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Fused Quinoidal Dithiophene‐Based Helicenes: Synthesis by Intramolecular Radical–Radical Coupling Reactions and Dynamics of Interconversion of Enantiomers
Author(s) -
Li Guangwu,
Matsuno Taisuke,
Han Yi,
Wu Shaofei,
Zou Ya,
Jiang Qing,
Isobe Hiroyuki,
Wu Jishan
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202100606
Subject(s) - racemization , intramolecular force , chemistry , enantiomer , dehydrogenation , density functional theory , molecule , computational chemistry , photochemistry , stereochemistry , organic chemistry , catalysis
A series of fused quinoidal dithiophene‐based double and triple helicenes ( 1‐M , 2‐M , 2‐M‐Cl , 3‐M , 3‐M‐Cl ) were synthesized by intramolecular radical–radical coupling followed by oxidative dehydrogenation reaction. These helical molecules show dynamic interconversion of enantiomers in solution as revealed by variable‐temperature NMR measurements, and the energy barriers are correlated to the substituents and topological structures. Notably, dynamic high performance liquid chromatography was used to quantitatively investigate the room‐temperature racemization process between the (P,P,M)‐ and (P,M,M)‐ enantiomers of the triple helical 3‐M‐Cl , which gave an interconversion energy barrier in consistent with density functional theory calculations. Their optical and electrochemical properties are dependent on the fusion mode. Our studies provide both new synthetic strategy and new dynamic analytical method for helicenes with unique electronic structure.