4和5.由自施加合物ESR参数,可以确定自由基结构并由引来研究攫氢反应机理,本文也提供了一个产生大量含氟烷基氮氧自由基并研究其结构的有效而简单的方法。 相似文献
6.
氮氧自由基-金属配合物的合成和功能性研究,已成为分子磁性材料的一个热点课题。本文主要介绍了近年来氮氧自由基-金属配合物型分子基磁体、单分子磁体、单链磁体、分子自旋转换配合物等的最新研究成果,并就这一领域的发展前景做一展望。 相似文献
7.
8.
9.
10.
11.
Marek Burian Ladislav Omelka Silvie Ondrášová Vlasta Brezová 《Monatshefte für Chemie / Chemical Monthly》2003,134(4):501-508
Summary. Several N-phenyl substituted 1,4- and 1,2-phenylenediamines were oxidized using radicals and 3-chloroperbenzoic acid. EPR spectroscopy confirmed the generation of nitroxide radicals originating from the
oxidation of the bridging -NH-group. No radical products suggesting the simultaneous reaction with the NH2-group were observed. Only in the case of 1,4-phenylenediamine, a low concentration of nitroxide radical H–NO–C6H4–NH2 was obtained. In o-aminodiphenylnitroxide the steric effect of the NH2-group causes a partially asymmetrical spin density distribution in both phenyl rings.
Corresponding author. E-mail: omelka@fch.vutbr.cz
Received September 30, 2002; accepted October 4, 2002 相似文献
12.
The synthesis, crystal structure and magnetic properties of the non-transition metals; Cd(II), Zn(II), Hg(II), Mg(II) and the transition metals; Co(II), Ni(II), Cu(II) complexes with 2-(4-pyridyl)-4,4,5,5-tetra-methylimidazolinyl-l-oxy-3-oxide (NITpPy) are presented. The compounds of free radical NITpPy, HgCl2(NITpPy), and Zn(acac)2(NITpPy) crystallize in the same monoclinic system of space group C2/c. The magnetic properties of the temperature-dependent magnetic susceptibility of NITpPy and its metal complexes are discussed according to the Heisenberg model. A weak ferromagnetic coupling in NITpPy and a weak antiferromagnetic coupling in the metal complexes have been revealed. 相似文献
13.
14.
15.
Tobias Hilche Dr. Philip H. Reinsberg Dr. Sven Klare Dr. Theresa Liedtke Luise Schäfer Prof. Dr. Andreas Gansäuer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(15):4903-4912
The combination of synthesis, rotating ring-disk electrode (RRDE) and cyclic voltammetry (CV) measurements, and computational investigations with the aid of DFT methods shows how a thiourea, a squaramide, and a bissulfonamide as additives affect the EqCr equilibrium of Cp2TiCl2. We have, for the first time, provided quantitative data for the EqCr equilibrium and have determined the stoichiometry of adduct formation of [Cp2Ti(III)Cl2]−, [Cp2Ti(III)Cl] and [Cp2Ti(IV)Cl2] and the additives. By studying the structures of the complexes formed by DFT methods, we have established the Gibbs energies and enthalpies of complex formation as well as the adduct structures. The results not only demonstrate the correctness of our use of the EqCr equilibrium as predictor for sustainable catalysis. They are also a design platform for the development of novel additives in particular for enantioselective catalysis. 相似文献
16.
17.
18.
This work presents an experimental and theoretical study to address the chemical reactivity of series of nitroxide radicals. For that purpose two physicochemical properties: the half-wave potential and the hyperfine coupling constants of the nitrogen nuclei, were analyzed. Experimental values are compared with electronic structure calculations at the BHandHLYP/6-311++G(2d,2p) level. E1/2 values were in good agreement with the adiabatic ionization potential when including the solvent effects by the Cramer and Truhlar Solvation Model. Preeliminar experimental electron spin deslocalization studies suggest that structural hindrance plays an important role in their deslocatization mechanism. 相似文献