Redox states of long oligothiophenes: Two polarons on a single chain

John A.E.H. Van Haare, Edsko E. Havinga, Joost L.J. Van Dongen, René A.J. Janssen*, Jérôme Cornil, Jean-Luc Bredas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

243 Scopus citations

Abstract

A detailed investigation is presented of the redox states of three oligothiophenes (nT) with 6, 9, and 12 thiophene units. While open-shell radical cations (polarons) and closed-shell dications (bipolarons) are usually invoked as the primary redox species in these systems, we have obtained evidence that the dication of the longest oligothiophene (12T) has an electronic structure with two individual polarons. The redox states of 6T, 9T, and 12T have been fully characterized using UV/visible/near-IR and ESR spectroscopy in combination with electrospray mass spectrometry. For 6T and 9T, single-electron oxidation in dichloromethane produces the corresponding radical cations, which form spinless π dimers at lower temperatures. A second oxidation step forms dications which possess a bipolaronic electronic structure. However, the redox behavior of the longest oligothiophene, 12T, is entirely different. Radical cations of 12T disproportionate into neutral oligomers and dications, except at the lowest oxidation levels. The spectral data for doubly oxidized 12T are incompatible with those expected for a bipolaronic structure but are consistent with the formation of two individual polarons on a single chain; this interpretation is also supported by the results from correlated quantum chemical calculations.

Original languageEnglish (US)
Pages (from-to)1509-1522
Number of pages14
JournalChemistry - A European Journal
Volume4
Issue number8
DOIs
StatePublished - Jan 1 1998

Keywords

  • Conducting materials
  • Oligomers
  • Pi interactions
  • Radical ions
  • Redox chemistry

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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