Endohedral metallofullerenes M@C82 (M=La, Y):: synthesis and transport properties

Endohedral metallofullerenes M@C-2n (M=La, Y) were synthesized by the arc-discharge method using optimum electric arc parameters. It was also shown that an organic solvent (N,N-dimethylformamide) is successfully used in selective extraction of M@C-2n. We identified the resulting products by mass spectrometry, electron spectrophotometry, EPR and X-ray fluorescence spectroscopy. The resulting N,N-dimethylformamide extracts of La@C-2n and Y@C-2n are shown to be free of empty fullerenes and appear as a mixture of endometallofullerenes M@C-2n whose main ingredient is M@C-82 (similar to80 wt%). Transport properties of the extracts of La@C-82 and Y@C-82 were studied using pressed pellets. It was found that oxygen and heat treatment affect conductivity of endometallofullerenes. Heat treatment results in a three-order increase of conductivity from 10(-5) upto 10(-2) Ohm(-1) cm(-1) (C) 2003 Elsevier Science Ltd. All rights reserved.