Electrostatic Potential as a Harbinger of Cation Coordination: CF3SO3- Ion as a Model Example

Abstract

The topography of molecular electrostatic potential (MESP) has been proposed as a predictive tool for studying ion-pair formation, using the trifluromethanesulfonate (triflate) ion, CF3SO3- (Tf-), as a test example. A model based on electrostatic docking of the cation (Li+, Na+, NH4+) has been developed for studying the different possible coordinating geometries for these ion pairs. The interaction energies of different ion-pair structures estimated by the electrostatic docking model have been found to reproduce about 85% of the corresponding ab initio interaction energies. Furthermore, the geometries predicted by the present model indeed provide a good initial guess for a subsequent ab initio Hartree−Fock calculation. Ab initio local minima are usually found close to the respective geometries derived from the electrostatic docking, the bidentate structure being the most favored one. The topography-based approach thus seems to offer insights into primitive patterns of ion-pair formation. Electron correlat...