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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Structure and Stability of Pentafluoroaniline and 4-Aminononafluorobiphenyl Radical Anions: Optically Detected Electron Paramagnetic Resonance, Time-Resolved Fluorescence, Time-Resolved Magnetic Field Effect, and Quantum Chemical Study
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Structure and Stability of Pentafluoroaniline and 4-Aminononafluorobiphenyl Radical Anions: Optically Detected Electron Paramagnetic Resonance, Time-Resolved Fluorescence, Time-Resolved Magnetic Field Effect, and Quantum Chemical Study

机译：五氟苯胺和4-氨基氟联苯自由基阴离子的结构和稳定性：光学检测电子顺磁共振，时间分辨荧光，时间分辨磁场效应和量子化学研究

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Radical anions (RAs) are the key intermediates of the selective hydrodefluorination of polyfluoroarenes. We used the techniques of optically detected electron paramagnetic resonance (OD EPR), time-resolved fluorescence, time-resolved magnetic field effect (TR MFE), and the density functional theory to study the possibility of RAs formation from 4-aminononafluorobiphenyl (1) and pentafluoroaniline (2) and estimate their lifetimes and decay channels. To our knowledge, both RAs have not been detected earlier. We have registered the OD EPR spectrum for relatively stable in nonpolar solutions 1(-center dot) but failed to register the spectra for 2(-). However, we have managed to fix the 2(-) by the TR MFE method and obtained its hyperfine coupling constants. The lifetime of 2(-) was found to be only a few nanoseconds. The activation energy of its decay was estimated to be 3.6 +/- 0.3 kcal/mol. According to the calculation results, the short lifetime of 2(-center dot) is due to the RA fast fragmentation with the F elimination from ortho-position to the amine group. The calculated energy barrier, 3.2 kcal/mol, is close to the experimental value. The fragmentation of 2(-center dot) in a nonpolar solvent is possible due to the stabilization of the incipient F- anion by the binding with the amine group proton.
机译：自由基阴离子（RAs）是多氟芳烃选择性加氢脱氟的关键中间体。我们使用光学检测的电子顺磁共振（OD EPR），时间分辨的荧光，时间分辨的磁场效应（TR MFE）和密度泛函理论的技术来研究由4-氨基九氟联苯形成RA的可能性（1）和五氟苯胺（2）并估算其寿命和衰变通道。据我们所知，两个RA都没有更早被发现。我们已经注册了OD EPR光谱，以便在非极性溶液1（-中心点）中相对稳定，但未能注册2（-）的光谱。但是，我们设法通过TR MFE方法固定了2（-），并获得了其超精细耦合常数。发现2（-）的寿命只有几纳秒。其衰变的活化能估计为3.6 +/- 0.3kcal / mol。根据计算结果，2（-中心点）的短寿命是由于RA快速断裂和F从邻位到胺基的消除。计算得出的能垒为3.2 kcal / mol，接近实验值。非极性溶剂中2（中心点）的断裂是可能的，这是由于初始F-阴离子通过与胺基质子的结合而稳定的缘故。

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