Department of Physical Chemistry II, Ruhr-University Bochum, 44780 Bochum, Germany.
J Am Chem Soc. 2012 Jan 18;134(2):1030-5. doi: 10.1021/ja207929u. Epub 2011 Dec 19.
The details of ion hydration still raise fundamental questions relevant to a large variety of problems in chemistry and biology. The concept of water "structure breaking" and "structure making" by ions in aqueous solutions has been invoked to explain the Hofmeister series introduced over 100 years ago, which still provides the basis for the interpretation of experimental observations, in particular the stabilization/destabilization of biomolecules. Recent studies, using state-of-the-art experiments and molecular dynamics simulations, either challenge or support some key points of the structure maker/breaker concept, specifically regarding long-ranged ordering/disordering effects. Here, we report a systematic terahertz absorption spectroscopy and molecular dynamics simulation study of a series of aqueous solutions of divalent salts, which adds a new piece to the puzzle. The picture that emerges from the concentration dependence and assignment of the observed absorption features is one of a limited range of ion effects that is confined to the first solvation shell.
水合离子的细节仍然引起了与化学和生物学中各种问题相关的基本问题。在水溶液中，离子“破坏”和“形成”水的结构的概念被用来解释 100 多年前引入的 HOFMEISTER 序列，该序列仍然是解释实验观察结果的基础，特别是生物分子的稳定/不稳定。最近的研究使用最先进的实验和分子动力学模拟，对结构形成/破坏概念的一些关键点提出了挑战或支持，特别是关于长程有序/无序效应。在这里，我们报告了一系列二价盐的水溶液的太赫兹吸收光谱和分子动力学模拟的系统研究，这为这个难题增加了一个新的方面。从观察到的吸收特征的浓度依赖性和归属中出现的情况是，离子的影响范围有限，仅限于第一溶剂化壳。
