La₂@C₇₂:  Metal-Mediated Stabilization of a Carbon Cage

Abstract

In this study, we report production, isolation, and characterization for the relatively small endohedral metallofullerene, La 2 @C 72. As described, La 2 @C 72 is readily isolated from conventional electric-arc-generated carbon/metal soot. This new species was purified by HPLC chromatography and characterized by laser desorption mass spectrometry and UV-vis spectroscopy. The mass spectrum also demonstrates the presence of the monometal species, La@C 72 , but the absence of empty-cage C 72. Since empty-cage C 72 has not been successfully isolated to date, the results of the present study are in agreement with the argument for metalmediated stabilization of the C 72 carbon cage by lanthanum ions. The chromatographic retention data suggest that the electronic structure of La 2 @C 72 is consistent with a (La 3+) 2 @C 72 6species and the prediction of a relatively small dipole moment.

A systematic study on the generation of multimetallic lanthanide fullerene ions by laser ablation mass spectrometry

“…In fact, in the early carbon‐arc evaporation experiments, di‐metallofullerenes of (M = Ce, Tb and Ho) were also observed accompanied by the generation of the mono‐metallofullerenes . Noticeably, many di‐metallofullerenes, includingLa 2 C 72 , La 2 C 78 , La 2 C 80 , Ce 2 C 72 , Ce 2 C 78 , Ce 2 C 80 , and Pr 2 C 80 , and tri‐metallofullerenes, including Er 3 C 74 , Tb 3 C 80 and Dy 3 C 98 , have now been successfully synthesized, separated and characterized . These synthesized EMFs generally have much smaller fullerene cages than the metallofullerene ions that we observed here, strongly supporting the two mechanisms behind them, that is, the bottom‐up mechanism in arcing experiments and the top‐down mechanism in the laser ablation of graphene experiments …”

“…A wide range of studies have been devoted to encaging different metal atoms and metallic clusters into fullerenes of different sizes . EMFs containing rare‐earth metals and nearby metal elements have been synthesized and investigated with the aid of macroscopic generation methods such as arc discharge . The generation of new EMFs that encage new types of metals and clusters is always a very attractive area of study.…”

Strain Release of Fused Pentagons in Fullerene Cages by Chemical Functionalization

“…[32] Exohedral addition of functional groups results in the transformation of as p 2carbon atom into asp 3 -carbon atom accompanied by achange in the bond angles of the carbon atoms at the pentagon fusions,t hereby offering another opportunity to stabilize the non-IPR fullerenes.I ndeed, this concept was experimentally verified by the successful isolation of #271 C 50 Cl 10 (the number after #isthe spiral label based on the Fowler-Manolopoulos spiral algorithm [12] )i n2 004 as the first non-IPR fullerene stabilized by exohedral functionalization and which represents the smallest fullerene with the cage containing DFPs. [33] Such an in situ exohedral chlorination strategy was later extended to stabilize other non-IPR fullerenes with cage sizes ranging from C 56 to C 78 ,w hich are mostly relatively small cages. [34][35][36][37][38][39][40][41][42][43][44] To interpret these exohedral stabilization effects, Xie and co-workers proposed the "strain-relief" and "localaromaticity" principles, [4] which are helpful for predicting unknown non-IPR fullerene derivatives.…”

Freisetzung der Spannung kondensierter Fünfringe des Fullerenkäfigs durch chemische Funktionalisierung

“…[12] )e xperimentell bestätigt, das als erstes Nicht-IPR-Fulleren durch exohedrale Funktionalisierung stabilisiert wurde und das kleinste Fulleren ist, dessen Käfig DFP enthält. [33] Später wurde solch eine Strategie der exohedralen Insitu-Chlorierung ausgeweitet, um weitere Nicht-IPR-Fullerene,b asierend auf einer von C 56 bis C 78 reichenden Reihe von Fullerenkäfigen, zu stabilisieren, die meistens relativ kleine Käfige aufwiesen. [34][35][36][37][38][39][40][41][42][43][44] Um diese Effekte der exohedralen Stabilisierung zu interpretieren, postulierten Xie et al die Prinzipien "Spannungsentlastung" und "lokale Aromatizität", [4] die zudem hilfreich fürd ie Vorhersage unbekannter Nicht-IPR-Fullerenderivate sind.…”