Matrix-isolation FTIR study of carbon dioxide: Reinvestigation of the CO2 dimer and CO2⋯N2 complex

Carbon dioxide isolated in argon and nitrogen matrices was reinvestigated through FTIR spectroscopy. The study of the variation of the IR absorptions with the concentration of CO2 in the matrix, and also with the addition of different amounts of N2 (present as an impurity in the Ar gas) was performed. Some of the bands were reassigned to the CO2 dimer and CO2⋯N2 complex and some others, like the symmetric stretching mode for the CO2 dimer and the (ν1 + ν3) and (2ν2 + ν3) combination bands for the CO2 dimer and that of the CO2⋯N2 complex, were reported for the first time. The bonding properties of the (CO2)2 and CO2⋯N2 complexes have been interpreted by a Natural Bond Orbital (NBO) analysis in terms of “donor–acceptor” interactions.