Dimerization Reaction of Regioisomeric Bis(phenylethynyl)benzene Radical Anions during Pulse Radiolysis

Authors

  • Prof. Dr. Mamoru Fujitsuka,

    1. The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047 (Japan)
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  • Dr. Shingo Samori,

    1. The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047 (Japan)
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  • Sachiko Tojo,

    1. The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047 (Japan)
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  • Prof. Dr. Michael M. Haley,

    1. Department of Chemistry and the Materials Science Institute, University of Oregon, Eugene, Oregon 97403-1253 (USA)
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  • Prof. Dr. Tetsuro Majima

    Corresponding author
    1. The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047 (Japan)
    • The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047 (Japan)
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Abstract

Dimerization of a series of regioisomeric 1,4-, 1,3-, and 1,2-bis(phenylethynyl)benzene radical anions (bPEBs.−) substituted by various electron-donor and/or electron-acceptor groups was studied during the pulse radiolysis in N,N-dimethylformamide (DMF). The transient absorption of bPEB.− decayed with the formation of new bands attributed to the dimer radical anion of bPEB.− and bPEB (bPEB2.−). From the dependence of decay and formation rates on the concentration of bPEB, the bimolecular rate constants of kb=(1.2±0.1)×107 to (3.2±0.2)×108 M−1 s−1 were estimated. It is suggested that bPEB.− dimerizes with bPEB through the formation of a C[BOND]C bond between two sp carbon atoms, to give σ-type dimer radical anion (σ-(bPEB)2.−) with a diene-type structure. The kb values of bPEB.− with bPEB changed with the substitution pattern of the phenylacetylene group on the central benzene ring and the various kinds of donor and/or acceptor group.

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