The simplest sulfur-nitrogen hydrogen bond: matrix isolation spectroscopy of H2S·NH3

Abstract Hydrogen bonding in S–H…N systems has received little attention compared to other ogen bond motifs. To characterise S–H…N bonding, infrared spectra of the most fundamental S–H…N system—the H2S·NH3 complex—were recorded in solid argon. These experiments were complemented by high level ab initio and density functional theory calculations. The H2S symmetric stretch was observed to shift by -155.3cm-1 when mixed with NH3, while the NH3 umbrella mode was found to shift by +31.8cm-1. These, as well deuterium and 15 N isotopologue studies indicated the formation of a complex. The structure of the H2S·NH3 complex was determined to be almost identical to that of the H2O·NH3 complex, with a nearly linear S–H…N bond. A binding energy of 8.6kJmol-1 (720cm-1) was calculated at the CCSD(T) level of theory extrapolated to the complete basis set limit. Anharmonic frequency calculations at the DSD-PBEP86-D3BJ/aug-cc-pV(D+d)Z level of theory produced frequencies with a RMSD of 13cm-1 for the complex, relative to the experimental values. Comparison with previous work showed that the S–H…N bond is weaker in H2S·NH3 than the O–H…N bond in the H2O·NH3 system.