Persistent, Highly Localized, and Tunable [4]Helicene Radicals

07 August 2020, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


Persistent organic radicals have gained considerable attention in the fields of catalysis and material sciences. In particular, helical molecules are of great interest for the development and application of novel organic radicals in optoelectronic and spintronic materials. Here we report the syntheses of easily tunable and stable neutral quinolinoacridine radicals under anaerobic conditions by chemical reduction of their quinolinoacridinium cation analogs. The structures of these [4]helicene radicals were determined by X-ray crystallography. Density functional theory (DFT) calculations, supported by Electron paramagnetic resonance (EPR) measurements, indicate that over 40% of spin density is located at the central carbon of the [4]helicene radicals regardless of their structural modifications. The localization of the charge promotes a reversible oxidation to the cation upon exposure to air. This unusual reactivity toward molecular oxygen was monitored via UV-Vis spectroscopy.


Stable [4]helicene radical
organic radical
Density functional calculations
EPR spectroscopy
X-ray crystallography

Supplementary materials

Gianetti Helicene radical ESI


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