Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland.
J Phys Chem A. 2013 Aug 22;117(33):7989-8000. doi: 10.1021/jp404245q. Epub 2013 Aug 13.
Density functional and Møller-Plesset second-order perturbation (MP2) calculations have been carried out on various model cation-π complexes formed through the interactions of Mg(2+), Ca(2+), and NH4(+) cations with benzene, p-methylphenol, and 3-methylindole. Partial hydration of the metal cations was also considered in these model studies to monitor the effect of hydration of cations in cation-π interactions. The binding energies of these complexes were computed from the fully optimized structures using coupled cluster calculations including triple excitations (CCSD(T)) and Gaussian-G4-MP2 (G4MP2) techniques. An analysis of the charge sharing between the donor (the π-systems) and the acceptors (the cations) together with the partitioning of total interaction energies revealed that the strong and weak cation-π interactions have similar electrostatic interaction properties. Further decomposition of such electrostatic terms into their multipolar components showed the importance of the charge-dipole, charge-quadrupole, and charge-octopole terms in shaping the electrostatic forces in such interactions. The computed vibrational spectra of the complexes were analyzed for the specific cation-π interaction modes and have been shown to contain the signature of higher order electrostatic interaction energy components (quadrupole and octopole) in such interactions.
已对通过 Mg(2+)、Ca(2+)和 NH4(+)阳离子与苯、对甲基苯酚和 3-甲基吲哚相互作用形成的各种模型阳离子-π 配合物进行了密度泛函和 Møller-Plesset 二阶微扰 (MP2) 计算。在这些模型研究中还考虑了金属阳离子的部分水合作用，以监测阳离子在阳离子-π 相互作用中水合对阳离子的影响。使用包括三重激发 (CCSD(T)) 和 Gaussian-G4-MP2 (G4MP2) 技术的耦合簇计算从完全优化的结构计算了这些配合物的结合能。对供体（π 体系）和受体（阳离子）之间电荷共享的分析以及总相互作用能的分配表明，强和弱的阳离子-π 相互作用具有相似的静电相互作用特性。对这些静电项进一步分解为其多极分量表明，在这些相互作用中，电荷-偶极子、电荷-四极子和电荷-八极子项在形成静电力方面的重要性。对配合物的振动光谱进行了分析，以确定特定的阳离子-π 相互作用模式，并表明在这些相互作用中存在更高阶静电相互作用能分量（四极子和八极子）的特征。
