Stoichiometric synthesis of fullerene compounds with lithium and sodium and analysis of their IR and EPR spectra

A modified method is proposed for preparing fullerene compounds with alkali metals in a solution. The compounds synthesized have the general formula Me n C60(THF)x, where Me = Li or Na; n=1–4, 6, 8, or 12; and THF = tetrahydrofuran. The use of preliminarily synthesized additives MeC10H8 makes it possible to prepare fullerene compounds with an exact stoichiometric ratio between C 60 − and Me +. The IR and EPR spectra of the compounds prepared are analyzed and compared with the spectra of their analogs available in the literature. The intramolecular modes T u (1)-T u (4) for the C 60 − anion are assigned. The splitting of the T u (1) mode into a doublet at room temperature for Me n C60(THF)x (n=1, 2, 4) compounds indicates that the fullerene anion has a distorted structure. An increase in the intensity of the T u (2) mode, a noticeable shift of the T u (4) mode toward the long-wavelength range, and an anomalous increase in the intensity of the latter mode for the Li3C60(THF)x complex suggest that, in the fullerene anion, the coupling of vibrational modes occurs through the charge-phonon mechanism. The measured EPR spectra of lithium-and sodium-containing fullerene compounds are characteristic of C 60 − anions. The g factors for these compounds are almost identical and do not depend on temperature. The g factor for the C 60 − anion depends on the nature of the metal and differs from the g factor for the C 60 − anion.