Isolable Zwitterionic Pyridinio-semiquinone π-Radicals. Mild and Efficient Single-Step Access to Stable Radicals

A rational design based on the proton-coupled electron transfer (PCET) concept allows us to structurally characterize for the first time isolable, air- and moisture-stable semiquinone radicals in a zwitterionic neutral form. The presence of an alkoxy and the bulky pyridinio substituents causes only a minor perturbation of either the redox potentials or the spectral UV−vis characteristics of the semiquinone core but significantly stabilizes the new radicals.

基于质子耦合电子转移（proton-coupled electron transfer, PCET）概念开展的理性设计，使我们首次在结构上表征了可分离、耐空气且抗潮湿的两性离子中性形式半醌自由基。烷氧基与大位阻吡啶鎓取代基的存在，仅对半醌核心的氧化还原电位及紫外-可见（UV-vis）光谱特性造成微弱扰动，却能显著稳定这类新型自由基。