Nondestructive Quantitative Analysis of Lithium Ion-Endohedral Fullerene Salt (Li(+)@C(60)·PF(6) (-)) via (19)F NMR Spectroscopy

A quantitative analysis of the lithium ion-endohedral fullerene salt, Li(+)@C(60)·PF(6) (-) (1), was performed using (19)F nuclear magnetic resonance (NMR) spectroscopy. To establish a robust quantitative (19)F NMR (qNMR) method, experimental parametersincluding spin-lattice relaxation time (T (1)), relaxation delay, and offset frequencywere optimized using tetrabutylammonium hexafluorophosphate (TBA(+)·PF(6) (-)) as a model compound and α,α,α-trifluorotoluene (PhCF(3)) as an internal standard. The purity of 1 was determined using a calibration curve constructed from (19)F NMR measurements, which effectively minimized systematic errors. The purity value obtained via this nondestructive qNMR method was approximately 95%, showing excellent agreement with quantitative results obtained from inductively coupled plasma atomic emission spectroscopy (95.1%). This method offers a rapid, specific, and nondestructive alternative for the purity evaluation of endohedral metallofullerenes allowing for complete sample recovery.