New ruthenium bis(terpyridine) methanofullerene and pyrrolidinofullerene complexes: synthesis and electrochemical and photophysical properties.

A series of terpyridine (tpy) methanofullerene and pyrrolidinofullerene dyads linked via p-phenylene or p-phenyleneethynylenephenylene (PEP) units is presented. The coordination to ruthenium(II) yields donor-bridge-acceptor assemblies with different lengths. Cyclic voltammetry and UV-vis and luminescence spectroscopy are applied to study the electronic interactions between the active moieties. It is shown that, upon light excitation of the ruthenium(II)-based (1)MLCT transition, the formed (3)MLCT state is readily quenched in the presence of C60. The photoinduced dynamics have been studied by transient absorption spectroscopy, which reveals fast depopulation of the (3)MLCT (73-406 ps). As a consequence, energy transfer occurs, populating a long-lived triplet state, which could be assigned to the (3)C60* state.