Can low-barrier hydrogen bond exist in systems with second row elements? An ab initio path integral molecular dynamics study for deprotonated hydrogen sulfide dimer

Abstract

Nuclear quantum effect and thermal effect on deprotonated hydrogen sulfide dimer anion ${\text{H}}_{3} {\text{S}}_{2}^{-}$, composed of a second row element, are widely explored by ab initio on-the-fly path integral molecular dynamics simulation. At low temperature, the hydrogen-bonded proton tends to be diffusively located at the central position between two sulfur atoms, which is the typical characteristic feature of so-called low-barrier hydrogen bond (LBHB). This is the first case of the LBHB systems composed of the second row elements, although the hydrogen-bonded distance in ${\text{H}}_{3} {\text{S}}_{2}^{-}$ (over 3.4 Å) is much longer than the previously reported LBHB composed of first row elements (<2.5 Å). At high temperature, the distance between two sulfur atoms is longer than that at low temperature, and the hydrogen-bonded proton localizes to each sulfur atom. Similar tendency is obtained in the deuterated ${\text{D}}_{3} {\text{S}}_{2}^{-}$ species at all temperature. Analyzing the relationship between the position of the hydrogen-bonded proton and the quantum fluctuation effect of the proton, we elucidate that the LBHB is induced by the quantum tunneling at low temperature, while such trend becomes weak and the character of LBHB vanishes at room temperature for ${\text{H}}_{3} {\text{S}}_{2}^{-}$.