Red Emissive Double Aza[7]helicenes with Antiaromaticity / Aromaticity Switching via the Redox‐Induced Radical Cation and Dication Species. (24th March 2023)

• Record Type: Journal Article
• Authors: Li, Chenglong; Zhang, Chen; Li, Pengfei; Jia, Yawei; Duan, Jiaxian; Liu, Meiyan; Zhang, Niu; Chen, Pangkuan
• Is Part Of: Angewandte Chemie. Volume 135:Number 18(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-24
• Subjects: Antiaromaticity -- Aza[7]Helicene -- Chirality -- Radical Cation -- Red Emission; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202302019
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: We herein present the synthetic approach to a new antiaromatic double aza[7]helicene C that features NN‐embedded polycyclic aromatic hydrocarbons (PAHs). This heteroatom‐doped helicene showed a rarely obtained long‐wavelength emission and far‐red circularly polarized luminescence (CPL) in the solid state. These optical and chiroptical properties could be ascribed to both the NN‐PAH core structure and the further extension through angular ring fusions. Such a unique electronic structure also culminated in facile chemical oxidations of neutral C to the positively charged chiral radical (C ⋅ + ) and dication species (C 2+ ). Interestingly, DFT computations revealed that the pyridazine central core showed an antiaromaticity‐to‐aromaticity switching, in contrast to the inversed transition for the helical periphery in cationic states. The reported approaches are anticipated to lead to the development of further redox‐active chiral systems for potential applications in chiroptoelectronics, spintronics as well as fluorescent bioimaging. Abstract : A pyridazine core structure with antiaromatic character has been utilized to synthesize a double aza[7]helicene with rarely accessible chiroptical properties in the red region as well as redox‐active behaviour. This chiral polyaromatic hydrocarbon system shows oxidation‐state‐dependent aromaticity/antiaromaticity switching via oxidation‐induced cation species.