离子对水溶液微观结构和动力学的影响  

Ion effect on the structures and dynamics of aqueous solutions

作　　者：张强[1] 李燕均[1] 庄巍[2] 

机构地区：[1]渤海大学化学化工学院,锦州121000 [2]分子反应动力学国家重点实验室,中国科学院大连化学物理研究所,大连116023

出　　处：《中国科学：化学》2016年第1期51-58,共8页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(21373201,21033008);教育部留学回国人员科研启动基金资助

摘　　要：离子对水溶液结构和动力学性质的影响具有特异性,本文对此进行了一系列的分子模拟研究,发现一价单原子离子的溶解结构与阴离子-阳离子、离子-水和水-水之间的竞争作用有关,离子间成对趋势符合Collins规则,以水分子为桥的离子对结构是离子在水中溶解的重要方式,并具有不对称性.在Na SCN和KSCN极稀水溶液中,盐对水分子活动性影响体现为阴、阳离子效应的叠加,符合Hofmeister离子序和Jones-Dole黏度B系数的定量趋势,随着浓度增大,离子协同性和离子团簇的影响逐渐增强,浓溶液中普遍具有拖慢效应.水溶液中水分子转动与氢键交换相关,存在大角度跳跃转动和氢键对协同扩散转动两种方式,阴离子效应主要体现在对跳跃转动的影响,由阴离子与水分子间氢键强度决定,阳离子主要通过间接方式同时影响两种方式,影响程度与电荷密度有关.The ion effect on the structures and dynamics in aqueous solutions is specific. We carried out a series of molecular simulations to explore it at molecule level. Our simulation results suggest that the pairing preferences of a series of mono-atomic 1：1 ions follow Collins＇ rule. The water-bridging ion pair is an important microscopic structure in aqueous solutions. In dilute KSCN and NaSCN aqueous solutions, the effect of anion and cation on the water mobility is additive and consistent with the Hofmeister series qualitatively and the prediction of Jones-Dole viscosity B-coefficient quantitatively. As the concentration increases, effect enhances. In concentrated aqueous solution, there is the cooperative effect of anion and cation and ion-cluster a retarding effect on the water dynamics exerted by any salt. The rotation of water is closely related to the hydrogen bond switching process. The rotation of water can be decomposed into a large-magnitude angular jump rotation and the frame diffusive rotation of the hydrogen bond pair. For anion, the strength of hydrogen bond directly formed by anion and water determines on the jump rotational mobility. The jump and frame diffusive rotations of water are both affected by the surrounding cations indirectly. The strength of cation effect is closely related to the charge density of cation.

关 键 词：盐效应 离子对 氢键交换 跳跃转动 超快红外光谱 

分 类 号：O645.1[理学—物理化学]