Isolation and crystal structures of two singlet bis(triarylamine) dications with nonquinoidal geometries

Shijun Zheng, Stephen Barlow, Chad Risko, Tiffany L. Kinnibrugh, Viktor N. Khrustalev, Simon C. Jones, Mikhail Yu Antipin, Neil M. Tucker, Tatiana V. Timofeeva, Veaceslav Coropceanu, Jean Luc Brédas, Seth R. Marder

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

We report the first structural data for bis(diarylamine) "bipolarons": we have isolated and crystallographically characterized salts of the dications obtained by two-electron oxidation of E-4,4′-bis-[di(p-anisyl)amino]stilbene and E,E-2,5-bis{4-[di(p-anisyl) amino]styryl}-3,4-di(n-butoxy)thiophene, [1]2+ and [2]2+ respectively. ESR, NMR, and magnetometry suggest both species have singlet ground states. X-ray structures, together with 1H NMR coupling constants for [2]2+, indicate geometries in which the bond lengths are shifted toward a quinoidal pattern relative to that in the neutral species, but not to a fully quinoidal extent. In particular, the bond-length alternations across the vinylene bridging groups approach zero. DFT calculations with closed-shell singlet configurations reproduce the observed structures well. Our results indicate that singlet species for which one might expect quinoidal geometries (with differences of ca. 0.1 Å between formally single and double bonds) on the basis of a limiting valence-bond representation of the structure can, in fact, show structures with significantly different patterns of bond lengths.

Original languageEnglish (US)
Pages (from-to)1812-1817
Number of pages6
JournalJournal of the American Chemical Society
Volume128
Issue number6
DOIs
StatePublished - Feb 15 2006
Externally publishedYes

ASJC Scopus subject areas

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

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