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Multiple Fused Anthracenes as Helical Polycyclic Aromatic Hydrocarbon Motif for Chiroptical Performance Enhancement
Author(s) -
Fujise Kei,
Tsurumaki Eiji,
Fukuhara Gaku,
Hara Nobuyuki,
Imai Yoshitane,
Toyota Shinji
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.202000394
Subject(s) - helicene , enantiopure drug , anthracene , enantiomer , chemistry , molecule , polycyclic compound , circular dichroism , polycyclic aromatic hydrocarbon , conjugated system , hydrocarbon , crystallography , stereochemistry , photochemistry , enantioselective synthesis , organic chemistry , catalysis , polymer
Polycyclic aromatic hydrocarbons consisting of three fused anthracene units were designed as new π‐conjugated compounds having helical structures. These expanded helicenes were synthesized by Pt‐catalyzed cycloisomerization of the corresponding ethynyl‐substituted precursors. The nonplanar and helical structure was confirmed by X‐ray analysis and DFT calculations, and the barrier to helical inversion was estimated to be 34 kJ mol −1 . The enantiomers of the diphenyl derivative were successfully resolved by chiral HPLC. Enantiopure samples showed good chiroptical performance in the CD (|Δ ϵ | 1380 L mol −1 cm −1 ) and CPL (| g lum | 0.013) spectra, and these values were considerably large for simple organic molecules. The unique chiroptical properties are discussed on the basis of the molecular structure and the electronic state with the aid of time‐dependent DFT calculations.