SGER: Low Temperature Synthesis of Trimetallic Nitride Template (TNT) Endohedral Metallofullerenes

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

0234292 Dorn This research plans to explore a highly innovative technique for preparing endohedral metallofullerenes. Empty cage fullerenes, such as C60 and C70, and endohedral metallofullerenes are most commonly prepared in a Kratschmer-Huffman electric-arc generator by high temperature vaporization (3000-5000 K) of graphite rods packed with metals and/or metal oxides. The typical endohedral metallofullerenes, such as Ax@C2y (x= 1-3, y=30-50) have been reported with encapsulated metal and non-metal atoms, but are typically formed in low yields (< 0.5 %) with multiple isomers of low symmetry. The PI's research group has recently reported the first class of stable endohedral metallofullerenes, A3-xBxN@C2y (x=0-3, A,B=metal, y=34, 39, 40), e.g., Sc3N@C80, formed by a trimetallic nitride template (TNT) process in significantly improved yields. For example, the archetypal Sc3N@C80 is stable in air to temperatures of 600-650 K or in nanotube "peapods" in vacuo to temperatures in excess of 1300 K. The discovery of a more rational synthesis for the preparation of the trimetallic nitride template (TNT) endohedral metallofullerenes at lower temperatures would open new vistas for these unique materials in a wide range of electronic, optoelectronic, magnetic, catalytic, nanomechanical, and medical applications. The high stability of the TNT endohedral metallofullerenes suggests new avenues toward a more rational synthesis of these unique materials. The recent success in preparing C60 by pyrolysis of precursor hydrocarbons at lower temperatures is an example of this strategy. This success, coupled with the declining cost of empty-cage C60, suggests the possibility of using this prominent fullerene, C60 as a precursor for endohedral metallofullerenes. Preliminary chromatographic retention time and mass spectrometry data clearly identify the TNT endohedral metallofullerene Sc3N@C80 as a major product of this new lower temperature synthesis. Several other empty-cages are also produced C70 and C84 as well as several new endohedral metallofullerenes. These results are extraordinary, although much fundamental research is critically needed to exploit the potential for preparing these TNT endohedral metallofullerenes in large-scale quantities. The specific aims of this study are to: optimize operating parameters of the quartz tube batch reactor for high yield, lower temperature production of TNT endohedral metallofullerenes such as Sc3N@C80; isolate and characterize new endohedral metallofullerenes; elucidate the mechanism(s) and key intermediates involved in this lower temperature reaction utilizing isotopic tracers (15 N and 13 C); and construct a continuous reactor for enhanced production of the TNT endohedral metallofullerenes.