X-ray crystallography and magnetic studies of a stable macrocyclic tetranitroxide. Intramolecular dimer of nitroxides in a constrained geometry of the upper rim of calix[4]arene

Andrzej Rajca, Maren Pink, Teerapat Rojsajjakul, Kan Lu, Hua Wang, Suchada Rajcat

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

Synthesis, crystallography, and magnetic characterization of a stable macrocyclic tetranitroxide 1, a calix[4]arene, which is functionalized with four tert-butylnitroxides at the upper rim, is described. In solution, 1 has a 4-fold symmetric fixed cone conformation on the NMR time scale and small, but nonnegligible, exchange interactions between the radicals (30 K > |J/k| ≫ 1.8 mK). In the solid state, dimerization of one diagonal pair of nitroxides leads to a pinched cone conformation for 1 with strong intradimer antiferromagnetic coupling with |J/k| = 200-300 K (singlet-triplet energy gap, ΔEST ≈ 1 kcal/mol).

Original languageEnglish (US)
Pages (from-to)8534-8538
Number of pages5
JournalJournal of the American Chemical Society
Volume125
Issue number28
DOIs
StatePublished - Jul 16 2003

ASJC Scopus subject areas

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

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