Mixed H<sub>2</sub>S and H<sub>2</sub>O ClustersNew\nInsights into Dispersion-Dominated Hydrogen Bonding

Here, we report the results of an IR spectroscopy study\non heteroclusters\nof H<sub>2</sub>S and H<sub>2</sub>O and several of their isotopomers\nusing mass-selective IR spectroscopy in superfluid helium nanodroplets\nin the range of 2560–2800 cm<sup>–1</sup>. Based on\nDFT calculations on the B3LYP-D3/6-311++G(d,p) level of theory, we\nwere able to assign the experimentally observed O–D stretching\nbands to heterodimer and heterotrimer clusters. Since no bands of\nthe S–H-bound conformer HSH···OH<sub>2</sub> could be observed, we were able to determine the O–H-bound\nconformer HOH···SH<sub>2</sub> to be the global minimum\nstructure. A trapping of the local minima in helium nanodroplets was\nnot observed. This is in line with the weaker hydrogen bond expected\nfor H<sub>2</sub>S complexes. In these clusters, the interaction energy\nis expected to be more dominated by dispersion and less dictated by\nhighly directional electrostatic forces.