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Columnar Stacking of Partially Fluorinated [4]Helicenes: C−H⋅⋅⋅F Interactions Change the Stacking Orientation
Author(s) -
Suzuki Risa,
Uziie Yuto,
Fujiwara Wataru,
Katagiri Hiroshi,
Murase Takashi
Publication year - 2020
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.202000037
Subject(s) - stacking , helicene , crystallography , aromaticity , intermolecular force , steric effects , chemistry , fluorine , crystal structure , crystal (programming language) , stereochemistry , materials science , organic chemistry , molecule , computer science , programming language
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 6 ‐[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 H −Ar F ) hetero‐stacking to Ar H −Ar H /Ar F −Ar F 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 H −Ar F stacking motif is not always applicable to F n ‐[4]helicenes with twisted π‐surfaces.