Electron transfer and multi-electron accumulation in ExBox4+

Scott M. Dyar, Jonathan C. Barnes, Michal Juríček, J. Fraser Stoddart, Dick T. Co, Ryan M. Young, Michael R. Wasielewski

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Molecules capable of accepting and storing multiple electrons are crucial components of artificial photosynthetic systems designed to drive catalysts, such as those used to reduce protons to hydrogen. ExBox4+, a boxlike cyclophane comprising two π-electron-poor extended viologen units tethered at both ends by two p-xylylene linkers, has been shown previously to accept an electron through space from a photoexcited guest. Herein is an investigation of an alternate, through-bond intramolecular electron-transfer pathway involving ExBox4+ using a combination of transient absorption and femtosecond stimulated Raman spectroscopy (FSRS). Upon photoexcitation of ExBox 4+, an electron is transferred from one of the p-xylylene linkers to one of the extended viologen units in ca. 240 ps and recombines in ca. 4 ns. A crystal structure of the doubly reduced species ExBox2+ was obtained. From outside the box: A viologen-based cyclophane ExBox4+ is photoexcited revealing a new through-bond pathway for electron transfer to ExBox4+. The solid-state structure with both redox states ExBox 4+ and ExBox2+ present, confirms that transferred electrons cause ExBox2+ to become flattened and form semiquinoidal structures capable of stabilizing unpaired electrons.

Original languageEnglish (US)
Pages (from-to)5371-5375
Number of pages5
JournalAngewandte Chemie - International Edition
Issue number21
StatePublished - May 19 2014


  • ExBox
  • cyclophanes
  • electron transfer
  • femtochemistry
  • photochemistry

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis


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