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 fee lattice of C 60 . The 13 C NMR spectrum of C 60 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 C 60 molecules. Exposure of C 6 o 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 C 60 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 C 60 and C 70 with hydrogen molecules.

Effect of Crystalline Structure and Impurity Content of C60 Thin Films on the Order/Disorder Phase Transition

“…Given the large size of the interstitial sites in the C 6 o crystal (the corresponding voids are more than 4 A in diameter) molecular oxygen from air is known to diffuse readily into this solid even at room temperature [15]. We revealed that post-grown exposure of our films to air leads to an increase in their oxygen content [ 16] and, in turn, to reduction in the Aa/a and Tc values.…”

Solid State Physicochemical Properties and Applications of Organic and Metallo- Organic Fullerene Derivatives

“…Pristine C 60 in powder and thin-film form is unstable under ambient conditions. In fact, due to the relatively large (on the atomic scale) interstitial voids between the molecules in pristine fullerite, molecular oxygen readily diffuses into it [10]. Subsequent illumination by light triggers photochemical reactions leading to C-O binding and disruption of the fullerene cages.…”

Interaction Between C60 and Gases under Pressure

“…Early NMR studies showed that oxygen diffused reversibly into the octahedral sites at atmospheric pressure and room temperature with equilibrium filling fractions of at most a few percent [25,26]. At high pressures, 10-100 MPa, both O 2 and N 2 diffuse slowly into the C 60 lattice, so that they may fill a large fraction of the octahedral sites over a time of several days [27,28].…”

“…The intercalation compounds of oxygen have been studied by many methods. NMR can give information on the average number of filled octahedral sites [25][26][27]29] and also shows that the oxygen resides at the center of the interstitial sites with no sign of charge transfer or chemical bonding [26]. Inelastic neutron scattering and Raman scattering also shows that although some vibration modes of the intercalated molecules soften appreciably when the molecules are confined within the C 60 interstitial sites, this has no measurable effect on the vibrational and librational properties of the C 60 lattice [28].…”