Nanographene with Multiple Embedded Heptagons: Cascade Radical Photocyclization. (4th March 2022)

• Record Type: Journal Article
• Authors: Qiu, Zhen‐Lin; Chen, Xuan‐Wen; Huang, Yu‐Dong; Wei, Rong‐Jing; Chu, Ke‐Shan; Zhao, Xin‐Jing; Tan, Yuan‐Zhi
• Is Part Of: Angewandte Chemie. Volume 134:Number 18(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-04
• Subjects: Heptagons -- Nanographene -- Photocyclization -- Structure Elucidation -- Synthetic Methods; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202116955
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Although heptagons are widely found in graphenic materials, the precise synthesis of nanocarbons containing heptagons remains a challenge, especially for the nanocarbons containing multiple‐heptagons. Herein, we show that photo‐induced radical cyclization (PIRC) can be used to synthesize multi‐heptagon‐embedded nanocarbons. Notably, a nanographene containing six heptagons (1 ) was obtained via a six‐fold cascade PIRC reaction. The structure of 1 was clearly validated and showed a Monkey‐saddle‐shaped conformation. Experimental bond analysis and theoretical calculations indicated that the heptagons in 1 were non‐aromatic, whereas the peripheral rings were highly aromatic. Compared to planar nanographene with the same number of π electrons, 1 had a similar optical gap due to a compromise between the decreased conjugation in the wrapped structure and enhanced electronic delocalization at the rim. Electrochemical studies showed that 1 had low‐lying oxidation potentials, which was attributed to the nitrogen‐doping. Abstract : Photo‐induced radical cyclization was used in the synthesis of nanocarbons with embedded heptagons, providing a new approach towards nanocarbons with novel topologies. The nanographene reported herein bears six heptagons, representing the nanocarbon containing the largest number of heptagons by organic synthesis reported to date. The embedded heptagons distort the graphene core into a Monkey‐saddle‐shaped conformation.