Infrared spectra of the C2O4+ cation and C2O4− anion isolated in solid neon

Laser ablation of transition metal targets with concurrent 4 K codeposition of CO2/Ne mixtures produces metal independent infrared absorptions at 1658.2 and 1421.6 cm−1 due to CO2− and CO2+. Additional metal independent absorptions at 2130.8 and 1274.4 cm−1, and at 1852.4, 1189.2, and 679.2 cm−1 increase on annealing to 8 K. Isotopic substitution shows that both band sets involve two equivalent CO2 subunits. Based on density functional theory calculations of structures and vibrational frequencies, the 2130.8 and 1274.4 cm−1 bands are assigned to the C2O4+ cation with C2h symmetry, and the 1852.4, 1189.2, and 679.2 cm−1 bands are assigned to the C2O4− anion with D2d symmetry. Evidence is also obtained for (CO2−)(CO2)x(x=1,2) anion complexes.