Infrared Spectra and Quantum Chemical Calculations of Group 2 MO2, O2MO2, and Related Molecules

Laser-ablated group 2 metal atoms have been reacted with O 2 in condensing N 2 to complement earlier Ar studies owing to different relaxation dynamics of N 2 and Ar with respect to excited metal atoms and ionic product molecules. In the case of Ca + O 2, the reaction in condensing Ar gives primarily the 3 B 2 open bent OCaO dioxide product, but the reaction in condensing N 2 favors the 1 A 1 cyclic CaO 2 peroxide species. Three fundamentals are observed with 18 O and 44 Ca substitution for CaO 2, and isotopic frequencies are in excellent agreement with the predictions of quantum chemical calculations. Although DFT/B3LYP frequencies are slightly higher than MP2 and CASSCF values, a similar pattern is calculated. Ionic molecules interact more strongly with a nitrogen matrix than with argon, and calculations of N 2 MO x and ArMO x molecules can be used to explain matrix shifts. Several N 2 MO 2 species are formed spontaneously from MO 2 molecules in solid nitrogen, and a match is found for observed matrix and DFT calculated isotopic frequencies. By comparison, the new molecule ArBeO 2 is identified in earlier argon matrix experiments. The new metal disuperoxide molecules, O 2 MO 2, are also identified here. Calcium disuperoxide, O 2 CaO 2, is characterized as a D 2 d species with +1.12 charge on Ca and −0.28 on each O, in contrast to calcium peroxide, CaO 2, a C 2 v molecule with +1.05 charge on Ca and −0.525 on each oxygen atom.