Effect of solvation on the shapes, sizes, and anisotropies of polyatomic anions via molecular electrostatic potential topography: An ab initio self-consistent reaction field approach

The effect of solvation, as studied by the self-consistent reaction field procedure, on the shapes, sizes, and anisotropies of eight small prototypical anions (OH−, NH−2, CH−3, CN−, SH−, N−3, NO−2, and NO−3) has been studied at the ab initio 6–31++G(d) level. Both the general molecular electrostatic potential distribution and the molecular electrostatic potential topography have been used for examining the effect of solvation. The results demonstrate both the complexity and specificity of the hydration effect on the solute charge distribution. It is observed that in general anions tend to shrink upon solvation. The molecular electrostatic potential, in general, becomes more negative and the electron density is increased upon solvation. The effect of the solvation on the chemical reactivity and anisotropy of the anions in aqueous environment is discussed.