Interconversions between Uranium Mono-metallofullerenes: Mechanistic Implications and Role of Asymmetric Cages

The isolation and structural characterization of three new monometallic uranium metallofullerenes, U@D₂(21)-C₈₄, U@C(15)-C₈₆, and U@C₁(11)-C₈₆, allowed us to complete an interconversion map for all the characterized uranium mono-metallofullerenes. The topological analysis reveals that asymmetric fullerene cages, which may be formed by roll and wrap processes directly from graphene, are the starting points for a series of highly symmetric fullerene structures via top-down and bottom-up growth mechanisms. Moreover, some asymmetric intermediates, such as C₁(28324)-C₈₀, can serve as precursors to form either larger cages in consecutive growing processes or smaller cages during cascade shrinking processes. This work provides evidence for both top-down and bottom-up processes happening simultaneously during the arcing processes. This study also sheds light on the prediction of possible cage structures for minor products produced in low yields in the soot.