Photoinduced electron-transfer processes of a newly synthesized rotaxane containing porphyrinatozinc (ZnP), fullerene (C60), and ferrocene (Fc) have been studied in terms of the time-resolved fluorescence and transient absorption measurements in polar and nonpolar solvents. In this rotaxane, (ZnP;C60-Fc)rotax, ZnP was chosen as a pendant of a crown-ether necklace, through which an axle with C60 and Fc at both termini was penetrated. By the selective excitation of the ZnP moiety in a nonpolar solvent, energy transfer predominantly takes place to the C 60 moiety of (ZnP;C60-Fc)rotax. In polar solvents, charge-separation process takes place via the excited singlet state of the ZnP moiety in addition to the energy-transfer process. From the nanosecond transient absorption spectra, a clear absorption band of the C60 •- moiety was observed at 1000 nm as well as a broad absorption in the 600-800 nm region due to ZnP•+, suggesting the generation of (ZnP•+;C60•--Fc)rotax in the first step. Afterward, the hole-transferring process from ZnP •+ to Fc is thermodynamically possible, although this process is not fast because of its through-space process character. The final lifetimes of the C60•- moiety were evaluated to be 290 and 370 ns in benzonitrile and DMF, respectively. The ratios of the charge-separation rates to charge-recombination rates were ca. 1000, indicating that (ZnP;C 60-Fc)rotax affords an efficient photosynthetic model.
|Number of pages||11|
|Journal||Journal of Porphyrins and Phthalocyanines|
|Publication status||Published - 2005 Jan 1|
- Photoinduced electron transfer
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