Studies of Top-Down Mechanistic Processes of Fullerene and Metallofullerene Formation for Cages Greater Than Ninety Carbons

The elucidation of a mechanistic theory for fullerene formation in electric-arc plasmas, laser ablation, and interstellar space has been a subject of considerable interest over the past two decades. For many years, a “bottom-up” theory of fullerene formation from C₂ units was dominant.  However, in recent years evidence is emerging suggesting a “top-down mechanism” - that is, fullerenes are formed via shrinkage of giant fullerenes generated from graphene.  Previously, we reported molecular structural evidence implying a top-down mechanism for the asymmetric non-IPR metal carbide metallofullerene, M₂C₂@C₁(51383)-C₈₄ (M=Y,Gd) as a missing link in the mechanism for the formation of smaller, more symmetric metallofullerene cages.  In this paper, we extend the study mechanism to include larger fullerenes, namely the C_3v(134)C₉₄ and D₃(85)C₉₂ cages.