Study on synthesis, structure and physical properties of metal endohedral C_<60>, and its development to new materials

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Purified samples of metal endohedral C_<60> (M@C_<60>) have been prepared through the present project, and their structure and physical properties have been studied by XANES, EXAFS, Raman, UV-VIS-Near IR absorption, ESR and static susceptibility measurements. Large amounts of soots containing Eu@C_<60> and Dy@C_<60> were synthesized by arc-heating of metal oxide / graphite composite rods. The soot of Eu@C_<60> was sublimed at 450℃ under 10^<-6> Torr in order to eliminate Eu endohedral higher fullerenes, and the sublimate obtained was dissolved into a distilled aniline by a supersonic irradiation. On the other hand, the soot of Dy@C_<60> was directly dissolved into the distilled aniline. After repeating high performance liquid chromatography (HPLC) five times, the fraction exhibiting a single peak in the HPLC profile was collected, and the sample quality was checked by TOF-mass spectrum. The purity of Eu@C_<60> and Dy@C_<60> samples was 〜 99 %. The XANES of Eu@C_<60> and Dy@C_<60> showed that the valences of Eu and Dy were +2 and +3, respectively. The valences are accordance with those of Eu@C_<82> and Dy@C_<82>. The distance between Dy and the first nearest C atoms (Dy-C(1), and that between the Dy and the second nearest C atoms (Dy-C(2)) were determined to be 2.39(1) and 2.67(3) Å, respectively, on the basis of Dy L_<III>-edge EXAFS. The results show that the Dy atom lies on five-membered ring inside C_<60> cage ; the Dy is located at the off-center position by 1.25 Å. The Ag(2) Raman peak of Dy@C_<60> was observed at 1450 cm^<-1>. This shows that three electrons transfer from the Dy to the C_<60> cage. The ESR of Dy@C_<60> exhibited the g-factor of 2.0050 and line width of 4.5 G at 298 K. The ESR of Dy^<3+> was observed at 4.0 K, which implies that the spin of C_<60> appears by three-electrons transfer from Dy atom. The study on structure and physical properties of M@C_<60>・carbon nanotube hybrid materials in nanometer scale is now in progress.