Ab initio investigation of the CO 4 and CO 2N 2 molecules as possible high-energy metastable species

Abstract

A possibility of the CO 4 molecule existence is studied theoretically at the SCF, MP2, MP4, and CISD levels of theory using the 6-31G ∗ basis set. It is shown that there exist at least two local minima on the potential energy surface (PES) of the lowest singlet state of this molecule, corresponding to its D 2d and C 2v isomers. Both isomers are predicted to be vibrationally stable, but metastable (by 80 kcal mol − 1 and 48 kcal mol − 1 respectively) relative to the lowest dissociation asymptote CO 2( X 1 Δ∑ + g )+ O 2( a 1 Δ g ). The possible channels of decay and some possible ways of production of both CO 4 isomers are considered. The results obtained make it possible to hope that the CO 4 molecule may exist (at least at low temperatures) and may be of interest both as a possible source of the singlet oxygen O 2( a 1 Δ g ) and as an energy carrier. Based on the results of ab initio calculations performed, the existence of the local metastable minimum on the PES of the CO 2N 2 molecule, corresponding to its structural form O 2CN 2, is predicted. It is shown that the adiabatic decay of this structure must be accompanied by the release of about 190 kcal mol − 1 of heat.