Center for Self-Assembly and Complexity, Institute for Basic Science (IBS) , Pohang 790-784, Republic of Korea.
Department of Chemistry, Pohang University of Science and Technology , Pohang 790-784, Republic of Korea.
J Am Chem Soc. 2017 Nov 1;139(43):15300-15303. doi: 10.1021/jacs.7b08753. Epub 2017 Oct 19.
Notwithstanding the notable progress in the synthesis of N-heterocyclic carbene-stabilized radicals, aminyl radicals, supported by NHCs or otherwise, have been scarcely studied due to synthetic challenges. Triazenyl radical is a particular form of aminyl radical that contains three adjacent nitrogen atoms, and offers intriguing possibilities for unique reactivity and physical properties stemming from expected delocalization of the spin density over the NNN moiety and its conjugated substituents. Here, we report the synthesis and full characterization of the first NHC-stabilized triazenyl radicals, obtained by one-electron reduction of the corresponding triazenyl cations with potassium metal. These radicals reversibly oxidize back to the cations upon treatment with transition metal sources or electrophiles, and abstract H atom from xanthene to form a new N-H bond at the center nitrogen atom. Potential application of the redox couple between triazenyl cation and triazenyl radical was demonstrated as cathode active materials in lithium ion batteries.
尽管在合成 N-杂环卡宾稳定的自由基方面取得了显著进展，但由于合成上的挑战，氨基自由基，由 NHC 或其他方式支持的氨基自由基，研究甚少。三嗪基自由基是一种特殊形式的氨基自由基，它含有三个相邻的氮原子，并提供了有趣的可能性，因为预计自旋密度在 NNN 部分及其共轭取代基上的离域化，从而具有独特的反应性和物理性质。在这里，我们报告了首例 NHC 稳定的三嗪基自由基的合成和全谱表征，通过用钾金属还原相应的三嗪阳离子获得。这些自由基在与过渡金属源或亲电试剂处理时可逆地氧化回阳离子，并从香豆素中提取 H 原子，在中心氮原子上形成新的 N-H 键。三嗪阳离子和三嗪自由基之间的氧化还原偶对作为锂离子电池的阴极活性材料的潜在应用得到了证明。
