• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Radical Anions of Mono- and Bis-fulleropyrrolidines: An EPR Study
【24h】

Radical Anions of Mono- and Bis-fulleropyrrolidines: An EPR Study

机译：单和双全吡咯烷酮的自由基阴离子：EPR研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The radical anions of three C_(60) derivatives (N-methyl-3,4-fulleropyrrolidine, N-methyl-2-(3,6,9-trioxadecyl)-3,4-fulleropyrrolidine, and bis-N-methyl-3,4-fulleropyrrolidine are respectively MFP~-, tgeMFP~-, and bisMFP~-) have been investigated by continuous wave (cw) and pulsed EPR in methyltetrahydrofuran and tetrahydrofuran solutions. The EPR spectra for MFP~- and tegMFP~- show a 1:1:1 triplet, due to the hyperfine coupling with the pyrrolidine nitrogen. The EPR spectrum of bisMFP~- shows a superimposition of two signals, each due to a 1:2:3:2:1 quintet. Each quintet is due to the hyperfine coupling with the two pyrrolidine nitrogen atoms. The two signals are attributed to two different conformers of the radical. A direct transfer of spin density from the C_(60)~- sphere to the nitrogen atoms is discussed as arising from the bent conformation of the pyrrolidine rings. All the spectra show several weaker satellite lines, due to the radical anions containing a ~(13)C atom. From their analysis a C_(2v) symmetry for the spin distribution is obtained in the case of MFP~- and tegMFP~-. The EPR line widths of these latter radicals at room temperature are larger than those expected on the basis of spin relaxation due to rotational diffusion in solution, and the line widths decrease upon decreasing the temperature. Pulsed EPR measurements of T_1 in liquid and frozen solutions show that the EPR line widths are determined by the anomalously short lifetimes of the spin states. The temperature dependence of T_1 obeys to the Arrhenius law, giving an activation energy of 7 kJ/mol. The latter results are compared with those obtained in the past for the lone C_(60)~-. They are attributed to the closeness of the electronic levels, due to the weak perturbation of the pyrrolidine ring on the symmetrical electronic distribution of C_(60). On the other hand, the spin relaxation properties of bisMFP~- are shown those expected for a nonsymmetrical radical. The comparison of cw- and pulsed-EPR spectra of MFP~- in frozen solutions of MeTHF and THF indicates the presence of aggregates of interacting radicals in THF.
机译：三种C_（60）衍生物的自由基阴离子（N-甲基-3,4-全吡咯烷，N-甲基-2-（3,6,9-三氧十六烷基）-3,4-全吡咯烷和双-N-甲基-通过连续波（cw）和脉冲EPR法在甲基四氢呋喃和四氢呋喃溶液中研究了3,4-全氟吡咯烷分别是MFP-，tgeMFP-和bisMFP-。 MFP-和tegMFP-的EPR谱显示出1：1：1的三重态，这是由于与吡咯烷氮的超精细偶合。 bisMFP〜-的EPR频谱显示两个信号的叠加，每个信号归因于1：2：3：2：1五重奏。每个五重奏是由于与两个吡咯烷氮原子的超精细偶合。这两个信号归因于基团的两个不同构象体。讨论了自旋密度从C_（60）〜-球到氮原子的直接转移，是由于吡咯烷环的弯曲构象引起的。由于包含〜（13）C原子的自由基阴离子，所有光谱均显示出几条较弱的卫星谱线。根据他们的分析，在MFP〜-和tegMFP〜-的情况下，获得了自旋分布的C_（2v）对称性。由于在溶液中的旋转扩散，在室温下这些自由基的EPR线宽大于基于自旋弛豫所预期的EPR线宽，并且随着温度降低，线宽减小。液体和冷冻溶液中T_1的脉冲EPR测量表明，EPR线宽由旋转状态的异常短寿命决定。 T_1的温度依从性符合阿伦尼乌斯定律，活化能为7 kJ / mol。将后者的结果与过去针对单独的C_（60）〜-获得的结果进行比较。它们归因于电子能级的紧密性，这是由于吡咯烷环在C_（60）的对称电子分布上的微弱扰动。另一方面，显示了bisMFP-的自旋弛豫特性，这些是非对称自由基所期望的。在MeTHF和THF的冷冻溶液中MFP〜-的cw-和脉冲EPR光谱的比较表明，在THF中存在相互作用的自由基的聚集体。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号