Reactivity properties of the HOSO and HSO2 isomers in liquid medium: a sequential Monte Carlo/quantum mechanics study

Abstract

Understanding the atmospheric sulfur cycle is fundamental in developing actions to mitigate its effects on acid rain formation. Solvation of HOSO and HSO2 species has been indicated as a possible pathway in sulfur acid formation. To observe differences in the behavior of these isomers in the water medium, electrical and reactivity properties -electronic chemical potential (µ), chemical hardness (η), and electrophilicity (ϵ)-have been obtained. Once the respective first solvation shells (15H2O for HSO2 and 23 H2O for HOSO) are considered, an increase of 25% in the dipole moment of HSO2 was observed, while the dipole moment of HOSO decreases in 11%. Both solvated isomers become softer (η decreases) compared to gas phase. Methods: HOSO and HSO2 radicals in the presence of water are investigated through a sequential Monte Carlo/Quantum Mechanics methodology. There, the intermolecular Reactivity properties of the HOSO and HSO 2 isomers in liquid medium interactions are described by the Lennard-Jones plus the Coulomb potentials. For this, the DICE program was employed. The quantum calculations were performed at CASPT2/aug − cc − pV(T+d)Z level of theory through MOLPRO computational package.

Approximating Electrostatic Potential of Molecules with Point Charges Mimicking the Electron Pairs

“…By applying expressions ( 6), (8), and (9) to the localized approximation (4) of the charge density of the molecule, we now obtain multipole moments corresponding to the electron pairs of each atom or covalent bond in the molecule. However, the direct use of expression (5) with such multipole moments for practical computations of the electrostatic potential of the molecule (for example, in the packages performing molecular dynamics simulations) would require the implementation of separate functions for calculating the dipole, quadrupole, and, if necessary, higher multipole moments. In contrast, each term of series (5) can further be modeled using a system of several point charges, provided that such a system of charges has the correct value of the corresponding multipole moment, and that it has zero values for all lower-order multipole moments, which are modeled by their own system of charges.…”

“…The accurate determination of the intermolecular interaction energy is essential for obtaining the reliable results in the physical modeling of molecular systems with such methods as molecular dynamics [1][2][3][4], Monte Carlo [5][6][7], molecular docking [8][9][10] C i t a t i o n: Nikolaienko T.Yu., Bulavin L.A. Approximating electrostatic potential of molecules with point charges mimicking the electron pairs. Ukr.…”