Intramolecular photoinduced electron-transfer processes in buta-1,3-diynyl-benzene-linked porphyrin-fullerene dyad

Intramolecular electron-transfer process of porphyrin-fullerene dyad linked by phenyl buta-1,3-diynyl-phenyl unit ( ZnP - sp - C 60 ) was studied by laser flash photolysis. Picosecond fluorescence lifetime and transient absorption measurements revealed that photoinduced charge-separation takes place via the excited singlet state ( 1 ZnP *) with the rate constant of (1-2) × 10 10 s −1 . For the charge recombination, about a half of the radical-ion pair decayed quickly with 2.9 × 10 9 s −1 as evaluated from picosecond transient absorption measurements, whereas the remaining half was long-lived with slow decay (1.6 × 10 6 s −1 ) as estimated from nanosecond transient absorption measurements. The lifetime of the radical-ion pair of ZnP - sp - C 60 was longer than those of directly connected dyads with a buta-1,3-diynyl bridge and buta-1,3-diynyl-phenyl bridge by the insertion of an extra phenyl group in addition to the pyrrodino ring.