Structure and photochemistry of nitrous acid–methanethiol complexes in solid argon

The products formed in the CH3SH/HONO/Ar matrices after their deposition and after irradiation with λ > 345 nm have been studied by FTIR spectroscopy and DFT/B3LYP/aug-cc-pVTZ method. The spectra recorded directly after matrix deposition indicated formation of the CH3SH⋯HONO complexes stabilized by the OH⋯S bond. The irradiation of the matrices produced CH3SNO⋯H2O complexes. In more concentrated matrices the CH3SSCH3, (NO)2, and N2O photoproducts were also detected. The presence of both dopants: CH3SH and HONO was essential in the formation of (NO)2 and N2O in the studied systems. The reactions leading to photoproducts are proposed. The structures of the complexes present in the studied matrices, CH3SH⋯HONO and CH3SNO⋯H2O, are discussed on the basis of comparison of their theoretical spectra with the experimental ones.

► CH3SHHONO complexes trapped in solid argon are stabilized by the S⋯HO bonds.
► Irradiation (λ > 345 nm) of CH3SHHONO complexes converts them to CH3SNOH2O ones.
► CH3S mediates formation of N2O and (NO)2 photoproducts in concentrated CH3S/HONO/Ar matrices.
► All identified photoproducts originate from the sulfur–hydrogen abstraction by OH radical.