Tuning charge transfer energetics in reaction center mimics via T(h)-functionalization of fullerenes

We have introduced an approach of mono- and hexakis-adducts of C(60) involving a T(h)-symmetrical addition pattern, where up to 12 ferrocene or 10 ferrocene and one porphyrin units are linked flexibly to C(60) with the objective to systematically raise the energy of the radical ion pair state. A detailed electrochemical and photophysical investigation has shed light onto charge transfer events that depend largely on (i) the functionalization pattern of C(60), (ii) the donor strength of the donor, (iii) the excited-state energy of the predominant chromophore, and (iv) the solvent polarity. Considering (i)-(iv), the presence of the porphyrins is key to providing sufficient driving forces for affording spatially separated radical ion pair states. An ideal scenario, that is, testing ZnP-C(60)-(Fc)(10) (19) in benzonitrile and DMF, allows storing nearly 1.7 eV in a nanosecond lived radical ion pair state. In this context, the flexible linkage, powering a through space charge transfer, prevents, however, stabilization of the radical ion pair state beyond nanoseconds.