ELECTROSTATIC POTENTIAL AS A HARBINGER OF CATION COORDINATION - CF3SO3(-) ION AS A MODEL EXAMPLE

The topography of molecular electrostatic potential (MESP) has been pr oposed as a predictive tool for studying ion-pair formation, using the trifluromethanesulfonate (triflate) ion, CF3SO3- (Tf), as a test exam ple. A model based on electrostatic docking of the cation (Li+, Na+, N H4+) has been developed for studying the different possible coordinati ng geometries for these ion pairs. The interaction energies of differe nt ion-pair structures estimated by the electrostatic docking model ha ve been found to reproduce about 85% of the corresponding ab initio in teraction energies. Furthermore, the geometries predicted by the prese nt model indeed provide a good initial guess for a subsequent ab initi o Hartree-Fock calculation. Ab initio local minima are usually found c lose to the respective geometries derived from the electrostatic docki ng, the bidentate structure being the most favored one. The topography -based approach thus seems to offer insights into primitive patterns o f ion-pair formation. Electron correlation and the expansion of the ba sis set do not bring about any significant change in the MESP topograp hy of the anion. The interionic bonds in the NE4+Tf-, however, are rel atively sensitive to the electron correlation.