Mechanism of Back Electron Transfer in an Intermolecular Photoinduced Electron Transfer Reaction: Solvent as a Charge Mediator

Sudhakar Narra, Yoshifumi Nishimura, Henryk A. Witek, Shinsuke Shigeto

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Back electron transfer (BET) is one of the important processes that govern the decay of generated ion pairs in intermolecular photoinduced electron transfer reactions. Unfortunately, a detailed mechanism of BET reactions remains largely unknown in spite of their importance for the development of molecular photovoltaic structures. Here, we examine the BET reaction of pyrene (Py) and 1,4-dicyanobenzene (DCB) in acetonitrile (ACN) by using time-resolved near- and mid-IR spectroscopy. The Py dimer radical cation (Py2 .+) and DCB radical anion (DCB.-) generated after photoexcitation of Py show asynchronous decay kinetics. To account for this observation, we propose a reaction mechanism that involves electron transfer from DCB.- to the solvent and charge recombination between the resulting ACN dimer anion and Py2 .+. The unique role of ACN as a charge mediator revealed herein could have implications for strategies that retard charge recombination in dye-sensitized solar cells.

Original languageEnglish
Pages (from-to)2945-2950
Number of pages6
JournalChemPhysChem
Volume15
Issue number14
DOIs
Publication statusPublished - 2014 Oct 1
Externally publishedYes

Keywords

  • charge recombination
  • electrons
  • ion pairs
  • photochemistry
  • time-resolved spectroscopy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry

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