Chen Chao, Ruan Huapeng, Feng Zhongtao, Fang Yong, Tang Shuxuan, Zhao Yue, Tan Gengwen, Su Yuanting, Wang Xinping
State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, P. R. China.
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China.
Angew Chem Int Ed Engl. 2020 Jul 13;59(29):11794-11799. doi: 10.1002/anie.202001842. Epub 2020 May 18.
Although diradicals and azaacenes have been greatly attractive in fundamental chemistry and functional materials, the isolable diradical dianions of azaacenes are still unknown. Herein, we describe the first isolation of pyrene-fused azaacene diradical dianion salts [(18-c-6)K(THF) ] [(18-c-6)K] ⋅1 and [(18-c-6)K(THF)] ⋅2 by reduction of the neutral pyrene-fused azaacene derivatives 1 and 2 with excess potassium graphite in THF in the presence of 18-crown-6. Their electronic structures were investigated by various experiments, in conjunction with theoretical calculations. It was found that both dianions are open-shell singlets in the ground state and their triplet states are thermally readily accessible owing to the small singlet-triplet energy gap. This work provides the first examples of crystalline diradical dianions of azaacenes with considerable diradical character.
尽管双自由基和氮杂并苯在基础化学和功能材料领域极具吸引力，但氮杂并苯的可分离双自由基二价阴离子仍然未知。在此，我们描述了通过在18-冠-6存在下，用过量的钾石墨在四氢呋喃中还原中性的芘稠合氮杂并苯衍生物1和2，首次分离出芘稠合氮杂并苯双自由基二价阴离子盐[(18-c-6)K(THF) ] [(18-c-6)K] ⋅1和[(18-c-6)K(THF)] ⋅2。通过各种实验并结合理论计算对它们的电子结构进行了研究。结果发现，这两种二价阴离子在基态都是开壳单线态，由于单线态-三线态能隙小，它们的三线态在热激发下很容易达到。这项工作提供了具有相当双自由基特征的氮杂并苯晶体双自由基二价阴离子的首个实例。
