Experimental study of reactions of the buckminsterfullerene cations C60.bul.+, C602+, and C60.bul.3+ with ammonia and amines in the gas phase

Abstract

Results of SIFT experiments are reported for ion-molecule reactions initated by C[sub 60][sup [center dot]+], C[sub 60][sup 2+], C[sub 60][sup [center dot]3+] in ammonia, methylamine, ethylamine, 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 transfer 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. Addition is the only primary product channel observed with C[sub 60][sup [center dot]+]. The apparent bimolecular rate coefficient for adduct formation increases systematically from a low value of less than 1 [times] 10[sup [minus]12] cm[sup 3] molecule[sup [minus]1] s[sup [minus]1] (with NH[sub 3]) to a value which appears to saturate at about 1 [times] 10[sup [minus]9] cm[sup 3] molecule[sup [minus]1] s[sup [minus]1], the collision rate coefficient, with decreasing ionization energy of the added amine. C-N bond formation is proposed for these addition reactions and a model is presented which accounts for the trend in the rate coefficients. Secondary adducts were observed to form rapidly with ammonia andmore » all of the amines except trimethylamine and are attributed to the formation of a proton bond. Charge transfer was observed to compete with addition in the reactions of the C[sub 60][sup 2+] dication with the amines (NH[sub 3] reacted exclusively by addition), increasing in relative importance with decreasing ionization energy of the amine. 31 refs., 5 figs., 3 tabs.« less