Versatile bisethynyl[60]fulleropyrrolidine scaffolds for mimicking artificial light-harvesting photoreaction centers

Fullerene-based tetrads, triads, and dyads are presented in which [60]fulleropyrrolidine synthons are linked to an oligo(p-phenyleneethynylene) antenna at the nitrogen atom and to electron-donor phenothiazine (PTZ) and/or ferrocene (Fc) moieties at the α carbon of the pyrrolidine cycle through an acetylene spacer. Cyclic voltammetry and UV/ Vis absorption spectra evidence negligible ground-state electronic interactions among the subunits. By contrast, strong excited-state interactions are detected upon selective light irradiation of the antenna (UV) or of the fullerene scaffold (Vis). When only PTZ is present as electron donor, photoinduced electron transfer to the fullerene unit is unambiguously detected in benzonitrile, but this is not the case when Fc is part of the multicomponent system. These results suggest that Fc is a formidable energy transfer quencher and caution should be used in choosing it as electron donor to promote efficient charge separation in multicomponent arrays.