Probing charge transfer in benzodifuran-C₆₀ dumbbell-type electron donor-acceptor conjugates: Ground- and excited-state assays

Rigid electron donor-acceptor conjugates (1-3) that combine π-extended benzodifurans as electron donors and C₆₀ molecules as electron acceptors with different linkers have been synthesized and investigated with respect to intramolecular charge-transfer events. Electrochemistry, fluorescence, and transient absorption measurements revealed tunable and structure-dependent charge-transfer processes in the ground and excited states. Our experimental findings are underpinned by density-functional theory calculations. Dumbbell arrays: A benzodifuran (BDF) donor is for the first time fused to two C₆₀ molecules by different linkers to form triads 1-3 (see figure). Their redox behavior, absorption, fluorescence emission, and photoinduced intramolecular charge-transfer events have been investigated experimentally and theoretically. The lifetime of the resulting charge-separated state varies distinctly with the polarity of the solvents and the distance between the BDF and C₆₀ units.