First-principles investigations on [formula omitted] and [formula omitted] oxocarbons

Abstract

Comprehensive first-principles calculations on the geometrical and electronic properties of C5O5-/0 and C6O6-/0 oxocarbons have been performed in this work. Both C5O5- monoanion and C5O5 neutral are found to possess perfect planar pentagonal structures at their ground states D5hC5O5-(2A2″) (1) and D5h C5O5(1A2′) (2), while C6O6- and C6O6 appear to favor the slightly distorted quasi-planar C2vC6O6- (2A1) (3) and C2v C6O6 (1A1) (4), respectively. Adaptive natural density partitioning (AdNDP) analyses clearly reveal the σ- and π-bonding patterns of the monocyclic CnOn2-/-/0 oxocarbons (n=5 and 6). The adiabatic detachment energies (ADEs) and low-lying vertical detachment energies (VDEs) of the monoanions have been calculated at the coupled cluster level with triple excitations (CCSD(T)), with ADE=3.723 and VDE=3.776eV for C5O5- and ADE=3.629eV and VDE=3.679eV for C6O6- CCSD(T)//MP2. The first excited states of the neutrals are predicted to have the approximate term values of T1=1.08eV (3A2) for C5O5 and T1=1.22eV (3B1) for C6O6. The predictions made in this work may help facilitate experimental characterizations of C5O5- and C6O6- monoanions.