An Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Study of 1,6-Methano[60]Fullerene-61,61-Dicarboxylic Acid

1,6-Methano[60]fullerene-61,61-dicarboxylic acid was studied by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The deprotonated molecule, C₆₀C(COOH)COO⁻, and the decarboxylated molecular anion C₆₀CHCOO⁻ were observed. Gas-phase ion–molecule reactions occurred when the ion accumulation time in an external rf/dc hexapole ion trap was extended. Cluster ions of the type [C₆₀CHCOOH] _n [C₆₀CHCOO]⁻ (n = 1–2) were observed. Multiply-charged anions were observed for the dimer [C₆₀CHCOOH][C₆₀CHCOO]⁻. Collision-induced dissociation in the ion cyclotron resonance cell showed that C₆₀C(COOH)COO⁻ dissociated through the loss of two CO₂ groups, with further fragmentation to produce C₆₀⁻. A similar fragmentation pathway was also observed with capillary/skimmer collision-induced dissociation during the electrospray process. Semi-empirical calculations using the AM1 approximation with the MOPAC program have been performed on most of the neutral and ionic species related to this compound. Energy differences and charge distributions have been obtained for the possible geometry structures for these species.