Capture of the Sulfur Monoxide-Hydroxyl Radical Complex.

The elusive hydrogen-bonded sulfur monoxide-hydroxyl radical complex (•OH···OS), a missing intermediate in the atmospheric chemistry of SO2, was generated in the 266 nm laser photolysis of the sulfinyl radical HOSO• in cryogenic Ar-matrixes. In addition to the IR spectroscopic characterization with deuteration, its thermal conversion to HOSO• with an activation barrier of 0.33 ± 0.11 kcal mol-1 (calcd 0.32 kcal mol-1, CCSD(T)-F12a/AVTZ) in the temperature range of 15.0-21.0 K and a H/D kinetic isotope effect of 2.4 at 16.0 K have been observed.