Conformational Change with Steric Interactions Affects the Inner Sphere Component of Concerted Proton–Electron Transfer in a Pyridyl-Appended Radical Cation System
作者:Evan A. Welker、Brittney L. Tiley、Crina M. Sasaran、Matthew A. Zuchero、Wing-Sze Tong、Melissa J. Vettleson、Robert A. Richards、Jonathan J. Geruntho、Stefan Stoll、Jeffrey P. Wolbach、Ian J. Rhile
DOI:10.1021/acs.joc.5b01427
日期:2015.9.4
surface while maintaining the hydrogen bond; in contrast, MPTP•+ + tBu3PhOH maintains its conformation throughout the reaction. This difference is reflected in both experiment and calculations with ΔGMPTP•+⧧ < ΔGPPT•+⧧ despite ΔGMPTP•+° > ΔGPPT•+°. Experimental results with 2,6-di-tert-butyl-4-methoxyphenol are similar. Hence, despite the structural similarity between the compounds, differences in the inner
质子耦合电子转移(PCET)模型系统将单电子氧化剂和碱结合起来产生净氢原子受体。我们生成了两种持久的吡啶基附加自由基阳离子:10-(pyrid-2-yl)-10 H -phenothiazinium ( PPT •+ ) 和 3-(pyrid-2-yl)-10-methyl-10 H -phenothiazinium ( MPTP •+ )。 EPR 谱和相应的计算表明吩噻嗪自由基阳离子在吡啶氮上具有最小的自旋。添加受阻酚会导致自由基阳离子衰变,并形成质子化产物和相应的苯氧基自由基。中间体形成的 Δ G ° 值(通过循环伏安法和 p Ka测量确定)排除了逐步机制,并且动力学同位素效应支持协同质子电子转移(CPET)作为机制。计算表明, PPT •+ + t Bu 3 PhOH 的反应在保持氢键的同时,发生了显着的构象变化,非绝热表面存在空间相互作用。相比之下, MPTP •+ + t Bu