Oligosilane chain-length dependence of electron transfer of zinc porphyrin-oligosilane-fullerene molecules

Mikio Sasaki, Yuki Shibano, Hayato Tsuji, Yasuyuki Araki, Kohei Tamao, Osamu Ito

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

A new series of zinc porphyrin-fullerenes bridged by flexible oligosilane chains ZnP-[Sin]-C60 (n = 1-5) was synthesized, and the photophysical properties of these molecules were investigated using steady-state and time-resolved spectroscopic methods. The spectral observations can be well explained by assuming the coexistence of extended conformers and folded conformers, that is, the observed emissions are from the extended conformers while the folded conformers form very short lifetime nonfluorescent excited-state charge-transfer (CT) complexes. Time-resolved transient absorption spectra suggest the generation of intramolecular radical-ion pairs that have sub-microsecond lifetimes. With the number of silicon atoms of the bridged oligosilane, the lifetimes of the radical-ion pairs do not vary regularly, indicating that intramolecular collision of the radical-cation moiety with the radical-anion moiety controls the charge-recombination rate. The attenuation factor of the electron transfer of the silicon chain was evaluated by the bridge-length dependence of charge-separation rate to be 0.16 Å-1 on the basis of the oligosilane chain-length dependence of fluorescence lifetimes. This is the first evaluation of the attenuation factor for the one-dimensional Si-Si chain to the best of our knowledge.

Original languageEnglish
Pages (from-to)2973-2979
Number of pages7
JournalJournal of Physical Chemistry A
Volume111
Issue number16
DOIs
Publication statusPublished - 2007 Apr 26

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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