Zhou Zheng, Fu Lin, Hu Yunbin, Wang Xiao-Ye, Wei Zheng, Narita Akimutsu, Müllen Klaus, Petrukhina Marina A
Department of Chemistry, University at Albany, State University of New York, 1400 Washington Ave, Albany, NY, 12222, USA.
State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Weijin Road 94, Tianjin, 300071, China.
Angew Chem Int Ed Engl. 2020 Sep 7;59(37):15923-15927. doi: 10.1002/anie.202005852. Epub 2020 Jul 15.
Chemical reduction of a benzo-fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of 1. The doubly-reduced helicene 1 has been characterized by single-crystal X-ray diffraction as a solvent-separated ion triplet with two potassium counterions. The triply- and tetra-reduced helicenes, 1 and 1 , have been crystallized together in an equimolar ratio and both form the contact-ion complexes with two Rb ions each, leaving three remaining Rb ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of 1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in 1 vs. 2.09 Å in 1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in 1 to 20.7° in 1 . Theoretical calculations provided the pattern of negative charge build-up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X-ray crystallographic and NMR spectroscopic data.
用两种碱金属钾和铷对苯并稠合双[7]螺旋烯（1）进行化学还原，可得到1的三种不同还原态。双还原螺旋烯1已通过单晶X射线衍射表征为具有两个钾抗衡离子的溶剂分隔离子三重态。三还原和四还原螺旋烯1和1已以等摩尔比一起结晶，并且两者都形成与两个铷离子的接触离子络合物，剩下的三个铷离子被冠醚和四氢呋喃分子包裹。作为1逐步还原的结构结果，螺旋烯的中心轴在电子添加时变得更加压缩（1中的1.42 Å与1中的2.09 Å相比）。这伴随着额外的核心扭曲，因为外围二面角从1中的16.5°增加到1中的20.7°。理论计算给出了每次电子添加后扭曲螺旋烯骨架上负电荷积累和分布的模式，结果与X射线晶体学和核磁共振光谱数据一致。
