Intercalation of molecular species into the interstitial sites of fullerene

Abstract

Molecular species were found to diffuse readily into the octahedral interstitial sites of the fcc lattice of C₆₀. The ¹³C NMR spectrum of C₆₀ under magic angle spinning (MAS) conditions consisted of a primary resonance at 143.7 ppm and a minor peak shifted 0.7 ppm downfield. The downfield shift obeys Curie's law and is attributed to the Fermi-contact interaction between paramagnetic oxygen molecules and all 60 carbon atoms of rapidly rotating adjacent C₆₀ molecules. Exposure of C₆₀ to 1 kbar oxygen for 1.75 h at room temperature resulted in a spectrum of seven evenly spaced resonances corresponding to the filling of 0 to 6 of the adjacent octahedral interstitial sites with oxygen molecules. The distribution of site occupancies about a C₆₀ molecule provided evidence that the intercalation process is controlled by diffusion kinetics. Exposure to 0.14 kbar hydrogen gas at room temperature for 16 h filled a substantial fraction of the interstitial sites of C₆₀ and C₇₀ with hydrogen molecules.