预测 PFAS 的 19F NMR 化学位移和与 PFAS 结构的连接的计算协议,Journal of Computational Chemistry

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预测 PFAS 的 19F NMR 化学位移和与 PFAS 结构的连接的计算协议
Journal of Computational Chemistry ( IF 3.4 ) Pub Date : 2022-06-06 , DOI: 10.1002/jcc.26939
Maleigh Mifkovic ₁ , Jessica Pauling ₁ , Shubham Vyas ₁

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全氟烷基物质和多氟烷基物质 (PFAS) 是强大的“永久”化学品，由于无法使用传统技术降解，因此已成为全球环境污染物。除了 PFAS 的持久性之外，PFAS 的结构和功能多样性给识别和修复带来了独特的挑战。由于许多 PFAS 缺乏标准，它们的识别更加复杂。这项工作旨在开发一种用于计算和建立准确的协议¹⁹使用密度泛函理论 (DFT) 对 PFAS 进行 F NMR 化学位移，这有助于识别 PFAS。通过将计算数据与实验测量值进行比较来评估溶剂化和基组的影响。结果表明，在方法中添加色散校正可将计算的 NMR 参数的准确性提高到实验值的 4 ppm 以内。添加第二个漫反射函数和额外的极化并没有提高精度，可能是因为氟的电负性不允许氟原子的电子密度被极化。包含各种隐式溶剂化（DMSO、氯仿和水）在准确度上的差异可以忽略不计，并且总体上不如气相计算准确。然后将最准确的方法应用于更环保的 PFAS，并评估螺旋性质对 NMR 特征的影响。这项工作的意义在于能够使用以下方法改进结构多样化 PFAS 的识别¹⁹ F 核磁共振。

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Computational protocol for predicting 19F NMR chemical shifts for PFAS and connection to PFAS structure

Per- and polyfluoroalkyl substances (PFAS) are robust “forever” chemicals that have become global environmental contaminants due to their inability to degrade using traditional techniques. In addition to the persistent nature of PFAS, the structural and functional diversity in PFAS creates a unique challenge in identification and remediation. Their identification is further complicated by the absence of standards for many PFAS. This work is aimed at developing a protocol for computing and establishing accurate ¹⁹F NMR chemical shifts for PFAS using density functional theory (DFT), which can aid in the identification of PFAS. The impact of solvation and basis sets was evaluated by comparing the computed data with the experimental measurements. Results showed the addition of dispersion corrections in the methodology improve the accuracy of calculated NMR parameters within 4 ppm of the experimental values. Adding a second diffuse function and additional polarization did not improve the accuracy, likely because of the electronegativity of fluorine which does not allow the electron density of fluorine atoms to be polarized. The inclusion of various implicit solvation (DMSO, chloroform, and water) yielded negligible differences in accuracy, and were overall less accurate than the gas phase calculations. The most accurate methodology was then applied to more environmentally relevant PFAS, and the impact of helical nature on the NMR signatures was evaluated. The implication of this work is to be able to improve the identification of structurally diverse PFAS using the ¹⁹F NMR.

更新日期：2022-06-06

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