Fang Yong, Zhang Li, Cheng Cheng, Zhao Yue, Abe Manabu, Tan Gengwen, Wang Xinping
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, P. R. China.
Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Japan.
Chemistry. 2018 Mar 2;24(13):3156-3160. doi: 10.1002/chem.201706060. Epub 2018 Feb 5.
One-electron reductions of MesAs=Fl (1; Fl*=2,7-di-tert-butylfluorenylidene, Mes*=2,4,6-tBu C H ) and diarsaalkenes [1,2-b]-IF(=AsMes*) (2; IF=indenofluorene) with potassium led to the isolation of the arsenic-centered radical anion salts 1K and 2K, respectively. The diradical dianion salts 2K and 3K were afforded by the reduction of 2 and 2,8-tBu -[2,1-b]-IF(=AsMes*) (3) with an excess amount of KC . The radicals have been investigated by single-crystal X-ray crystallography, EPR, and UV/Vis absorption spectroscopy, along with theoretical calculations. The calculations revealed that 2K and 3K feature open-shell singlet ground states with singlet-triplet energy gaps of 2.1 and 1.0 kcal mol , respectively. They are readily thermally excited to triplet states as demonstrated by EPR spectroscopy. The obtained diradicals represent the first examples of heavier Group 15 element centered diradicals with experimentally observable triplet states.
用钾对MesAs=Fl（1；Fl* = 2,7 - 二叔丁基芴叉基，Mes* = 2,4,6 - tBu₃C₆H₂）和二砷烯烃[1,2 - b] - IF(=AsMes*)（2；IF = 茚并芴）进行单电子还原，分别得到了以砷为中心的自由基阴离子盐1K和2K。通过用过量的KC₈还原2和2,8 - tBu₂ - [2,1 - b] - IF(=AsMes*)（3）得到了双自由基二阴离子盐2K和3K。通过单晶X射线晶体学、电子顺磁共振（EPR）和紫外/可见吸收光谱以及理论计算对这些自由基进行了研究。计算结果表明，2K和3K具有开壳层单重态基态，单重态 - 三重态能隙分别为2.1和1.0 kcal mol⁻¹。如EPR光谱所示，它们很容易被热激发到三重态。所得到的双自由基代表了具有实验可观测三重态的第15族较重元素中心双自由基的首个实例。
