Journal of Physical Chemistry B, Vol.112, No.13, 3910-3917, 2008
Effect of dual fullerenes on lifetimes of charge-separated states of subphthalocyanine-triphenylamine-fullerene molecular systems
Photoinduced intramolecular electron-transfer events of the newly synthesized subphthalocyanine-triphenylamine-fullerene triad (SubPc-TPA-C-60) and subphthalocyanine-triphenylamine-bisfullerene tetrad (SubPc-TPA-(C-60)(2)) were studied. The geometric and electronic structures of the triad were probed by ab initio B3LYP/3-21G method, which predicts SubPc-TPA(center dot+)-C-60(center dot-) as a stable charge-separated state. The photoinduced events via the excited singlet state of SubPc were monitored by time-resolved emission measurements as well as transient absorption techniques. Efficient charge-separations via the excited states of SubPc were observed with the rates of similar to 10(10) s(-1). Compared with the SubPc-TPA dyad, a long-lived charge-separated state was observed for the SubPc-TPA-C-60 triad with the lifetime of the radical ion pairs (tau(RIP)) of 670 ns in benzonitrile. Interestingly, further charge stabilization was achieved in the charge-separated state of SubPc-TPA-(C-60)(2), in which the TRIP was found to be 1050 ns in benzonitrile.