Stable Organic (Bi)Radicals by Delocalization of Spin Density into the Electron-Poor Chromophore Core of Isoindigo

Rodger Rausch, David Schmidt, David Bialas, Ivo Krummenacher, Holger Braunschweig, Frank Würthner

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The first isoindigo (bi)radicals were obtained by proton coupled oxidation of their 4-hydroxyaryl substituted precursors. Optical and magnetic spectroscopic studies revealed a singlet open-shell biradicaloid electronic ground state for the bisphenoxyl-isoindigo (<s2>=1.20) with a small singlet–triplet energy gap of 0.065 eV and a large biradical character of y=0.79 that was corroborated by temperature-dependent EPR spectroscopy and quantum chemical calculations. The concept of kinetic blocking of the radical centers and delocalization of spin density into the electron-withdrawing chromophore core of isoindigo offers an entry into a new class of exceptionally stable open-shell functional materials based on organic colorants.

Original languageEnglish (US)
Pages (from-to)3420-3424
Number of pages5
JournalChemistry - A European Journal
Issue number14
StatePublished - Mar 7 2018

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry

Cite this