First detection of the C 2 symmetric isomer of carbon pentaoxide (CO 5) at 10 K

Abstract

Carbon oxides of the form CO n ( n = 2–8) have long been known as important molecules in atmospheric and solid state chemical reactions. These higher order carbon oxides have been theoretically predicted to be stable, however, their detection has been difficult. Here, we report on the first spectroscopic detection of the cyclic (C 2) isomer of carbon pentaoxide ( 12C 16O 5) via its ν 1 vibrational mode centered around 1912 cm −1 under matrix isolation conditions; the identification of the 12C 18O 5, 13C 16O 5, and 13C 18O 5, isotopologues supported by ab initio calculations confirms the assignments. We also discuss possible formation routes of this molecule.