Cis and trans olefin radicals: Equilibrium and photoisomerization

T. W. Ebbesen, R. Akaba, K. Tokumaru, Masakazu Washio, S. Tagawa, Y. Tabata

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Abstract

Electrochemical reduction of 1,2-bis(1-methyl-4-pyridino)ethylene dication gives the same reduction potentials (-0.53 and -0.72 V vs SCE in CH 3CN) for both cis and trans isomers. Only the absorbance spectrum of the trans radical (ε(max) 57 000 M-1 cm-1 at 517 nm) is observed. However, by using pulse radiolysis the radicals of both cis and trans isomers are observed in aqueous solution. Although their absorbance spectra are similar, the extinction coefficients are very different. The cis radical is intrinsically stable but undergoes rapid electron exchange with the trans dication isomer. Cis and trans radicals equilibrate through electron exchange, the limiting rate constants in both directions of the equilibrium being 2 × 109 M-1 s-1 (cis to trans) and 3 × 108 M-1 s-1 (trans to cis). The photoisomerization of the olefin radicals is essentially one-way: the quantum yield for the cis radical is 0.2, while that of the trans is less than 0.01.

Original languageEnglish
Pages (from-to)2147-2151
Number of pages5
JournalJournal of the American Chemical Society
Volume110
Issue number7
Publication statusPublished - 1988
Externally publishedYes

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ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Ebbesen, T. W., Akaba, R., Tokumaru, K., Washio, M., Tagawa, S., & Tabata, Y. (1988). Cis and trans olefin radicals: Equilibrium and photoisomerization. Journal of the American Chemical Society, 110(7), 2147-2151.