Pseudo-conformer models for linear molecules: Joint treatment of spectroscopic, electron diffraction and ab initio data for the C 3 O 2 molecule

Modeling the Chemistry of Gaseous Cations Derived from Tricarbon Dioxide

Cations C_pO_q⁺ (p ≤ 7 with q = 1,2) and C_pO₃⁺ (p = 4-7) and corresponding neutrals are modeled by B3LYP/jun-cc-pVTZ to rationalize previous mass spectrometric observations of ion reactions with neutral C₃O₂. Modeling yields optimized potential energies, geometries, Mulliken spin populations, electric dipole moments, electron configurations, and thermochemical parameters. Lewis diagrams are derived. Mono- and dioxide cations typically have unbranched carbon chains, but trioxides are branched. The ions are most stable as spin doublets, but low-lying quartets are found for monoxides with even p. For trioxide ions, the quartets for p = 5,7 are lower-lying than for p = 4,6. For neutral mono- and dioxides resulting from possible electron transfer to the ions, triplets are more stable than singlets for even p. Neutral trioxides are most stable as triplets except C₅O₃ with a singlet slightly more stable. Singlet C₄O₃ and C₆O₃ are unstable with respect to CO loss. Charge transfer is likely only for C_pO⁺ (p = 1-3) and C_pO₃⁺ (p = 4, 6). Monocarbon insertion by C₃O₂ is understood as two sequential CO losses without a hypothetical C₆O₄^+• intermediate and is thermochemically favorable for all ions considered.