Purification of Trimetallic Nitride Templated Endohedral Metallofullerenes by a Chemical Reaction of Congeners with Eutectic 9-Methylanthracene

Abstract

The availability of pure samples is a major hurdle in the study of trimetallic nitride templated endohedral metallofullerenes (TNT EMFs). Current HPLC methods of purification are costly, nonrecyclable, and take considerable time. Reported herein is a solvent-free reaction of crude soot extract (empty-cage and Sc or Lu TNT EMFs) in molten 9-methylanthracene that affords almost complete conversion of empty-cage fullerenes to 9-methylanthracene adducts, while leaving TNT EMFs unreacted. After the recovered extract is washed with diethyl ether, the washed extract can then be applied to a silica gel column and subsequently flushed with toluene. To illustrate for Sc3N@C80, the sample was purified to ∼60% in a time period of <24 h. Final one-step HPLC purification provided high-purity TNT EMF samples (>99%) in an expeditious and less costly manner.

Chemische, elektrochemische und Struktureigenschaften von endohedralen Metallofullerenen

“…Die Methode hat also den Haken, dass reine Proben des D 5 h ‐ und I h ‐Isomers erst nach mehreren Wochen zur Verfügung stehen. Kürzlich berichteten Dorn und Mitarbeiter von einer anderen Trennmethode, bei der ebenfalls leere Fullerene selektiv eine Diels‐Alder‐Reaktion eingehen, während das Metallnitrid‐EMF nicht reagiert 47c…”

An Efficient Method to Separate Sc3N@C80Ih and D5h Isomers and Sc3N@C78 by Selective Oxidation with Acetylferrocenium [Fe(COCH3C5H4)Cp]+

“…The first reported example to separate TNT‐EMFs from ECFs in a single step used a cyclopentadiene‐functionalized Merrifield resin 17. A similar methodology was later reported by using eutectic 9‐methylanthracene, which gave a mixture of empty fullerene adducts and unreacted TNT‐EMFs (Sc 3 N@C 78 and Sc 3 N@C 80 isomers) 18. This method only allows the separation of Sc 3 N@C 68 from the rest of the TNT‐EMFs, but it is not an efficient method because Sc 3 N@C 68 cannot be recovered.…”

“…[17] A similar methodology was later reported by using eutectic 9-methylanthracene, which gave a mixture of empty fullerene adducts and unreacted TNT-EMFs (Sc 3 N@C 78 and Sc 3 N@C 80 isomers). [18] This method only allows the separation of Sc 3 N@C 68 from the rest of the TNT-EMFs, but it is not an efficient method because Sc 3 N@C 68 cannot be recovered. Another simple nonchromatographic method called "stir and filter approach" (SAFA) not only allows the separation of ECFs from TNT-EMFs, but also the separation of Sc 3 N@C 68 and Sc 3 N@C 78 from the Sc 3 N@C 80 isomers.…”

2‐Aminoethanol Extraction as a Method for Purifying Sc3N@C80 and for Differentiating Classes of Endohedral Fullerenes on the Basis of Reactivity

“…This method does not utilize a mobile phase and can produce TN endohedral metallofullerenes in 99 % purity in 5 h. Dorn and co‐workers developed another separation method that involves reacting the carbon soot with molten 9‐methylanthracene and subsequently removing the empty cage/9‐methylanthracene adducts by repeated washing with diethyl ether. Chromatography on silica gel followed by HPLC then produces the purified TN endohedral 16. Stevenson and co‐workers have recently published a method for TN endohedral fullerene enrichment that is based on precipitation of relatively electron‐rich metallofullerenes with Lewis acids 17–20.…”