Axially Substituted Silicon Phthalocyanine as Electron Donor in a Dyad and Triad with Azafullerene as Electron Acceptor for Photoinduced Charge Separation.

The synthesis of a donor-acceptor silicon phthalocyanine (SiPc)-azafullerene (C59 N) dyad 1 and of the first acceptor-donor-acceptor C59 N-SiPc-C59 N dumbbell triad 2 was accomplished. The two C59 N-based materials were comprehensively characterized with the aid of NMR spectroscopy, MALDI-MS as well as DFT calculations and their redox and photophysical properties were evaluated with CV and steady-state and time-resolved absorption and photoluminescence spectroscopy measurements. Notably, femtosecond transient absorption spectroscopy assays revealed that both dyad 1 and triad 2 undergo, after selective photoexcitation of the SiPc moiety, photoinduced electron transfer from the singlet excited state of the SiPc moiety to the azafullerene counterpart to produce the charge-separated state, with lifetimes of 660 ps, in the case of dyad 1, and 810 ps, in the case of triad 2. The current results are expected to have significant implications en route to the design of advanced C59 N-based donor-acceptor systems targeting energy conversion applications.