title: Influence of the water molecule on cation-pi interaction: ab initio second order Møller-Plesset perturbation theory (MP2) calculations.
abstract: 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.
authors.affiliation: 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.
authors.forename: Yechun
authors.initials: Y
authors.lastname: Xu
authors.forename: Jianhua
authors.initials: J
authors.lastname: Shen
authors.forename: Weiliang
authors.initials: W
authors.lastname: Zhu
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Luo
authors.forename: Kaixian
authors.initials: K
authors.lastname: Chen
authors.forename: Hualiang
authors.initials: H
authors.lastname: Jiang
mesh_terms: D000818:Animals; D001554:Benzene / Q000737:chemistry; D002412:Cations / Q000737:chemistry*; D008744:Methylamines / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
chemical_list: D002412:Cations; D008744:Methylamines; D014867:Water; C027451:methylamine; D001554:Benzene