Challenges in distinguishing superexchange and hopping mechanisms of intramolecular charge transfer through fluorene oligomers

Randall H. Goldsmith, Orlando DeLeon, Thea M. Wilson, Daniel Finkelstein-Shapiro, Mark A. Ratner, Michael R. Wasielewski

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Abstract

The temperature dependence of intramolecular charge separation in a series of donor-bridge-acceptor molecules having phenothiazine (PTZ) donors, 2,7-oligofluorene FLn (n = 1-4) bridges, and perylene-3,4:9,10- bis(dicarboximide) (PDI) acceptors was studied. Photoexcitation of PDI to its lowest excited singlet state results in oxidation of PTZ via the FLn bridge. In toluene, the temperature dependence of the charge separation rate constants for PTZ-FLn-PDI, (n = 1-4) is relatively weak and is successfully described by the semiclassical Marcus equation. The activation energies for charge separation suggest that bridge charge carrier injection is not the rate limiting step. The difficulty of using temperature and length dependence to differentiate hopping and superexchange is discussed, with difficulties in the latter topic explored via an extension of a kinetic model proposed by Bixon and Jortner.

Original languageEnglish
Pages (from-to)4410-4414
Number of pages5
JournalJournal of Physical Chemistry A
Volume112
Issue number19
DOIs
Publication statusPublished - May 15 2008

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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