Accurate Calculation of Solvation Free Energies in Supercritical Fluids by Fully Atomistic Simulations: Probing the Theory of Solutions in Energy Representation,Journal of Chemical Theory and Computation

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Accurate Calculation of Solvation Free Energies in Supercritical Fluids by Fully Atomistic Simulations: Probing the Theory of Solutions in Energy Representation
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2015-04-29 00:00:00 , DOI: 10.1021/acs.jctc.5b00172
Andrey I. Frolov ₁

Affiliation

Accurate calculation of solvation free energies (SFEs) is a fundamental problem of theoretical chemistry. In this work we perform a careful validation of the theory of solutions in energy representation (ER method) developed by Matubayasi et al. [J. Chem. Phys.2000, 113, 6070–6081] for SFE calculations in supercritical solvents. This method can be seen as a bridge between the molecular simulations and the classical (not quantum) density functional theory (DFT) formulated in energy representation. We performed extensive calculations of SFEs of organic molecules of different chemical natures in pure supercritical CO₂ (sc-CO₂) and in sc-CO₂ with addition of 6 mol % of ethanol, acetone, and n-hexane as cosolvents. We show that the ER method reproduces SFE data calculated by a method free of theoretical approximations (the Bennett’s acceptance ratio) with the mean absolute error of only 0.05 kcal/mol. However, the ER method requires by an order less computational resources. Also, we show that the quality of ER calculations should be carefully monitored since the lack of sampling can result into a considerable bias in predictions. The present calculations reproduce the trends in the cosolvent-induced solubility enhancement factors observed in experimental data. Thus, we think that molecular simulations coupled with the ER method can be used for quick calculations of the effect of variation of temperature, pressure, and cosolvent concentration on SFE and hence solubility of bioactive compounds in supercritical fluids. This should dramatically reduce the burden of experimental work on optimizing solvency of supercritical solvents.

中文翻译：

完全原子模拟精确计算超临界流体中的无溶剂化能：探索能量表示中的溶液理论

溶剂化自由能（SFEs）的准确计算是理论化学的基本问题。在这项工作中，我们对Matubayasi等人开发的能量表示（ER方法）解决方案理论进行了仔细的验证。[ J. Chem。物理 2000，113，6070-6081]用于在超临界溶剂SFE计算。该方法可以看作是分子模拟与以能量表示形式表达的经典（非量子）密度泛函理论（DFT）之间的桥梁。我们对纯化学超临界CO ₂（sc-CO ₂）和sc-CO ₂中不同化学性质的有机分子的SFE进行了广泛的计算，并添加了6 mol％的乙醇，丙酮和ñ -己烷作为助溶剂。我们表明ER方法可重现通过无理论方法计算出的SFE数据近似值（贝内特的验收率），平均绝对误差仅为0.05 kcal / mol。但是，ER方法按顺序需要较少的计算资源。此外，我们表明，应仔细监控ER计算的质量，因为缺乏采样会导致预测结果出现明显偏差。本计算重现了在实验数据中观察到的助溶剂诱导的溶解度增强因子的趋势。因此，我们认为结合ER方法的分子模拟可用于快速计算温度，压力和助溶剂浓度变化对SFE的影响，从而快速计算生物活性化合物在超临界流体中的溶解度。这将大大减轻优化超临界溶剂溶解度的实验工作负担。

更新日期：2015-04-29

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