Structure, Reaction Enthalpies, Entropies, and Free Energies of Cation−Molecule Complexes. A Theoretical Study by Means of the ab Initio Complete Basis Set CBS-Q Method

Abstract

Ab initio molecular orbital calculations at the CBS-Q level of theory have been performed for 72 complexes in order to determine the effects of molecular structure on gas-phase basicity toward H+, Li+, and Mg2+. It is shown that basicities toward metal cations Li+ and Mg2+ differ considerably from the corresponding gas-phase basicities toward H+. Calculated interaction energies vary as H+ ≫ Mg2+ > Li+. The relative basicities of the bases studied depend characteristically on type of cation and coordination site.