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Updated: Mar 29, 2026

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
Published on: September 18, 2016
Cethrene: A Helically Chiral Biradicaloid Isomer of Heptazethrene
Prince Ravat1, Tomáš Šolomek1, Michel Rickhaus1
1Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland.
Abstract:
We report the synthesis and properties of "cethrene", the only helically chiral isomer of heptazethrene with a biradicaloid singlet ground state. Cethrene gives a well-resolved EPR spectrum at room temperature and its structure was confirmed by 2D NMR and absorption spectroscopies. Our experiments and calculations show that the helical twist affects its electronic properties and decreases the singlet-triplet energy gap when compared to that of planar heptazethrene. Cethrene undergoes an intramolecular cyclization within several hours at room temperature.
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