INFRARED SPECTRA OF $MgF_{2}$ COMPLEXED WITH $O_{2}$, $N_{2}$ CO, $H_{2}S$ AND $SO_{2}$ IN AN ARGON MATRIX

Author Institution: Department of Chemistry, Rice UniversityThe asymmetric stretching frequency of $MgF_{2}$ was monitored as a function of the number of complexing molecules. The molecular complexes $MgF_{2}$ (M) x where X varies from one to four for $O_{2}$, $N_{2}$ and CO, one to three for $H_{2} s$ and one for $SO_{2}$ have been observed. It was generally found that the addition of a complexing molecule caused a decrease in the $MgF_{2}$ asymmetric frequency. The decrease was observed to be approximately the same for the addition of each successive molecule. For the $N_{2}$ complex four dinitrogen molecules cause the frequency to decrease to a value close to that of a pure $N_{2}$ matrix. Thus, there are only four important interaction sites around the $MgF_{2}$ molecule. The binding energy per molecule was estimated by taking the percent decrease in the force constant of $MgF_{2}$ as a measure of the weakening of the $MgF_{2}$ bond and assuming the loss in energy to be the minimum total binding energy for the complexing species. The bond strengths per molecule in kcal are as follows relative to $Ar: Ne(+ 3.7), Ar(0), 0_{2}(- 2,9) N_{2} (- 8.3), CO(- 12.7), H_{2}S(- 22.7)$ and $SO_{2}(- 41.6)$. A new band near $547 cm^{-1}$ appeared in all experiments where a complex, was formed and is thought to be the symmetric stretching mode of $MgF_{2}$ in the complex