Building Carbon Bridges on and between Fullerenes in Helium Nanodroplets

[Image: see text] 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(60)C(n)(H(2)O)(n) and C(60)C(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.