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Construction of Helical Structures with Multiple Fused Anthracenes: Structures and Properties of Long Expanded Helicenes
Author(s) -
Fujise Kei,
Tsurumaki Eiji,
Wakamatsu Kan,
Toyota Shinji
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202004720
Subject(s) - anthracene , stacking , excited state , molecular orbital , excimer , photochemistry , chemistry , fluorescence , crystallography , chromophore , absorption spectroscopy , molecule , stereochemistry , organic chemistry , optics , physics , nuclear physics
Polycyclic aromatic compounds consisting of four or five fused anthracene units were synthesized by PtCl 2 ‐catalyzed cycloisomerization as novel long expanded helicenes. These compounds have helical structures with significant stacking of the terminal anthracene moieties at 0.33 nm interlayer distance. In the UV‐vis and fluorescence spectra, the absorption and emission bands were red‐shifted as the number of fused anthracene units was increased. The characteristic broad and long‐lived emission bands of the long analogues are explained by the excimer‐like stabilization of the excited state. These photophysical data as well as their cyclic voltammetric data are discussed on the basis of the π‐conjugation and interlayer π⋅⋅⋅π interactions in the molecular structures and the molecular orbitals. The barrier and mechanism of helical inversion are also reported.