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. F6 -[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 (ArH -ArF ) hetero-stacking to ArH -ArH /ArF -ArF 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 ArH -ArF stacking motif is not always applicable to Fn -[4]helicenes with twisted π-surfaces.

中文翻译：

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部分氟化[4] Helicenes的柱状堆叠：CH⋅⋅⋅F相互作用改变堆叠方向。

多环芳烃的部分氟化通常会产生层状晶体堆积，其中氟化芳族表面堆叠在非氟化芳族表面上。在本文中，我们报道了由峡湾区域的H和F原子引起的部分氟化[4]螺旋烯的合成和晶体堆积，以及空间拥挤。F6- [4]螺线烯形成由全氟和非氟萘部分的交替排列组成的头尾尾圆柱状堆叠。随着氟含量的降低，借助于在峡湾区域的分子间CH⋅⋅⋅F接触，芳族堆积从芳烃-氟亚芳基（ArH -ArF）异质堆积转变为ArH -ArH / ArF -ArF均匀堆积。结果，出现了头对头的柱状堆叠。因此，