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 (MLCT)-M-1 transition, the formed (MLCT)-M-3 state is readily quenched in the presence of C-60. The photoinduced dynamics have been studied by transient absorption spectroscopy, which reveals fast depopulation of the (MLCT)-M-3 (73-406 ps). As a consequence, energy transfer occurs, populating a long-lived triplet state, which could be assigned to the C-3(60)* state.