Structural and dynamical properties of nitrite ion in aqueous solution

Abstract

The knowledge of hydration properties for the nitrite ion is a key to understand its reaction mechanism controlled by the solvent effects. Here, the ab initio quan- tum mechanical charge field molecular dynamics method was performed to acquire the structural and dynamical properties of hydration shell on an aqueous solution of nitrite ion, elucidated by the data analysis with molecular approach and an ex- tended quantitative analysis of all superimposed trajectories with three-dimensional alignment (density map). The pattern of power spectra corresponded with the ex- perimental data, indicating a decency of the Hartree-Fock method coupling with the double-ζ plus polarization and diffuse functions basis sets to study this system. The density maps revealed the structure of hydration shell that there presented a higher density in the N − O bond directions than the vertical axis to the molecular plane, whereas the atomic and molecular radial distribution functions provided the vague information. The number of actual contacts specified 4.6 water molecules interacting with the nitrite ion, and 1.5 extra waters, also located in the molecular hydration shell, forming a H-bonding network with the bulk water. The mean residence times for the water ligands designated the strength of the hydration spheres for the oxy- gen sites, whilst the results of nitrogen site exhibited an over-counting of waters from other sites and a weak structure. These results evince the influence of water molecules surrounding the nitrite ion, creating an anisotropic hydration shell that it suggests the reactive sites situated above and below its molecular plane via a lower water density.