| Abstract
| - Nonconjugated dendrimers, which are capable of funneling energy from the periphery to thecore followed by a charge-transfer process from the core to the periphery, have been synthesized. Theenergy and electron donors involve a diarylaminopyrene unit and are incorporated at the periphery of thesedendrimers. The energy and electron acceptor is at the core of the dendrimer, which involves a chromophorebased on a benzthiadiazole moiety. The backbone of the dendrimers is benzyl ether based. A direct electron-transfer quenching of the excited state of the periphery or a sequential energy transfer−electron-transferpathway are the two limiting mechanisms of the observed photophysical properties. We find that the lattermechanism is prevalent in these dendrimers. The energy transfer occurs on a picosecond time scale,while the charge-transfer process occurs on a nanosecond time scale. The lifetime of the charge separatedspecies was found to be in the range of microseconds. Energy transfer efficiencies ranging from 80% to90% were determined using both steady-state and time-resolved measurements, while charge-transferefficiencies ranging from 70% to 80% were deduced from fluorescence quenching of the core chromophore.The dependence of the energy and charge-transfer processes on dendrimer generation is analyzed interms of the backfolding of the flexible benzyl ether backbone, which leads to a weaker dependence of theenergy and charge-transfer efficiencies on dendrimer size than would be expected for a rigid system.
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