Production and infrared absorption spectrum of CISO₂ in matrices

A new species, ClSO₂, is produced and identified with infrared (IR) absorption spectra when an argon or krypton matrix containing Cl₂ and SO₂ is irradiated with laser emission at 355 nm. Lines at 1311.0, 1309.6, 1099.8, 1098.2, 497.7, and 455.8 cm^-1 (or 1309.5, 1098.5, 497.0, and 454.2 cm^-1) are assigned to ClSO₂ isolated in solid Ar (or Kr). Assignments of IR absorption lines are based on results of ³⁴S and ¹⁸O isotopic substitution (in solid Kr) and theoretical calculations. Theoretical calculations using density-functional theories (B3LYP and B3P86 with an aug-cc-pVTZ basis set) were performed to predict the geometry, energy, vibrational frequencies, and infrared intensities of possible isomers of ClSO₂: (pyramidal) ClSO₂, cis-ClOSO, (nonplanar) ClOSO, and cis-ClSOO. Results predicted for pyramidal ClSO₂ agree with observed experimental data. This is the first identification of ClSO₂, which is presumably an important intermediate during photolysis of Cl₂SO₂ and in the reaction of Cl with SO₂, especially at low temperatures. In addition to ClSO₂, irradiation of the Cl₂/SO₂/Ar matrix sample with laser light at 308 nm produces Cl₂SO₂. Possible mechanisms of formation are discussed.