EXPERIMENTAL-STUDY OF REACTIONS OF THE BUCKMINSTERFULLERENE CATIONS C-60(.-60(2+), AND C-60(.3+) WITH AMMONIA AND AMINES IN THE GAS-PHASE(), C)

Results of SIFT experiments are reported for ion-molecule reactions in itiated by C60.+, C60(2+), and C60(.3+) in ammonia, methylamine, ethyl amine, dimethylamine, and trimethylamine at 294 +/- 2 K in helium gas at a pressure of 0.35 +/- 0.02 Torr. The main features of the observed reactions can be described in terms of adduct formation and charge tr ansfer and are in line with the known electron recombination energies of these three fullerene cations. Higher order reactions of the adduct ions display both further adduct formation and proton transfer. Addit ion is the only primary product channel observed with C60.+. The appar ent bimolecular rate coefficient for adduct formation increases system atically from a low value of less than 1 X 10(-12) cm3 molecule-1 s-1 (with NH3) to a value which appears to saturate at about 1 x 10(-9) cm 3 molecule-1 s-1, the collision rate coefficient, with decreasing ioni zation energy of the added amine. C-N bond formation is proposed for t hese addition reactions and a model is presented which accounts for th e trend in the rate coefficients. Secondary adducts were observed to f orm rapidly with ammonia and all of the amines except trimethylamine a nd are attributed to the formation of a proton bond. Charge transfer w as observed to compete with addition in the reactions of the C60(2+) d ication with the amines (NH3 reacted exclusively by addition), increas ing in relative importance with decreasing ionization energy of the am ine. Secondary adduct formation, although observed with ammonia, methy lamine, and ethylamine, was seen to occur in competition with a domina nt proton-transfer channel. Addition of up to three molecules of ammon ia was observed with C60(.3+), with each adduct also undergoing proton transfer in a secondary reaction with ammonia. The amines react with C60(.3+) exclusively by charge transfer which in the case of ethylamin e is largely dissociative. It is proposed that the reactions of C60.and C60(2+) provide pathways for nitrogen derivatization of neutral fu llerenes in the presence of ionization sources and mechanisms for ion neutralization, as, for example, in interstellar clouds and circumstel lar envelopes.