Planet pineapple: The structures of two isolated pentagon rule (IPR)‐violating chlorofullerenes (C50Cl10 and C64Cl4; see picture) are determined by X‐ray crystallography and their stabilities rationalized by relief of strain at the active pentagon‐fusion carbon atoms whilst maintaining the aromaticity of their carbon skeletons.

A carbon heptagon ring is a key unit responsible for structural defects in sp2-hybrized carbon allotropes including fullerenes, carbon nanotubes and graphenes, with consequential influences on their mechanical, electronic and magnetic properties. Previous evidence concerning the existence of heptagons in fullerenes has been obtained only in off-line halogenation experiments through top-down detachment of a C2 unit from a stable fullerene. Here we report a heptagon-incorporating fullerene C68, tentatively named as heptafullerene[68], which is captured as C68Cl6 from a carbon arc plasma in situ. The occurrence of heptagons in fullerenes is rationalized by heptagon-related strain relief and temperature-dependent stability. 13C-labelled experiments and mass/energy conservation equation simulations show that heptafullerene[68] grows together with other fullerenes in a bottom-up fashion in the arc zone. This work extends fullerene research into numerous topologically possible, heptagon-incorporating isomers and provides clues to an understanding of the heptagon-involved growth mechanism and heptagon-dependent properties of fullerenes.

A smaller fullerene C56 (#913) is stabilized, isolated, and crystallographically characterized as C56Cl10. The geometric parameters of C56Cl10 imply the otherwise unstable cage of C56 can be stabilized by chlorination through releasing its surface strains and maintaining fragmental aromaticity. An unexpected C Cl...ClC short contact, as well as the linear alignment with pearl-necklace-shaped, is revealed in C56Cl10 crystal.

Pure non-IPR (isolated-pentagon-rule) C60 isomer has rarely been investigated experimentally. The recently reported availability of #1809C60Cl8 opens an avenue for experimental investigation of #1809C60, a C 2v -symmetric C60 isomer having two pairs of fused pentagons. Herein, the experiments on #1809C60 were performed on the basis of thermal dechlorination of #1809C60Cl8 in the solid state and gas phase. #1812C60Cl6 was employed for comparative study. As determined by Raman and other methods, #1809C60 from thermal decomposition of #1809C60Cl8 crystals readily coalesces to form carbon solid with a collapsed crystal lattice. In contrast, dechlorination via thermal spray of #1809C60Cl8 in the gas phase is feasible for investigation of monodispersed all-carbon C60 isomer, because the existence of #1809C60 in the gas phase has been confirmed by experimental evidence from mass spectrometry and high-performance-liquid-chromatography.