C70vs. C60 in zinc porphyrin—fullerene dyads: prolonged charge separation and ultrafast energy transfer from the second excited singlet state of porphyrin

The second excited singlet (S2) state of porphyrin was efficiently quenched by the attached fullerene C70 moiety in a zinc porphyrin–C70 dyad. The quenching is largely explained by energy transfer to C70, but the possibility of additional reactions involving the S2 state of porphyrin is discussed. Singlet energy transfer was found to be an important decay pathway also for the first excited singlet (S1) state of porphyrin. In the polar solvent benzonitrile a charge-separated state was formed, and its lifetime was 890 ps, 50% longer than in the analogous porphyrin–C60 dyad.