Li⁺、Na⁺和K⁺与杯状分子的阳离子-π相互作用的结构与能量学：苯环加成和空腔选择性的影响

Structures and energetics of the cation-pi interactions of Li+, Na+, and K+ with cup-shaped molecules: effect of ring addition to benzene and cavity selectivity.

作者信息

Dinadayalane T C, Afanasiev Dmitriy, Leszczynski Jerzy

机构信息

Computational Center for Molecular Structure and Interactions, Department of Chemistry, Jackson State University, 1400 JR Lynch Street, P.O. Box 17910, Jackson, Mississippi 39217, USA.

出版信息

J Phys Chem A. 2008 Aug 28;112(34):7916-24. doi: 10.1021/jp802236k. Epub 2008 Aug 2.

DOI:10.1021/jp802236k

PMID:18672865

Abstract

The interactions of alkali metal cations (Li (+), Na (+), and K (+)) with the cup-shaped molecules, tris(bicyclo[2.2.1]hepteno)benzene and tris(7-azabicyclo[2.2.1]hepteno)benzene have been investigated using MP2(FULL)/6-311+G(d,p)//MP2/6-31G(d) level of theory. The geometries and interaction energies obtained for the metal ion complexation with the cup-shaped systems trindene and benzotripyrrole are compared with the results for benzene-metal ion complexes to examine the effect of ring addition to the benzene on structural and binding affinities. The cup-shaped molecules exhibit two faces or cavities (top and bottom). Except for one of the conformers of tris(7-azabicyclo[2.2.1]hepteno)benzene), the metal ions prefer to bind with the top face over bottom face of the cup-shaped molecules. The selectivity of the top face is due to strong interaction of the cation with the pi cloud not only from the central six-membered ring but also from the pi electrons of rim C=C bonds. In contrast, the metal ions under study exhibit preference to bind with the bottom face rather than top face of tris(7-azabicyclo[2.2.1]hepteno)benzene) when the lone pair of electrons of three nitrogen atoms participates in binding with metal ions. This bottom face selectivity could be ascribed to the combined effect of the cation-pi and strong cation-lone pair interactions. As evidenced from the values of pyramidalization angles, the host molecule becomes deeper bowl when the lone pair of electrons of nitrogen atoms participates in binding with cation. Molecular electrostatic potential surfaces nicely explain the cavity selectivity in the cup-shaped systems and the variation of interaction energies for different ligands. Vibrational frequency analysis is useful in characterizing different metal ion complexes and to distinguish top and bottom face complexes of metal ions with the cup-shaped molecules.

摘要

已使用MP2(FULL)/6-311+G(d,p)//MP2/6-31G(d)理论水平研究了碱金属阳离子（Li(+)、Na(+)和K(+)）与杯状分子三（双环[2.2.1]庚烯基）苯和三（7-氮杂双环[2.2.1]庚烯基）苯的相互作用。将金属离子与杯状体系三茚和苯并三吡咯络合得到的几何结构和相互作用能与苯-金属离子络合物的结果进行比较，以研究苯环加成对结构和结合亲和力的影响。杯状分子有两个面或腔（顶部和底部）。除了三（7-氮杂双环[2.2.1]庚烯基）苯的一种构象外，金属离子更倾向于与杯状分子的顶面而非底面结合。顶面的选择性是由于阳离子不仅与中心六元环的π云，而且与边缘C=C键的π电子有强烈相互作用。相反，当三个氮原子的孤对电子参与与金属离子结合时，所研究的金属离子更倾向于与三（7-氮杂双环[2.2.1]庚烯基）苯的底面而非顶面结合。这种底面选择性可归因于阳离子-π和强阳离子-孤对相互作用的综合效应。从锥化角的值可以看出，当氮原子的孤对电子参与与阳离子结合时，主体分子会变成更深的碗状。分子静电势表面很好地解释了杯状体系中的腔选择性以及不同配体相互作用能的变化。振动频率分析有助于表征不同的金属离子络合物，并区分金属离子与杯状分子的顶面和底面络合物。