利用 2DIR 光谱实时探测离子对动力学。

Real-time probing of ion pairing dynamics with 2DIR spectroscopy.

机构信息

Department of Chemistry, Korea University, Seoul 136-701, Korea.

出版信息

Chemphyschem. 2010 Dec 3;11(17):3632-7. doi: 10.1002/cphc.201000595.

DOI:10.1002/cphc.201000595

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.

摘要

化学交换二维红外（2DIR）光谱被应用于研究皮秒时间尺度上发生的离子对动力学。SeCN(-)离子被用作振动探针。SeCN(-)离子溶解在 N，N-二甲基甲酰胺（DMF）中具有足够长的振动寿命，并且可以在 DMF 中与 Li(+)离子形成接触离子对。接触离子对的 CN 伸缩频率从游离 SeCN(-)显著蓝移，因此游离 SeCN(-)离子在 DMF 中可以与接触离子对在光谱上明显区分开来。因此，我们能够通过使用超快 2DIR 光谱实时直接监测 Li(+)和 SeCN(-)的离子对动力学。结果，我们确定了 LiSeCN 接触离子对的离解时间常数为 420±40 ps。