Behavior of Ionic Liquids Around Charged Metal Complexes: Investigation of Homogeneous Electron Transfer Reactions Between Metal Complexes in Ionic Liquids

Takuya Mabe, Fumiaki Doseki, Takeyoshi Yagyu, Koji Ishihara, Masahiko Inamo, Hideo D. Takagi

    Research output: Contribution to journalArticle

    Abstract

    The second-order electron transfer reaction between the photo-excited triplet state of [Zn(TPP)]* (TPP = 5,10,15,20-tetraphenylporphyrin) and [Co(sep)]3+ (sep = sepulchrate = 1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane) was investigated in three ionic liquids (ILs, 1-R-3-methylimidazolium bis(trifluoromethylsulfonyl)imide with R = butyl, pentyl, and hexyl) and in acetonitrile. Results of electrochemical and kinetic measurements indicated that ILs dissociate in the vicinity of charged metal complexes and at electrodes, although the dissociated anionic and cationic components of the ILs seem to exist as pairs around the metal complexes. Second-order rate constants for the electron transfer reaction are 1.88 × 109, 3.65 × 107, 2.63 × 107, and 2.01 × 107 kg·mol−1·s−1 in acetonitrile and in the butyl, pentyl and hexyl ILs, respectively, at 298 K, after correction of the contribution of diffusion. The average slope of the plot of the logarithmic second-order rate constants observed in acetonitrile and ILs against the logarithmic viscosity of each solvent was − 0.84. However, the slope of the same plot was much steeper (− 4.1) when data for only the three ILs were used. Detailed analyses of the experimental results on the basis of the Latner–Levin cross relation and the Marcus theory lead to the conclusion that the solvent properties such as the dielectric constant and refractive index around the polarized/charged transition states are different from those for the bulk ILs: observed self-exchange rate constants did not exhibit the Pekar factor dependence when dielectric constants and refractive indices for bulk ILs are used.

    Original languageEnglish
    Pages (from-to)993-1020
    Number of pages28
    JournalJournal of Solution Chemistry
    Volume47
    Issue number6
    DOIs
    Publication statusPublished - 2018 Jun 1

    Fingerprint

    Ionic Liquids
    Coordination Complexes
    acetonitrile
    Rate constants
    Refractometry
    electron transfer
    Electrons
    Refractive index
    Permittivity
    liquids
    plots
    metals
    permittivity
    refractivity
    slopes
    Imides
    imides
    Interleukin-1
    Excited states
    Viscosity

    Keywords

    • Electron transfer reaction
    • Ionic liquid
    • Metal complexes

    ASJC Scopus subject areas

    • Biophysics
    • Biochemistry
    • Molecular Biology
    • Physical and Theoretical Chemistry

    Cite this

    Behavior of Ionic Liquids Around Charged Metal Complexes : Investigation of Homogeneous Electron Transfer Reactions Between Metal Complexes in Ionic Liquids. / Mabe, Takuya; Doseki, Fumiaki; Yagyu, Takeyoshi; Ishihara, Koji; Inamo, Masahiko; Takagi, Hideo D.

    In: Journal of Solution Chemistry, Vol. 47, No. 6, 01.06.2018, p. 993-1020.

    Research output: Contribution to journalArticle

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    AU - Mabe, Takuya

    AU - Doseki, Fumiaki

    AU - Yagyu, Takeyoshi

    AU - Ishihara, Koji

    AU - Inamo, Masahiko

    AU - Takagi, Hideo D.

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    AB - The second-order electron transfer reaction between the photo-excited triplet state of [Zn(TPP)]* (TPP = 5,10,15,20-tetraphenylporphyrin) and [Co(sep)]3+ (sep = sepulchrate = 1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane) was investigated in three ionic liquids (ILs, 1-R-3-methylimidazolium bis(trifluoromethylsulfonyl)imide with R = butyl, pentyl, and hexyl) and in acetonitrile. Results of electrochemical and kinetic measurements indicated that ILs dissociate in the vicinity of charged metal complexes and at electrodes, although the dissociated anionic and cationic components of the ILs seem to exist as pairs around the metal complexes. Second-order rate constants for the electron transfer reaction are 1.88 × 109, 3.65 × 107, 2.63 × 107, and 2.01 × 107 kg·mol−1·s−1 in acetonitrile and in the butyl, pentyl and hexyl ILs, respectively, at 298 K, after correction of the contribution of diffusion. The average slope of the plot of the logarithmic second-order rate constants observed in acetonitrile and ILs against the logarithmic viscosity of each solvent was − 0.84. However, the slope of the same plot was much steeper (− 4.1) when data for only the three ILs were used. Detailed analyses of the experimental results on the basis of the Latner–Levin cross relation and the Marcus theory lead to the conclusion that the solvent properties such as the dielectric constant and refractive index around the polarized/charged transition states are different from those for the bulk ILs: observed self-exchange rate constants did not exhibit the Pekar factor dependence when dielectric constants and refractive indices for bulk ILs are used.

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