Xu Yechun, Shen Jianhua, Zhu Weiliang, Luo Xiaomin, Chen Kaixian, Jiang Hualiang
Center for Drug Discovery and Design, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, People's Republic of China.
J Phys Chem B. 2005 Mar 31;109(12):5945-9. doi: 10.1021/jp044568w.
The influence of introducing water molecules into a cation-pi complex on the interaction between the cation and the pi system was investigated using the MP2/6-311++G method to explore how a cation-pi complex changes in terms of both its geometry and its binding strength during the hydration. The calculation on the methylammonium-benzene complex showed that the cation-pi interaction is weakened by introducing H(2)O molecules into the system. For example, the optimized interaction distance between the cation and the benzene becomes longer and longer, the transferred charge between them becomes less and less, and the cation-pi binding strength becomes weaker and weaker as the water molecule is introduced one by one. Furthermore, the introduction of the third water molecule leads to a dramatic change in both the complex geometry and the binding energy, resulting in the destruction of the cation-pi interaction. The decomposition on the binding energy shows that the influence is mostly brought out through the electrostatic and induction interactions. This study also demonstrated that the basis set superposition error, thermal energy, and zero-point vibrational energy are significant and needed to be corrected for accurately predicting the binding strength in a hydrated cation-pi complex at the MP2/6-311++G level. Therefore, the results are helpful to better understand the role of water molecules in some biological processes involving cation-pi interactions.
使用MP2/6 - 311++G方法研究了将水分子引入阳离子 - π复合物中对阳离子与π体系之间相互作用的影响，以探索阳离子 - π复合物在水合过程中其几何结构和结合强度如何变化。对甲基铵 - 苯复合物的计算表明，通过向体系中引入H₂O分子，阳离子 - π相互作用会减弱。例如，随着水分子逐个引入，阳离子与苯之间优化后的相互作用距离变得越来越长，它们之间转移的电荷越来越少，阳离子 - π结合强度越来越弱。此外，第三个水分子的引入导致复合物几何结构和结合能都发生显著变化，从而导致阳离子 - π相互作用的破坏。结合能分解表明，这种影响主要通过静电和诱导相互作用产生。该研究还表明，基组叠加误差、热能和零点振动能很显著，在MP2/6 - 311++G水平上准确预测水合阳离子 - π复合物的结合强度时需要对其进行校正。因此，这些结果有助于更好地理解水分子在一些涉及阳离子 - π相互作用的生物过程中的作用。
