Carbon arc production of heptagon-containing fullerene[68]

Abstract

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.

Closed network growth of fullerenes

“…S6). Interestingly, a heptagon-containing C 68 fullerene, although exohedrally stabilized by chlorine, has recently been found to form in carbon vapour 35 . C 64 and all larger clusters possess isotopic distributions that conform to growth by sequential carbon addition steps originating with the C 60 precursor.…”

From C58to C62and back: Stability, structural similarity, and ring current

“…The focus of studies of classical fullerenes is now moving on to applications [6,7]. However, an increasing number of experimental and theoretical observations indicate that non-classical isomers play an important role in the formation of metallofullerenes and fullerene derivatives [8][9][10]. Even for the fullerenes themselves, formation mechanisms are still unclear in terms of the roles of heptagons and/or squares [11].…”

Synthesis of Long‐Sought C66 with Exohedral Stabilization

“…a Krätschmer-Huffman graphite-arc-discharge process involving chlorine, [17] our 13 C-labeling experiments established the growth of pristine fullerenes in the arc zone at 2000-2500 K and their subsequent capture/stabilization by chlorination beyond the arc zone. [18] Therefore, the capture of #4348 C 66 as a chlorofullerene is reasonable in the present synthesis in a carbon arc in the presence of carbon tetrachloride.…”