Photochemical Hydroxyl Group Abstraction from N-Hydroxypyridine-2(1H)-thione Isolated in a Solid Hydrogen Matrix: Photogeneration of 2-Mercaptopyridine

Monomers of <i>N</i>-hydroxypyridine-2(1<i>H</i>)-thione were isolated in low-temperature matrices of solid normal hydrogen (n-H₂). The matrix-isolated compound was irradiated with UV-B (λ = 305 nm) or UV-A (λ > 360 nm) light. Upon such irradiation, the initial form of <i>N</i>-hydroxypyridine-2(1<i>H</i>)-thione was completely consumed and converted into photoproducts. 2-Mercaptopyridine and water were identified as the main products of these photochemical transformations. Identification of photoproduced 2-mercaptopyridine is unquestionable. It is based on the identity of two sets of IR bands: (i) the bands observed in the IR spectrum recorded (in a separate experiment) for monomers of 2-mercaptopyridine trapped in an n-H₂ matrix and (ii) a set of IR bands observed in the spectrum recorded after UV irradiation of <i>N</i>-hydroxypyridine-2(1<i>H</i>)-thione. It should be emphasized that the UV-induced processes, occurring for <i>N</i>-hydroxypyridine-2(1<i>H</i>)-thione isolated in an n-H₂ matrix, lead to products that are significantly different from those generated from the compound trapped in solid Ar or in solid N₂.