The intermolecular S-H⋯Y (Y=S,O) hydrogen bond in the H₂S dimer and the H₂S-MeOH complex

The nature of the S-H⋯S hydrogen-bonding interaction in the H ₂S dimer and its structure has been the focus of several theoretical studies. This is partly due to its structural similarity and close relationship with the well-studied water dimer and partly because it represents the simplest prototypical example of hydrogen bonding involving a sulfur atom. Although there is some IR data on the H₂S dimer and higher homomers from cold matrix experiments, there are no IR spectroscopic reports on S-H⋯S hydrogen bonding in the gas phase to-date. We present experimental evidence using VUV ionization-detected IR-predissociation spectroscopy (VUV-ID-IRPDS) for this weak hydrogen-bonding interaction in the H₂S dimer. The proton-donating S-H bond is found to be red-shifted by 31 cm^-1. We were also able to observe and assign the symmetric (ν₁) stretch of the acceptor and an unresolved feature owing to the free S-H of the donor and the antisymmetric (ν₃) SH stretch of the acceptor. In addition we show that the heteromolecular H₂S-MeOH complex, for which both S-H⋯O and O-H⋯S interactions are possible, is S-H⋯O bound. S-H⋯O over O-H⋯S: The SH⋯Y (Y=S,O) hydrogen bond in the H₂S dimer and the H₂S-methanol binary complex are identified by using VUV ionization-detected IR predissociation spectroscopy (see picture). The SH⋯O interaction is preferred to the OH⋯S interaction in the latter complex.