title: Structural, energetic, spectroscopic and QTAIM analyses of cation-π interactions involving mono- and bi-cyclic ring fused benzene systems.
abstract: The effect of increasing the number of monocyclic six-membered rings or bicyclic rings of bicyclo[2.1.1]hexenyl fused to benzene on cation-π interactions involving alkali metal ions (Li(+), Na(+), and K(+)) has been investigated. The binding energy data at the B3LYP/6-311+G(2d,2p) level clearly indicate that the binding affinity of the metal ion with benzene is enhanced by increasing the number of rings fused irrespective of a monocyclic or a bicyclic ring. Calculated binding energies are in good agreement with the available experimental results. The binding strength of cations with ligands decreases in the order Li(+) > Na(+) > K(+). Our study establishes that trisannelation of bicyclo[2.1.1]hexene to benzene facilitates a very strong interaction between benzene and cations. Infrared (IR) frequencies and nuclear magnetic resonance (NMR) chemical shifts are shown to be valuable in characterizing cation-π interactions. The C-C bonds of the central six-membered rings are weakened due to metal ion binding. Based on the Quantum Theory of Atoms in Molecules (QTAIM), we have observed the presence of stabilizing H∙∙∙H interactions in two of the considered systems as opposed to the frequent description of these interactions as non-bonded repulsive interactions. Alkali metal ion binding with those two ligands slightly reduces the strength of such H∙∙∙H interactions.
authors.affiliation: Interdisciplinary Center for Nanotoxicity, Department of Chemistry and Biochemistry, Jackson State University, 1400 J.R. Lynch Street, P.O. Box 17910, Jackson, MS 39217, USA. dina@icnanotox.org jerzy@icnanotox.org.
authors.forename: Ayorinde
authors.initials: A
authors.lastname: Hassan
authors.forename: Tandabany C
authors.initials: TC
authors.lastname: Dinadayalane
authors.forename: Sławomir J
authors.initials: SJ
authors.lastname: Grabowski
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski