Gas-Phase Infrared Spectroscopic Investigation of S–H···S Hydrogen Bonds in (H ₂ S) n ( n = 2–6) Clusters

High Resolution Image Download MS PowerPoint Slide While O–H···O hydrogen (H) bonds have been vigorously investigated, gas-phase studies of S–H···S H bonds remain very limited, especially in cases where multiple H bonds form a network. In this study, we investigate S–H···S H bonds in hydrogen sulfide clusters, (H 2 S) n ( n = 2–6), in the gas phase with size-selective infrared spectroscopy based on vacuum ultraviolet photoionization detection. For clusters with n ≥ 3, the H-bonded SH stretching frequency remains nearly constant irrespective of the cluster size, a trend that contrasts with previously reported observations from the Ar matrix isolation spectra. (H 2 S) n ( n > 3) clusters prefer to form dense three-dimensional H-bond networks to enhance the contribution of dispersion forces. These behaviors of (H 2 S) n significantly differ from those of the OH H-bond networks in (H 2 O) n . This study reveals that S–H···S H-bond networks in (H 2 S) n are characterized by weak cooperativity and a substantial contribution from dispersion forces.