"Umpolung" photoinduced charge separation in an anion-bound supramolecular complex

Jonathan L. Sessler, Elizabeth Karnas, Kuk Kim Sung, Zhongping Ou, Min Zhang, Karl M. Kadish, Kei Ohkubo, Shunichi Fukuzumi

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A new supramolecular system, consisting of an expanded porphyrin, cyclo[8]pyrrole (C8) and a pyrene carboxylate (Py) is capable not only of electron transfer upon photoexcitation, but results in "umpolung" or a reversal of the predicted charge-separation behavior in that the higher energy radical ion pair, C8•+-Py•- (2.58 eV) is formed as opposed to C8•--Py•+ (1.31 eV). This observation is rationalized in terms of the latter radical ion pair, C8•--Py•+ being in the Marcus inverted region. Transient absorption spectral studies reveal a charge-separated lifetime of 300 μs, which decays to the triplet state of cyclo[8]pyrrole, also an exceedingly long-lived species. The novel features of this noncovalent dyad highlight the potential utility of anion binding in the construction of supramolecular electron transfer systems.

Original languageEnglish
Pages (from-to)15256-15257
Number of pages2
JournalJournal of the American Chemical Society
Issue number46
StatePublished - 19 Nov 2008


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