Ultrafast photoinduced electron transfer in a chlorophyll-based triad: Vibrationally hot ion pair intermediates and dynamic solvent effects

Gary P. Wiederrecht, Mark P. Niemczyk, Walter A. Svec, Michael R. Wasielewski

Research output: Contribution to journalArticle

119 Citations (Scopus)

Abstract

We report ultrafast transient absorption studies of photoinduced electron transfer in the triad molecule zinc methyl 131-desoxopyropheophorbide a - pyromellitimide - 1,8:4,5-naphthalenediimide (ZC-PI-NI) in solution. The absorption spectra of the radical anions of PI and NI possess narrow and well-separated absorption bands which permit the direct observation of both the intermediate and final charge-separated states. Selective optical excitation of the ZC donor results in the formation of the intermediate charge-separated state, ZC+-PI--NI, in less than 2 ps in nonpolar solvents. The PI radical ion within the ZC+-PI--NI intermediate is vibrationally excited as illustrated by time-dependent changes in the band shape of its transient absorption spectrum. The rate of the initial charge separation reaction forming ZC+-PI--NI and the subsequent charge shift reaction to form the final state, ZC+-PI-NI-, as well as the appearance of the vibrationally excited intermediate are all highly solvent dependent even for solvents with similar dielectric constants. Analogous dyad control molecules ZCPI and ZCNI were also studied and compared with the results for ZCPINI.

Original languageEnglish
Pages (from-to)81-88
Number of pages8
JournalJournal of the American Chemical Society
Volume118
Issue number1
DOIs
Publication statusPublished - Jan 10 1996

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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