THE DARK REACTION OF C-60 AND OF C-70 WITH MOLECULAR-OXYGEN AT ATMOSPHERIC-PRESSURE AND TEMPERATURES BETWEEN 300 K AND 800 K

The solid fullerenes C-60 and C-70 react in deliberate and adventitiou s situations with molecular oxygen in a wide range of temperatures. Us ing thin films and polycrystalline bulk samples with well-defined stru ctures and chemical histories we investigated the complex process from molecular intercalation over atomic adduct formation to deep oxidatio n and polymerisation which together describe the oxidation reaction. A combination of photoemission (UPS, XPS) photoabsorption (XAS), FT-IR, temperature-programmed and isothermal gravimetric measurements and DS C allowed to identify the existence and gradual interconversion of the three types of solid products besides the gas phase products CO and C O2. Both fullerenes react along the same reaction path. The difference of the molecular structures results in different activation barriers in the initial step of intercalation and in the final step of cage-ope ning. The overall reactivity of both fullerenes is quite similar at te mperatures above the gasification onset of 570 K. The formation of the various adduct compounds was found to exert a detectable influence up on the overall molecular shape of the fullerenes and a small effect on the electronic structure was observed. The only moderate differences in electronic and geometric structures of pristine and initially oxidi sed fullerenes precludes a pronounced molecule-by-molecule reaction co ntrol and allows the topochemistry of the intercalation to control the shape of the reaction interface. This control is less effective for C -70 than for the C-60 fullerene.