Large-amplitude transfer motion of hydrated excess protons mapped by ultrafast 2D IR spectroscopy
Large-amplitude transfer motion of hydrated excess protons mapped by ultrafast 2D IR spectroscopy
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DOI：
10.1126/science.aan5144
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发表时间：
2017-08-04
期刊：
影响因子：
56.9
通讯作者：
Elsaesser, Thomas
中科院分区：
文献类型：
--
作者：
Dahms, Fabian;Fingerhut, Benjamin P.;Elsaesser, Thomas
过量质子在水体系中的溶剂化和迁移在酸碱化学和生化过程中起着重要的作用。我们利用二维红外光谱绘制了超快质子沿质子转移坐标的漂移图，包括在原水中和在乙腈中选择性地制备的Zundel阳离子(H5O2)(+)模体中。来自环境的电场和随机的氢键运动导致质子双极小势的波动。在特定水化几何结构的生命周期内，质子在低于100飞秒的时间尺度上探索多个位置。质子转移振动被其20到40飞秒的布居衰变所强烈地抑制。我们的结果表明，类Zundel几何构型在水溶液中的质子溶剂化和输运中起着中心作用。
Solvation and transport of excess protons in aqueous systems play a fundamental role in acid-base chemistry and biochemical processes. We mapped ultrafast proton excursions along the proton transfer coordinate by means of two-dimensional infrared spectroscopy, both in bulk water and in a Zundel cation (H5O2)(+) motif selectively prepared in acetonitrile. Electric fields from the environment and stochastic hydrogen bond motions induce fluctuations of the proton double-minimum potential. Within the lifetime of a particular hydration geometry, the proton explores a multitude of positions on a sub-100-femtosecond time scale. The proton transfer vibration is strongly damped by its 20- to 40-femtosecond population decay. Our results suggest a central role of Zundel-like geometries in aqueous proton solvation and transport.