Fullerane, the Hydrogenated C60 Fullerene: Properties and Astrochemical Considerations

Abstract

Hydrogenated C60 fullerene, C60H36 was prepared in different solvents using Zn/HCl as reducing agents. The structure of C60H36 was confirmed both by electronic and FT‐IR spectroscopy and the purity of the reaction product was checked by HPLC analysis. It has been confirmed that C60H36 is not stable in air, especially in presence of light which enhances the oxidation. The oxidation of C60H36 was studied by FT‐IR spectroscopy and by differential scanning calorimetry (DSC) in air; the formation of hydroxyl groups on the fullerene cage and ketonic groups (involving cage breakdown) have been detected. Furthermore, the action of O3 on C60H36 was investigated and it has been found that O3 exerts practically the same effect of air but causing an enhanced cage breakdown. The thermal stability of C60H36 was checked by a thermogravimetric analysis (TGA) coupled with a differential thermal analysis (DTA) under N2 flow. The vaporization of C60H36 occurs at very high temperature: the DTA trace has shown an endothermic peak at 540°C (at a heating rate of 20°C/min). C60H36 shows an electronic absorption spectrum with a maximum at about 217 nm and it is able to match both in position and in half width the peak at 217.5 nm observed in the spectrum of the interstellar extinction of light which was attributed to hydrogenated, radiation processed and thermally annealed carbon dust. Similarly, the absorption spectrum of C60H36 is able to match several infrared emission bands (called UIBs) detected from certain astrophysical objects like the protoplanetary nebulae (PPNe). It is proposed that hydrogenated fullerenes can be used as model compounds in the laboratory simulation studies of interstellar carbon dust.