Anchor Points for the Unified Bronsted Acidity Scale: The rCCC Model for the Calculation of Standard Gibbs Energies of Proton Solvation in Eleven Representative Liquid Media
Anchor Points for the Unified Bronsted Acidity Scale: The rCCC Model for the Calculation of Standard Gibbs Energies of Proton Solvation in Eleven Representative Liquid Media
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DOI：
10.1002/chem.201003164
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发表时间：
2011-05-01
影响因子：
4.3
通讯作者：
Krossing, Ingo
中科院分区：
文献类型：
--
作者：
Himmel, Daniel;Goll, Sascha K.;Krossing, Ingo
引入COSMO簇连续体（CCC）溶剂化模型来计算质子的标准吉布斯溶剂化能。质子的溶剂化球分为具有共价相互作用的内部质子-溶剂簇和与簇发生静电相互作用的外部溶剂化球。因此，质子的溶剂化分为两个步骤，分别计算： 1）使用高级量子化学方法（改进的G3方法）在气相中计算质子与一个或多个溶剂分子的相互作用。 2)利用类导体屏蔽模型(COSMO)计算质子-溶剂团簇的吉布斯溶剂化能。对于每种溶剂，计算了至少两个（最多 11 个）质子-溶剂簇中质子的溶剂化。使用玻尔兹曼统计对所得质子吉布斯溶剂化能进行加权。以水、MeCN和DMSO的实验数据为参考，对模型计算吉布斯溶剂化能进行了评估。允许质子-溶剂簇的结构弛豫和使用结构弛豫的吉布斯溶剂化能改善了与实验数据的一致性，特别是对于较大的簇。这种变化被表示为宽松的 COSMO 簇连续体 (rCCC) 模型，我们估计该模型的 1 sigma 误差条为 10 kJmol(-1)。计算了以下代表性溶剂中质子的吉布斯溶剂化能：水、乙腈、二氧化硫、二甲亚砜、苯、乙醚、二氯甲烷、1,2-二氯乙烷、硫酸、氟磺酸和氟化氢。获得的值是质子的绝对化学标准电位（该溶剂中的pH=0）。它们用于将各个溶剂的特定酸度 (pH) 标度固定到我们最近推出的绝对酸度标度。
The COSMO cluster-continuum (CCC) solvation model is introduced for the calculation of standard Gibbs solvation energies of protons. The solvation sphere of the proton is divided into an inner proton-solvent cluster with covalent interactions and an outer solvation sphere that interacts electrostatically with the cluster. Thus, the solvation of the proton is divided into two steps that are calculated separately: 1) The interaction of the proton with one or more solvent molecules is calculated in the gas phase with high-level quantum-chemical methods (modified G3 method). 2) The Gibbs solvation energy of the proton-solvent cluster is calculated by using the conductor-like screening model (COSMO). For every solvent, the solvation of the proton in at least two (and up to 11) proton-solvent clusters was calculated. The resulting Gibbs solvation energies of the proton were weighted by using Boltzmann statistics. The model was evaluated for the calculation of Gibbs solvation energies by using experimental data of water, MeCN, and DMSO as a reference. Allowing structural relaxation of the proton-solvent clusters and the use of structurally relaxed Gibbs solvation energies improved the accordance with experimental data especially for larger clusters. This variation is denoted as the relaxed COSMO cluster-continuum (rCCC) model, for which we estimate a 1 sigma error bar of 10 kJmol(-1). Gibbs solvation energies of protons in the following representative solvents were calculated: Water, acetonitrile, sulfur dioxide, dimethyl sulfoxide, benzene, diethyl ether, methylene chloride, 1,2-dichloroethane, sulfuric acid, fluorosulfonic acid, and hydrogen fluoride. The obtained values are absolute chemical standard potentials of the proton (pH=0 in this solvent). They are used to anchor the individual solvent specific acidity (pH) scales to our recently introduced absolute acidity scale.