Organic spin clusters: Macrocyclic-macrocyclic polyarylmethyl polyradicals with very high spin S = 5-13

Andrzej Rajca, Jirawat Wongsriratanakul, Suchada Rajca

Research output: Contribution to journalArticle

74 Scopus citations

Abstract

Synthesis and magnetic studies of a new class of organic spin clusters, possessing alternating connectivity of unequal spins, are described. Polyarylmethyl polyether precursors to the spin clusters, with linear and branched connectivity between calix[4]arene-based macrocycles, are prepared via modular, multistep syntheses. Their molecular connectivity and stereoisomerism are analyzed using NMR spectroscopy. The absolute masses (4-10 kDa) are determined by FABMS and GPC/MALS. Small angle neutron scattering (SANS) provides the radii of gyration of 1.2-1.8 nm. The corresponding polyradicals with 15, 22, and 36 triarylmethyls, which are prepared and studied as solutions in tetrahydrofuran-d8, may be described as S′ = 7/2, 1/2, 7/2 spin trimer (average S = 5-6), S′ = 7/2, 1/2, 6/2, 1/2, 7/2 spin pentamer (average S = 7-9), and spin nonamer (average S = 11-13), respectively, as determined by SQUID magnetometry and numerical fits to linear combinations of the Brillouin functions. For spin trimer and pentamer, the quantitative magnetization data are fit to new percolation models, based upon random distributions of chemical defects and ferromagnetic vs antiferromagnetic couplings. The value of S = 13 is the highest for an organic molecule.

Original languageEnglish (US)
Pages (from-to)6608-6626
Number of pages19
JournalJournal of the American Chemical Society
Volume126
Issue number21
DOIs
StatePublished - Jun 2 2004

ASJC Scopus subject areas

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

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