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

J Am Chem Soc. 2008 Nov 19;130(46):15256-7. doi: 10.1021/ja806813x. Epub 2008 Oct 25.

Abstract

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 micros, 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anions / chemistry
  • Models, Chemical*
  • Molecular Structure
  • Organic Chemicals / chemistry*
  • Photochemistry
  • Spectrophotometry

Substances

  • Anions
  • Organic Chemicals