Isomer-Specific Trends with Charge State in Gas-Phase Reactions of Fullerene Cations, C₆₀x⁺ (x = 1−3), with Nitromethane and Methyl Nitrite:  Polymethoxylation of C₆₀ Dications

Rate coefficients and product distributions have been measured for the gas-phase reactions of C 60 • +, C 60 2+, and C 60 • 3+ with nitromethane and methyl nitrite which show a strong dependence of reactivity on the charge state of the fullerene cation and on the nature of the neutral reactant isomer. Furthermore, sequential bimolecular methoxy-radical transfer reactions were observed with methyl nitrite leading to the polymethoxylation of C 60 2+ with up to 12 methoxy groups, far more than the number of charges on the C 60 surface. Unusual periodicities were seen in the reaction kinetics, and these are correlated with the radical and aromatic character of the derivatized C 60 (OCH 3 ) n 2+ cations. The measurements were performed in helium buffer gas at 0.35 ± 0.01 Torr and 294 ± 3 K with use of the Selected-Ion Flow Tube (SIFT) technique. Multicollision induced dissociation experiments with the derivatized C 60 (OCH 3 ) n 2+ ( n = 1−4) cations indicated sequential loss of single methoxy radicals, which is consistent with direct bonding of the methoxy groups to the C 60 cage. Polymethoxylation was not observed with C 60 • 3+ . Instead, C 60 • 3+ reacts with methyl nitrite by dissociative electron transfer. C 60 2+ is unreactive with nitromethane, but C 60 • 3+ adds one molecule and the C 60 (CH 3 NO 2 ) • 3+ adduct ion reacts further only by proton transfer. C 60 • + is unreactive with both nitromethane and methyl nitrite.