Pašalić Hasan, Aquino Adelia J A, Tunega Daniel, Haberhauer Georg, Gerzabek Martin H, Lischka Hans
Institute for Theoretical Chemistry, University of Vienna, Währinger Strasse 17, 1090, Vienna, Austria.
School of Pharmaceutical Sciences and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin, 300072, People's Republic of China.
J Mol Model. 2017 Apr;23(4):131. doi: 10.1007/s00894-017-3302-3. Epub 2017 Mar 23.
Cation-π interactions were systematically investigated for the adsorption of H and alkali metal cations M to pyrene by means of Møller-Plesset perturbation theory (MP2) and density functional theory (DFT). The main aims were to determine the preferred adsorption sites and how the microhydration shell influences the adsorption process. The preferred adsorption sites were characterized in terms of structural parameters and energetic stability. Stability analysis of the M-pyrene complexes revealed that the binding strength and the barrier to transitions between neighboring sites generally decreased with increasing cation size from Li to Cs. Such transitions were practically barrierless (<<1 kcal/mol) for the large Rb and Cs ions. Further, the influence of the first hydration shell on the adsorption behavior was investigated for Li and K as representatives of small and large (alkali metal) cations, respectively. While the isolated complexes possessed only one minimum, two minima-corresponding to an inner and an outer complex-were observed for microhydrated complexes. The small Li ion formed a stable hydration shell and preferentially interacted with water rather than pyrene. In contrast, K favored cation-π over cation-water interactions. It was found that the mechanism for complex formation depends on the balance between cation-π interactions, cation-water complexation, and the hydrogen bonding of water to the π-system.
利用莫勒-普列斯塞微扰理论（MP2）和密度泛函理论（DFT），对H和碱金属阳离子M吸附到芘上的阳离子-π相互作用进行了系统研究。主要目的是确定优先吸附位点以及微水合壳层如何影响吸附过程。通过结构参数和能量稳定性对优先吸附位点进行了表征。对M-芘配合物的稳定性分析表明，从Li到Cs，随着阳离子尺寸的增加，相邻位点之间的结合强度和转变势垒通常会降低。对于大的Rb和Cs离子，这种转变实际上是无势垒的（<<1千卡/摩尔）。此外，分别以Li和K作为小阳离子和大阳离子（碱金属）的代表，研究了第一水合壳层对吸附行为的影响。虽然孤立的配合物只有一个极小值，但对于微水合配合物，观察到了两个极小值——分别对应内配合物和外配合物。小的Li离子形成了稳定的水合壳层，优先与水而不是芘相互作用。相反，K更倾向于阳离子-π相互作用而不是阳离子-水相互作用。发现配合物形成的机制取决于阳离子-π相互作用、阳离子-水络合以及水与π体系之间氢键的平衡。
