Carbon Dioxide Clusters And Copper Complexes Formed In Argon Matrices

Neutral and anionic clusters containing carbon monoxide and carbon dioxide molecules were observed in FTIR matrix isolation spectroscopy experiments following co-deposition of Cu$^{-}$ and Ar$^{+}$ in argon matrices doped with moderate amounts (0.1-1\%) of CO$_{2}$ and/or CO. Following deposition at 10 K with 0.5\% CO$_{2}$, peaks for CuCO$_{2}$$^{-}$ and Cu(CO$_{2}$)$_{2}$$^{-}$ were observed, along with a small peak for CO$_{2}$$^{-}$ and several bands assigned to neutral (CO$_{2}$)$_{x}$ clusters. Upon annealing to 20 K, a new peak appears at 1857 \wn, which is assigned to the C$_{2}$O$_{4}$$^{-}$ ion, based on previous work in neon matrices.\footnote{Zhou, M.F.; Andrews, L.; J. Chem. Phys. 110, 6820 (1999).} When CO is added as a dopant (0.5 \%) to the matrix gas mix, formation of the anionic copper CO$_{2}$ complexes is suppressed, and neutral CO-CO$_{2}$ complexes are observed in the spectra, as are bands corresponding to C$_{2}$O$_{3}$$^{-}$, based on previous studies.\footnote{Zhou, M.F.; et al., J. Chem. Phys. 112, 7089 (2000).} Interestingly, the copper carbonyl bands typically observed for equivalent deposition conditions in the absence of CO$_{2}$ are strongly suppressed in these spectra. The implication is that complexation with the CO$_{2}$ molecules, which are far more abundant in the matrix, inhibits the CO molecules from "finding" the Cu$^{-}$ centers during the matrix formation process. (c.f. ISMS 2014 abstract \#P616