Persistent, highly localized, and tunable [4]helicene radicals. Issue 40 (23rd September 2020)

• Record Type: Journal Article
• Authors: Shaikh, Aslam C.; Moutet, Jules; Veleta, José M.; Hossain, Md Mubarak; Bloch, Jan; Astashkin, Andrei V.; Gianetti, Thomas L.
• Is Part Of: Chemical science. Volume 11:Issue 40(2020)
• Page Start: 11060
• Page End: 11067
• Publication Date: 2020-09-23
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0sc04850j
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : We report a series of tunable and persistent [4]-helicene neutral radicals by chemical reduction of the [4]-helicenium cation analogue. EPR spectroscopy and DFT calculations indicate that the unpaired electron is localized at the central carbon atom. Abstract : Persistent organic radicals have gained considerable attention in the fields of catalysis and materials science. 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 our [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.