Dual Stabilization of a Tri‐Metallofullerene Radical Er₃@C₈₀: Exohedral Derivatization and Endohedral Three‐Center Bonding

Abstract

The enclosed space within fullerene molecules, capable of trapping metal clusters, offers an opportunity to investigate the behavior of metal atoms in a highly confined sub‐nanometer environment. However, the studies on tri‐metallofullerenes M3@C80 have been very limited due to their difficult obtainability. In this paper, we present a new method for obtaining a tri‐metallofullerene Er3@C80 through exohedral modification of the fullerene cage. Our findings reveal that Er3@C80 exhibits a radical character and can react with the dichlorobenzene radical to generate a stable derivative Er3@C80PhCl2. Theoretical calculations demonstrate the presence of a three‐center two‐electron metal‐metal bond in the center of the fullerene cage. This bond serves to counterbalance the Coulomb repulsion between the Er ions. Consequently, both exohedral derivatization and endohedral three‐center bonding contribute to the substantial stability of Er3@C80PhCl2. Furthermore, molecular dynamics simulations indicate that the Er3 cluster within the molecule possesses a rigid triangle structure. The availability of M3@C80 derivatives opens avenues for future investigations into interactions among metal atoms, such as magnetic coupling, within fullerene cages.