Computational study of the interaction between NO, NO⁺, and NO^- with H₂O

In this computational study the interaction of NO^., NO⁺, and NO^- with H₂O: [NO--H₂O]^., 1 ^., [NO--H₂O]⁺, 1 ⁺ , and [NO--H₂O]^-, 1 ^- was analysed. The optimized geometries indicate that the relative position of NO and H₂O depends on the total charge: (ON^.--H-OH), (NO^---H-OH), and (ON⁺--OH₂). Moreover, atomic spin density along with frontier molecular orbitals help to identify the preferred reduction or oxidation sites on the nitric oxide. Thus, quantum theory of atoms in molecules (QTAIM), electron localization function (ELF), and natural bond-bond polarizability (NBBP) methods aid to quantify the electron delocalization level between NO and H₂O, 1 ⁺ > 1 ^. > 1 ^- , and show the predominantly ionic, and covalent character to inter-molecular, and intra-molecular chemical bonds, respectively. Furthermore, the natural bond orbital (NBO) and localized molecular orbital energy decomposition analysis (LMO-EDA) methods enable energy analyses of the interaction between NO and H₂O in the complexes 1 ^., 1 ⁺ , and 1 ^- . Where, the first method showed that the interaction between the natural bond orbitals in 1 ^- is more favorable, than in 1 ⁺ , and less in 1 ^., however, the second method designates that the total interaction energy is lower for 1 ⁺ in relation to 1 ^- and 1 ^., due mainly to the electrostatic component. As a final point, analysis of the electrostatic potential surfaces provides a clear and direct explanation for the relative position of the monomers. It also shows that the predominant Coulombic attraction between H₂O and the charged NO⁺, and NO^- compounds will be stronger in relation to the neutral NO^.. Graphical abstract ᅟ.