Department of Chemistry, Francis Marion University, Florence, South Carolina, USA.
J Comput Chem. 2023 May 15;44(13):1278-1290. doi: 10.1002/jcc.27082. Epub 2023 Feb 2.
The quantum theory of atoms-in-molecules (QTAIM) method is used to examine the OO bond in peroxides (RO-OR) and nitroxide dimers (R NO-ONR ), including Fremy's salt. The electron density (ρ), electron kinetic energy density [K(ρ)], and Laplacian of the electron density (∇ ρ) at bond critical points characterize the nature of the OO bond. The data distinguish OO bonding of two kinds. Large values of ρ and positive ∇ ρ and K(ρ) suggest that simple peroxides have charge-shift bonds. Nitroxide dimers, with smaller ρ, positive ∇ ρ, and near-zero K(ρ), show a lack of shared electron density, suggesting there is no conventional OO bonding in these molecules. QTAIM analysis at the B3LYP/6-311+G(d,p) level of theory gives results in agreement with valence-bond theory and X-ray diffraction characterizations of peroxide OO bonds as charge-shift bonds. In contrast, CCSD/cc-pVDZ calculations fail to agree with previous results because of an insufficient, single-determinant treatment of the charge-shift bond.
原子分子量子理论 (QTAIM) 方法用于研究过氧化物 (RO-OR) 和氮氧自由基二聚体 (R NO-ONR ) 中的 OO 键，包括 Fremy 盐。键临界点处的电子密度 (ρ)、电子动能密度 [K(ρ)] 和电子密度的拉普拉斯 (∇ ρ) 用于描述 OO 键的性质。这些数据区分了两种 OO 键合。较大的 ρ 值、正的 ∇ ρ 和接近零的 K(ρ) 表明简单的过氧化物具有电荷转移键。氮氧自由基二聚体的 ρ 值较小、∇ ρ 为正且 K(ρ) 接近零，表明这些分子中没有共享的电子密度，这表明它们之间没有传统的 OO 键。B3LYP/6-311+G(d,p) 理论水平的 QTAIM 分析结果与价键理论和过氧化物 OO 键的 X 射线衍射特征一致，表明这些键是电荷转移键。相比之下，CCSD/cc-pVDZ 计算由于对电荷转移键的处理不足（仅为单行列式）而无法与之前的结果一致。
