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Real-Time Probing of Ion Pairing Dynamics with 2DIR Spectroscopy

Authors

  • Kwang-Hee Park,

    1. Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
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  • Seung Ryul Choi,

    1. Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
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  • Dr. Jun-Ho Choi,

    1. Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
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  • Prof. Dr. Sungnam Park,

    Corresponding author
    1. Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
    2. Multidimensional Spectroscopy Laboratory, Korea Basic Science Institute, Seoul 136-713 (Korea)
    • Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
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  • Prof. Dr. Minhaeng Cho

    Corresponding author
    1. Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
    2. Multidimensional Spectroscopy Laboratory, Korea Basic Science Institute, Seoul 136-713 (Korea)
    • Department of Chemistry, Korea University, Seoul 136-701 (Korea), Fax: (+82) 2-3290-3121
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  • 2DIR: Two-Dimensional Infrared

Abstract

Chemical exchange two-dimensional infrared (2DIR) spectroscopy is applied to investigate ion pairing dynamics occurring on picosecond timescales. SeCN ion is used as a vibrational probe. The SeCN ion dissolved in N,N-dimethyl formamide (DMF) has a sufficiently long vibrational lifetime and can form a contact ion pair with Li+ ion in DMF. The CN stretch frequency of the contact ion pair is significantly blue-shifted from that of free SeCN so the free SeCN ion can be spectrally distinct from the contact ion pair in DMF. Therefore, we were able to directly monitor the ion pairing dynamics of Li+ and SeCN in real time by using ultrafast 2DIR spectroscopy. As a result, we have determined the dissociation time constant of the LiSeCN contact ion pair to be 420±40 ps.

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