Suzuki Risa, Uziie Yuto, Fujiwara Wataru, Katagiri Hiroshi, Murase Takashi
Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata, Yamagata, 990-8560, Japan.
Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata, 992-8510, Japan.
Chem Asian J. 2020 Apr 17;15(8):1330-1338. doi: 10.1002/asia.202000037. Epub 2020 Mar 19.
The partial fluorination of polycyclic aromatic hydrocarbons often produces a layered crystal packing, where fluorinated aromatic surfaces are stacked over nonfluorinated aromatic surfaces. Herein, we report the synthesis and crystal packing of partially fluorinated [4]helicenes with steric congestion resulting from H and F atoms in the fjord region. F -[4]Helicene forms head-to-tail columnar stacks consisting of an alternate arrangement of perfluorinated and nonfluorinated naphthalene moieties. With decreasing fluorine content, aromatic stacking switched from arene-fluoroarene (Ar -Ar ) hetero-stacking to Ar -Ar /Ar -Ar homo-stacking with the help of intermolecular C-H⋅⋅⋅F contacts in the fjord region. As a result, head-to-head columnar stacks appear. Therefore, the conventional Ar -Ar stacking motif is not always applicable to F -[4]helicenes with twisted π-surfaces.
多环芳烃的部分氟化通常会产生层状晶体堆积，其中氟化芳香表面堆叠在非氟化芳香表面之上。在此，我们报道了在峡湾区域因氢原子和氟原子导致空间拥挤的部分氟化[4]螺旋烯的合成及晶体堆积。F-[4]螺旋烯形成头对尾柱状堆积，由全氟萘基和非氟萘基交替排列组成。随着氟含量的降低，在峡湾区域分子间C-H⋅⋅⋅F接触的帮助下，芳香堆积从芳烃-氟芳烃（Ar -Ar ）异质堆积转变为Ar -Ar /Ar -Ar 同质堆积。结果，出现了头对头柱状堆积。因此，传统的Ar -Ar 堆积模式并不总是适用于具有扭曲π表面的F-[4]螺旋烯。
