An extremely long-lived charge-separated state of zinc tetraphenylporphyrin coordinated with pyridylnaphthalene-diimide

Kenji Saito, Yukiyasu Kashiwagi, Kei Ohkubo, Shunichi Fukuzumi

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The nitrogen of pyridylnaphthalenediimide (PyNIm) coordinates to the metal center of zinc tetraphenylporphyrin (ZnTPP) to form a donor-acceptor complex: ZnTPP-PyNIm. Formation of the ZnTPP-PyNIm complex was probed by UV-vis, fluorescence and NMR spectra. The fluorescence of ZnTPP is strongly quenched and the fluorescence lifetime is shortened significantly in the complex. The transient absorption spectrum of the charge-separated state (ZnTPP •+-PyNIm•-) is successfully detected by laser flash photolysis measurements of the ZnTPP-PyNIm system in benzonitrile. The charge-separated state of the complex produced by the photoinduced electron transfer has the longest lifetime, (450 μs) at 288 K, ever reported for donor-acceptor systems linked covalently or non-covalently in solution. However, when benzonitrile is replaced by benzene, the triplet excited state ( 3ZnTPP*), rather than the charge-separated state, is formed upon laser excitation of the ZnTPP-PyNIm complex, due to the lower energy of 3ZnTPP* compared to the charge-separated state in benzene.

Original languageEnglish
Pages (from-to)1371-1379
Number of pages9
JournalJournal of Porphyrins and Phthalocyanines
Issue number12
StatePublished - 2006


  • Charge separation
  • Donor-acceptor complex
  • Photoinduced electron transfer
  • Zinc porphyrin


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