Formation of Ground State Triplet Diradicals from Annulated Rosarin Derivatives by Triprotonation

Shunichi Fukuzumi, Kei Ohkubo, Masatoshi Ishida, Christian Preihs, Bo Chen, Weston Thatcher Borden, Dongho Kim, Jonathan L. Sessler

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


Annulated rosarins, β,β′-bridged hexaphyrin( derivatives 1-3, are formally 24 π-electron antiaromatic species. At low temperature, rosarins 2 and 3 are readily triprotonated in the presence of trifluoroacetic acid in dichloromethane to produce ground state triplet diradicals, as inferred from electron paramagnetic resonance (EPR) spectral studies. From an analysis of the fine structure in the EPR spectrum of triprotonated rosarin H333+, a distance of 3.6 Å between the two unpaired electrons was estimated. The temperature dependence of the singlet-triplet equilibrium was determined by means of an EPR titration. Support for these experimental findings came from calculations carried out at the (U)B3LYP/6-31G∗ level, which served to predict a very low-lying triplet state for the triprotonated form of a simplified model system 1.

Original languageEnglish
Pages (from-to)9780-9783
Number of pages4
JournalJournal of the American Chemical Society
Issue number31
Publication statusPublished - 2015 Aug 12

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

All Science Journal Classification (ASJC) codes

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


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