EPR Studies at High-Pressures. V. Spin-Exchange Reactions of Nitroxide Radicals with Cobalt and Nickel Complexes

Yoshimi Sueishi, Hajime Inoue, Tetsuhito Oka, Hiroshi Tsukube, Shunzo Yamamoto

Research output: Contribution to journalArticle

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Abstract

The rate constants k ex for the spin exchange of nitroxides with various kinds of cobalt(II) and nickel(II) complexes were determined from the EPR line-broadening of nitroxides. The rate constants estimated were in the range of 108-10 9 M -1 s -1 and this reaction was found to be diffusion-controlled. In order to distinguish cases of strong and weak spin exchange, we examined the pressure dependence of the spin exchange between nitroxide and the complexes. It was found that the ligand in the first coordination sphere of the complexes plays an important role for the efficiency of spin exchange. The presence of the coordinated halide ion provides strong exchange, regardless of any screening of the complex's internal atoms by organic molecules. From the pressure dependence of k ex, the J 2 f x values (the exchange integral J and the steric factor f s) for the spin exchange of nitroxides with cobalt and nickel complexes were estimated to be about 10 20 s -2. Based on the results, the steric hindrance for the reaction of spin exchange is discussed.

Original languageEnglish
Pages (from-to)817-823
Number of pages7
JournalBulletin of the Chemical Society of Japan
Volume71
Issue number4
Publication statusPublished - Apr 1998

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Cobalt
Nickel
Paramagnetic resonance
Rate constants
Screening
Ions
Ligands
Atoms
Molecules
nitroxyl

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

EPR Studies at High-Pressures. V. Spin-Exchange Reactions of Nitroxide Radicals with Cobalt and Nickel Complexes. / Sueishi, Yoshimi; Inoue, Hajime; Oka, Tetsuhito; Tsukube, Hiroshi; Yamamoto, Shunzo.

In: Bulletin of the Chemical Society of Japan, Vol. 71, No. 4, 04.1998, p. 817-823.

Research output: Contribution to journalArticle

Sueishi, Yoshimi ; Inoue, Hajime ; Oka, Tetsuhito ; Tsukube, Hiroshi ; Yamamoto, Shunzo. / EPR Studies at High-Pressures. V. Spin-Exchange Reactions of Nitroxide Radicals with Cobalt and Nickel Complexes. In: Bulletin of the Chemical Society of Japan. 1998 ; Vol. 71, No. 4. pp. 817-823.
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