Formation of Singly Bonded Fullerene Dimers in Electrospray Mass Spectrometry

The K+ adducts of the crown ether[60]fullerene conjugate of the form (12cr-4 H)-C-60-H are investigated by electrospray mass spectrometry (ESI-MS), focusing on the dimeric species produced from two different solvent mixtures. A singly bonded fullerene dimer of the type (12cr-4 H)-C-60-C-60-(12cr-4-H)(K+) is generated in aprotic solvents, while in protic solvents, a metal-bridged, noncovalently bound dimer predominates. The dimerization reaction is proposed to occur during the ESI process via the radical intermediate (12cr-4-H)C-60. The fragmentation behavior of the different dimers is studied by collision-induced dissociation (CID), showing characteristic product ions for each species.