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

Abstract

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 2d species with +1.12 charge on Ca and -0.28 on each O, in contrast to calcium peroxide, CaO 2 , a C 2V molecule with +1.05 charge on Ca and -0.525 on each oxygen atom.

Variable character of O—O and M—O bonding in side-on (η 2 ) 1:1 metal complexes of O 2

“…This molecule is computed to have a separation between the two oxygen atoms of 1.691 Å, a strikingly long distance consistent with a bond order prediction of less than one. Similarly long bond lengths have been predicted for Group 2 MO 2 compounds by using levels of theory that provide good agreement with experimental matrix IR spectra (38,39). Thus, it would appear that just as the transition-metal systems discussed above sample a continuum of OOO bond orders intermediate between peroxide and superoxide, other molecules can continue to extend the continuum into the region of bond orders below one.…”

The predicted infrared spectrum of the hyperberyllium molecule BeOBe in its and electronic states

“…Earlier experimental and theoretical works on BeOBe [1][2][3][4] have established it as a strongly bound linear molecule with an e X 1 R þ g ground electronic state and a very low lyingã 3 R þ u excited electronic state. We have continued these studies by making an ab initio simulation of the infrared spectrum of the e X andã states.…”

“…The matrix-isolation spectrum of BeOBe was first observed by Thompson and Andrews [1,2], and electronic transitions were investigated by Merritt et al [3] using laser-induced fluorescence and resonance enhanced multi-photon ionization techniques. Experimental and ab initio studies [1,3,4] leave no doubt that the ground electronic state is a linear 1 R þ g state, and that there is a low-lying linear 3 R þ u first excited electronic state.…”

The vibrational frequencies of CaO 2 , ScO 2 , and TiO 2 : a comparison of theoretical methods

“…A diuse d function [20] is also added. The Ca basis set is the (12s 8p 5d)/[8s 6p 3d] modi®ed [21] basis set of Roos et al [22] used in our previous study [23] of CaO 2 .…”

“…We consider the same three states as in previous work [23], where a subset of these methods was applied using a slightly dierent basis set. The three states are:…”