Spectroscopic Identification of the •SSNO Isomers

Elusive [S, S, N, O] isomers including the perthiyl radical •SSNO are S/N hybrid species in the complex bioinorganic chemistry of signaling molecules H₂S and •NO. By mixing thermally generated disulfur (S₂) with •NO in the gas phase, •SSNO was generated and subsequently isolated in cryogenic Ar- and N₂-matrices at 10.0 K and 15.0 K, respectively. Upon irradiation with a 266 nm laser, •SSNO isomerizes to novel sulfinyl radicals cis-NSSO• and trans-NSSO• as well as thiyl radicals cis-OSNS• and trans-OSNS•, which have been characterized by combining matrix-isolation IR (¹⁵N-labeling) and UV/Vis spectroscopy and quantum chemical calculations at the CCSD(T)-F12/cc-pVTZ-F12 level of theory. The photo-induced reversible interconversion between NSSO• and OSNS• has also been observed.