Influence of the microsolvation on hemibonded and protonated hydrogen sulfide: infrared spectroscopy of [(H2S)n(X)1]+ and H+(H2S)n(X)1 (n = 1 and 2, X = water, methanol, and ethanol)

Abstract

Changes of the excess charge accommodation motif in hemibonded and protonated hydrogen sulfide by microsolvation are studied by infrared spectroscopy of [(H₂S)_n(X)₁]⁺ and H⁺(H₂S)_n(X)₁ (n = 1 and 2, X = water, methanol, and ethanol) clusters. While the hemibond in the (H₂S)₂⁺ ion core is stable to the microhydration by a single water molecule, the hemibond is broken by the proton transfer with the microsolvation by a single methanol or ethanol molecule. Hetero hemibond formation between hydrogen sulfide and these solvent molecules is not observed. On the other hand, the excess proton in H⁺(H₂S)_n can be easily transferred to the solvent molecule, even though the proton affinity of the solvent molecule is lower than that of hydrogen sulfide. Implications of these results to the charge accommodation by sulfur under the biological conditions are discussed.