Abstract: The endrohel metallofullerene, Gd@C₈₂, Gd@C₈₀, Gd₂@C₈₀ were synthesized by using K-Hmethod. The technique of two-step of high pressure and high temperature extraction with 1,3,5 trimethylbenzene(first step) and pyridine(second step) has been successfully utilized to extract metallofullerene of Gd@C₈₂. The gas-phase negative ions of fullerenes C_n(n=60, 70, 78, 82, 84…) and metallofullerene (Gd@C₈₂ ) have been studied by the ESI-MS, REC-MSand MALDI-TOF-MS. The differences among the mass spectra of ESI-MS, REC-MSand MALDI-TOF MShave been observed and explained. In contrast to the empty fullerene C₈₂, the metallofullerene Gd@C₈₂ should have a larger HOMO-LUMOgap. Experimental results suggest that Gd@C₈₂ is polarized and Gd ³⁺ located in the off center position of C₈₂ cage after Gd ³⁺ is trapped into C₈₂ cage.

Key words: Two-step method of high pressure and temperature extraction, Gd@C₈₂ molecule, ESI-MS, HOMO-LUMO, Polar molecule, Off-center position