Semiempirical investigation of stilbene-linked diradicals and magnetic study of their bis(N-tert-butylnitroxide) variants

Naoki Yoshioka, Paul M. Lahti, Takashi Kaneko, Yoshihiro Kuzumaki, Eishun Tsuchida, Hiroyuki Nishide

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The electronic states of open-shell stilbene diradicals were studied. Previously used semiempirical MO-CI methods were applied to stilbenes having dimethylene, dioxyl, and dinitroxide centers in o,o′-, o,m′-, o,p′-, m,m′-, m,p′-, and p,p′-substitution patterns, and the various singlet-triplet energy gaps were computed to predict qualitative ground state spin multiplicities. Singlet and triplet spin states were essentially degenerate in the m,m′-isomers of disjoint connectivity, while nondisjoint o,m′- and m,p′-isomers had triplet computed ground states. Nitroxide-based diradicals showed considerably smaller computational exchange coupling energies than did other diradical models studied. As a tests of these computations, stilbenes with two N-tert-butyl nitroxide groups at the o,m′-, m,m′-, and m,p′-positions were prepared, and their magnetic properties were studied by ESR and magnetic susceptibility measurements. The m,m′- and m,p′-isomers were found experimentally to have singlet and triplet ground states, respectively, in accord with the qualitative computed predictions.

Original languageEnglish
Pages (from-to)4272-4280
Number of pages9
JournalJournal of Organic Chemistry
Issue number15
Publication statusPublished - 1994


ASJC Scopus subject areas

  • Organic Chemistry

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