Double Negatively Curved C 70 Growth through a Heptagon‐Involving Pathway

• Published in: Angewandte Chemie Vol. 131; no. 40; pp. 14233 - 14237
• Main Authors: Zhong, Yuan‐Yuan, Chen, Zuo‐Chang, Du, Peng, Cui, Cun‐Hao, Tian, Han‐Rui, Shi, Xiang‐Mei, Deng, Shun‐Liu, Gao, Fei, Zhang, Qianyan, Gao, Cong‐Li, Zhang, Xin, Xie, Su‐Yuan, Huang, Rong‐Bin, Zheng, Lan‐Sun
• Format: Journal Article
• Language: English
• Published: 01.10.2019
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201902154

Abstract All previously reported C 70 isomers have positive curvature and contain 12 pentagons in addition to hexagons. Herein, we report a new C 70 species with two negatively curved heptagon moieties and 14 pentagons. This unconventional heptafullerene[70] containing two symmetric heptagons, referred to as dihept‐C 70 , grows in the carbon arc by a theoretically supported pathway in which the carbon cluster of a previously reported C 66 species undergoes successive C 2 insertion via a known heptafullerene[68] intermediate with low energy barriers. As identified by X‐ray crystallography, the occurrence of heptagons facilitates a reduction in the angle of the π‐orbital axis vector in the fused pentagons to stabilize dihept‐C 70 . Chlorination at the intersection of a heptagon and two adjacent pentagons can greatly enlarge the HOMO–LUMO gap, which makes dihept‐C 70 Cl 6 isolable by chromatography. The synthesis of dihept‐C 70 Cl 6 offers precious clues with respect to the fullerene formation mechanism in the carbon‐clustering process.