²³Na and ¹³C NMR investigation of Na₂C₆₀ and Na₆C₆₀ fullerides

Laboratoire Charles Coulomb, Université Montpellier 2, Place E. Bataillon, 34095, Montpellier, France

^a e-mail: Ferid.Rachdi@univ-montp2.fr

Abstract

We report on ²³Na and ¹³C NMR measurements on Na₂C₆₀ and Na₆C₆₀ compounds. The ²³Na NMR spectrum of A₂C₆₀ shows one line at 73 ppm and the one of A₆C₆₀ presents two lines at 73 and 147 ppm. The intensity ratio of the latter lines is about 2:1. According topreviously reported x-ray data we attribute the line at 147 ppm to the Na tetramers in the octahedral sites and the line at 73 ppm to the Na cations in the tetrahedral ones which are singly occupied.

The room-temperature ¹³C NMR spectra of Na₂C₆₀ and Na₆C₆₀ samples present a narrow isotropic line at 172 and 176 ppm, respectively. The Na₆C₆₀ resonance is shifted 20 ppm more down field than the resonances of A₆C₆₀ compounds with heavier alkalis, indicating a partial charge transfer to the threefold degenerate t_1u level which is totally filled in the latter compounds.