Synthesis and Thin Films of Thermally Robust Quartet (S = 3/2) Ground State Triradical

Chan Shu, Maren Pink, Tobias Junghoefer, Elke Nadler, Suchada Rajca, Maria Benedetta Casu, Andrzej Rajca

Research output: Contribution to journalArticlepeer-review

Abstract

High-spin (S = 3/2) organic triradicals may offer enhanced properties with respect to several emerging technologies, but those synthesized to date typically exhibit small doublet quartet energy gaps and/or possess limited thermal stability and processability. We report a quartet ground state triradical 3, synthesized by a Pd(0)-catalyzed radical-radical cross-coupling reaction, which possesses two doublet-quartet energy gaps, ΔEDQ ≈ 0.2-0.3 kcal mol-1 and ΔEDQ2 ≈ 1.2-1.8 kcal mol-1. The triradical has a 70+% population of the quartet ground state at room temperature and good thermal stability with onset of decomposition at >160 °C under an inert atmosphere. Magnetic properties of 3 are characterized by SQUID magnetometry in polystyrene glass and by quantitative EPR spectroscopy. Triradical 3 is evaporated under ultrahigh vacuum to form thin films of intact triradicals on silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy. AFM and SEM images of the μ1 nm thick films indicate that the triradical molecules form islands on the substrate. The films are stable under ultrahigh vacuum for at least 17 h but show onset of decomposition after 4 h at ambient conditions. The drop-cast films are less prone to degradation in air and have a longer lifetime.

Original languageEnglish (US)
Pages (from-to)5508-5518
Number of pages11
JournalJournal of the American Chemical Society
Volume143
Issue number14
DOIs
StatePublished - Apr 14 2021

ASJC Scopus subject areas

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

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