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 fluores- cence lifetime And transient absorption measurements revealed that photoinduced charge-separation takes place via the excited singlet state ('ZnP*) with the rate constant of (1-2) x 10(10) s(-1). For the charge recombination, about a half of the radical-ion pair decayed quickly with 2.9 x 10(9) s(-1) as evaluated from picosecond transient absorption measurements, whereas the remaining half was long-lived with slow 106 decay (1.6 x 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. Copyright (C) 2007 Society of Porphyrins & Phthalocyanines.