Molecular polarization maps as a tool for studies of intermolecular interactions and chemical reactivity

Maps for the interaction energy of acetone, pyrrole, furan, and pyridine with a positive unitary charge were computed using ab initio techniques, together with their molecular electrostatic potentials at the same points. The difference between the interaction and electrostatic potential maps yielded polarization maps for the molecules. Finally, maps for the interaction with a negative charge were obtained as the difference between the polarization and electrostatic potential maps. The calculations were carried out for three planes, 2 Bohr radii, 4 Bohr radii, and 8 Bohr radii from the plane containing the heavy atoms for all the molecules. At larger distances, the interaction and electrostatic maps resemble each other qualitatively; however, at shorter distances, where the polarization effects are more significant, the differences between the maps are notable. Interaction and polarization maps can be routinely evaluated for medium-sized molecules, and are likely to become an important tool in drug design and chemical reactivity.