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Keywords:

  • H2S dimer;
  • hydrogen bonds;
  • methanol;
  • noncovalent interactions;
  • VUV-IR spectroscopy

Abstract

The nature of the S[BOND]H⋅⋅⋅S hydrogen-bonding interaction in the H2S 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[BOND]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[BOND]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[BOND]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[BOND]H⋅⋅⋅O and O[BOND]H⋅⋅⋅S interactions are possible, is S-H⋅⋅⋅O bound.