ISOLATION AND MONITORING OF THE ENDOHEDRAL METALLOFULLERENES Y-AT-C-82 AND SC3-AT-C-82 - ONLINE CHROMATOGRAPHIC-SEPARATION WITH EPR DETECTION

The direct coupling of high-performance liquid chromatography (HPLC) with on-line electron paramagnetic resonance (EPR) detection is demonstrated for monitoring separations of endohedral metallofullerenes (M@C-2n). The HPLC-EPR approach readily permits detection of the paramagnetic species, such as Y@C-82 and Sc-3@C-82, in the presence of the dominant empty-cage fullerenes (C-60, C-70) and diamagnetic metallofullerenes (e.g., M(2)@C-2n). The results indicate that on-line EPR provides a noninvasive, selective detector for HPLC metallofullerene separations that is readily adaptable to air-sensitive and/or labile compounds. Specifically, the ''EPR-active'' metallofullerenes, Y@C-82 and Sc-3@C-82, are selectively monitored on-line for an initial separation of the metallofullerene fraction from the dominant empty-cage fullerenes utilizing a combination of polystyrene columns. This preparative ''cleanup'' procedure is followed by HPLC-EPR separation and monitoring of Y@C-82 and SC3@C-82 species using a selective tripodal pi-acidic-phase column (Trident-Tri-DNP) for the final stages of isolation.