Building Carbon Bridges on and between Fullerenes in Helium Nanodroplets

Abstract

We report the observation of sequential encounters of fullerenes with C atoms in an extremely cold environment. Experiments were performed with helium droplets at 0.37 K doped with C ₆₀ molecules and C atoms derived from a novel, pure source of C atoms. Very high-resolution mass spectra revealed the formation of carbenes of the type C ₆₀(C:) _n with n up to 6. Bridge-type bonding of the C adatoms to form the known dumbbell C ₆₀=C=C ₆₀ also was observed. Density functional theory calculations were performed that elucidated the carbene character of the C ₆₀(C:) _n species and their structures. Mass spectra taken in the presence of water impurities and in separate experiments with added H ₂ also revealed the formation of the adducts C ₆₀C _n (H ₂O) _n and C ₆₀C _n (H ₂) _n probably by H–OH and H–H bond insertion, respectively, and nonreactivity for the dumbell. So C adatoms that form carbenes C ₆₀(C:) _n can endow pristine C ₆₀ with a higher chemical reactivity.