Determination of structure and dynamics of the solvated bisulfide (HS-) ion by ab initio QMCF molecular dynamics

The hydration structure of the bisulfide (HS(-)) ion in dilute aqueous solution was characterized by means of an ab initio quantum mechanical charge field (QMCF) molecular dynamics simulation at the Hartree-Fock level employing Dunning double-ζ plus polarization function (DZP) basis sets. An average H-S bond distance of 1.35 Å resulted from the simulation and a hydration shell located at 2.42 Å S(HS(-))···H(w) and 3.97 Å HS(-) distances, respectively. At the sulfur site, the average coordination number is 5.9 ± 1.1, while the value for the hydrogen site is 9.2 ± 1.6. The calculated H(HS(-))-S(HS(-)) stretching frequency of 2752 cm(-1) obtained from the QMCF MD simulation is in good agreement with that reported from the Raman spectrum (2570 cm(-1)) only if a scaling factor of 0.89 is applied. The stability of the nondissociated HS(-) structure is reflected by the force constants of 436.1 and 4.5 N/m determined for the H(HS(-))-S(HS(-)) and H(HS(-))···O(w) bonds, respectively. A weak structure-making effect of the hydrated HS(-) ion results from the mean residence times of 1.5 and 2.1 ps of coordinated water molecules at the sulfur and hydrogen sites of the HS(-) ion, respectively.