Upon light irradiation, a tetraketosulfoxide
derivative of C60 was transformed into a diketosulfide
carboxylic anhydride
via intermolecular nucleophilic addition of the sulfoxide moiety.
The thus-formed 18-membered ring enables a spontaneous insertion of
an Ar atom. In this encapsulation/release process, the phenyl ring
on the orifice works as a dynamic stopper, which potentially adopts
three conformations: an open form reduces distortion energy at the
transition state while semiopen and closed forms reduce the orifice
size.