We report an efficient method for the preparation and purification of the I-h and the D-5h isomers of Tm3N@C-80. Following preparation in a Kratschmer-Huffman electric-arc generator, the Tm3N@C-80 isomers were obtained by a chemical separation process followed by a one-stage isomer selective chromatographic high-performance liquid chromatography (HPLC) separation (pyrenyl, 5PYE column). The HPLC chromatographic retention behavior on a pentabromobenzyl (5PBB) column suggests a charge transfer of similar to 6 electrons; [M3N](6+)@C-80(6-) and the chromatographic retention mechanisms of the I-h and the D-5h isomers of Tm3N@C-80 on both 5PBB and 5PYE columns are discussed. Single-crystal X-ray diffraction data demonstrate that the Tm3N cluster has a planar structure but represents a tight fit for trapping the Tm3N cluster inside the I-h- and the D-5h-C-80 cages. Specifically, the Tm atoms punch out the cage carbon atoms adjacent to them, The "punched out" effect can be demonstrated by cage radii and pyramidal angles at cage carbon atoms near the Tm atoms. The magnetic susceptibility (chi T) for Tm3N@ I-h-C-80 was found to exhibit Curie-Weiss behavior with C = 23.4 emu center dot K/mol, which is consistent with the calculated value for three uncoupled Tm3+ ions by considering the spin and orbital contributions with no quenching of the orbital angular momentum (L = 5, S = 1, and J = 6; C-calcd = 23.3 emu center dot K/mol). The electrochemical measurements demonstrate that both the I-h and the D-5h isomers of Tm3N@C-80 have a large electrochemical gap.