Structural and spectroscopic properties of complexes formed between HNCS and SO in low temperature matrices.

Matrix isolation FTIR spectroscopy has been combined with quantum chemical calculations in the aim to characterize complexes of isothiocyanic acid HNCS with SO. The geometries of the 1:1, 1:2 and 2:1 complexes were optimized at the MP2 and DFT (B3LYPD3) levels of theory with the 6-311++G(3df,3pd) basis set. Five different HNCS⋯SO structures of the 1:1 stoichiometry were optimized. Three of them involve a weak NH⋯O hydrogen bond whereas two other geometries are stabilized by van der Waals interactions of various types. The HNCS/SO/Ar spectra analysis evidences that at least one of the three hydrogen bonded structure is present after deposition of the matrices whereas the most stable van der Waals HNCS⋯SO structure as well as complexes of the 1:2 stoichiometry were detected upon annealing.