Samples formed by codepositing S2 from a superheater source with Ar/O2 on a 10 K substrate exhibit very strong 1403.0-cm-1 and weaker 725.5-cm-1 infrared absorptions. Photolysis decreases these bands slightly and produces SO2 and S2O. The infrared bands show 18O2 and 34S2 shifts appropriate for O-O and S-S fundamental vibrations, and triplet absorptions in mixed isotopic experiments suggesting two equivalent O and two equivalent S atoms in the product complex. Similar results were obtained for Se2 and O2; new absorptions appeared at 1404.5 and 391 cm-1. Ab initio calculations at the SCF, CISD, and CCSD levels of theory failed to find a complex with the observed spectroscopic properties. However, calculations with the BP density functional characterized a singlet (S2)(O2) parallelogram structure bound by 15.6 kJ/mol relative to triplet S2 and O2 with the O-O stretching frequency red-shifted 187 cm-1 and the S-S fundamental blue-shifted 20 cm-1. This weakly bound (S2)(O2) complex is chemically intermediate between the unstable O4 and stable S4 molecules. The argon matrix has made possible the formation of the weak (S2)(O2) complex and DFT with the BP functional has characterized this weak charge-transfer interaction.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the American Chemical Society|
|State||Published - Jun 12 1996|