The structure of C 60Mu and other fullerenyl radicals

Abstract

The structures of the radicals exo-C 60Mu, endo-C 60Mu, and (Mu@C 60) are discussed, with particular reference to the spin distribution of the unpaired electron in the most stable isomer (exo). The magnitude of the measured muon hyperfine interaction indicates partial spin delocalization in this radical. This is supported by semi-empirical calculations on C 60H. Calculations also show that there is a significant energy barrier between the endo radical and (Mu@C 60), supporting the assignment of the pseudo-free muonium signal to the latter structure.