Time-resolved X-ray absorption determination of structural changes following photoinduced electron transfer within bis-porphyrin heme protein models

Lin X. Chen, Peter L. Lee, David Gosztola, Walter A. Svec, Pedro A. Montano, Michael R. Wasielewski

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Time domain energy dispersive X-ray absorption spectroscopy provides a powerful probe of changes in molecular structure that occur during photoinduced electron transfer reactions. In this study a diporphyrin model for electron transfer within modified heme proteins is examined using this technique. Transient optical absorption experiments show that photoinduced electron transfer from the lowest excited triplet state of a Zn porphyrin attached at a fixed 25 Å distance by means of a long spacer molecule to an Fe(III) porphyrin occurs with a 6 ms time constant at 77 K. Time domain X-ray absorption measurements are consistent with transient reduction of Fe(III) to Fe(II) that is accompanied by substantial weakening of the bond between the Fe atom and a pyridine molecule ligated to it. Coupling of ligand loss to reduction of Fe(III) to Fe(II) provides a means of stabilizing the reduced intermediate.

Original languageEnglish
Pages (from-to)3270-3274
Number of pages5
JournalJournal of Physical Chemistry B
Issue number16
Publication statusPublished - Dec 1 1999


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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