Ab Initio Investigation of the Structure of Hydrogen Halide - Amine Complexes in the Gas Phase and in a Polarizable Medium
International Journal of Quantum Chemistry
The geometries of all 12 complexes in which HF, HCl, or HBr is paired with NH3, NMeH2, NMe2H, or NMe3 are optimized with the MINI-1 basis set. As the basicity of the amine is increased via progressive methylation, or as the proton affinity of the halide is diminished, the proton equilibrium position shifts toward the nitrogen, but in no case is this shift far enough to classify the complex as an ion pair. When the effects of a polarizable medium are included via the SCRF formalism, the shift of the proton toward the nitrogen is enhanced by increases in the solute-solvent interaction such that relatively modest coupling leads to complexes of ion-pair type. In all cases, complexes containing HBr are the most sensitive to either the basicity of the amine or the influence of the medium whereas the HF analogs are affected very little.
Ab Initio Investigation of the Structure of Hydrogen Halide - Amine Complexes in the Gas Phase and in a Polarizable Medium I. J. Kurnig and S. Scheiner Int. J. Quantum Chem., 1987, 32, Issue S14, 47-56.