Title: Double Negatively Curved C70 Growth through a Heptagon‐Involving Road

Authors: Yuan-Yuan Zhong,  Zuo-Chang Chen,  Peng Du,  Cun-Hao Cui,  Han-Rui Tian,  Xiang-Mei Shi,  Shun-Liu Deng,  Fei Gao,  Qianyan Zhang , Cong-Li Gao,  Xin Zhang,  Su-Yuan Xie, Rong-Bin Huang , Lan-Sun Zheng

Abstract:

All previously reported C70 isomers have positive curvature and contain 12 pentagons in addition to hexagons. Here, we report a new C70 species with 2 negatively curved moieties of heptagons and 14 pentagons. This unconventional heptafullerene[70] containing two symmetric heptagons, referred to dihept‐C70, grows in the carbon arc by a theoretically supported heptagon‐involved pathway in which the carbon cluster of a previously reported C66 undergo successive C2 insertion via a known heptafullerene[68] (hept‐C68) intermediate with low energy barriers. As identified by X‐ray crystallography, the occurrence of heptagon facilitates a reduction in the angle of the π‐orbital axis vector in the fused pentagons to stabilize the dihept‐C70. Chlorination at the intersection of a heptagon and two adjacent pentagons can greatly enlarge the HOMO‐LUMO gap, which makes dihept‐C70Cl6 isolable through chromatography. The retrieve of dihept‐C70Cl6 offers precious clues to understanding the fullerene formation mechanism in the carbon‐clustering process.

Full-Link: https://onlinelibrary.wiley.com/doi/10.1002/anie.201902154