Computation of 31P NMR chemical shifts in Keggin-based lacunary polyoxotungstates.
Computation of 31P NMR chemical shifts in Keggin-based lacunary polyoxotungstates.
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基于 Keggin 的空位多钨酸盐中 31P NMR 化学位移的计算。
DOI：
10.1039/d3dt02694a
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发表时间：
2024
期刊：
影响因子：
--
通讯作者：
Thompson JA
中科院分区：
文献类型：
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作者：
Thompson JA
采用密度泛函理论（DFT）计算系统地研究了各种交换相关泛函在再现实验31P核磁共振化学位移中的准确性，Keggin， [PW12O40]3−和相应的空白簇：[PW11O39]7−，[A-PW9O34]9−和[B-PW9O34]9−的δExp（31P）。最初，计算化学位移，δCalc（31P）在没有中和它们的电荷的情况下得到，其中相关误差δError（31P）作为harree - fock （HF）交换的函数减小，归因于P-O四面体的收缩。通过比较，δCalc（31P）与明确定位的反离子进行，使系统电荷中性，减少了差异，δError（31P）减少了1-2 ppm。然而，δCalc（31P）的不确定性仍然存在，特别是对于[B-PW9O34]9−阴离子，归因于反离子与中心四面体之间的直接静电相互作用。采用PBE/TZP//PBE0/TZP方法可获得最佳结果，平均绝对误差（MAE）和均方误差（MSE）为4.03 ppm。我们的研究结果强调，了解电解质和溶剂环境的性质对于获得理论和实验结果之间的合理一致至关重要。
Density Functional Theory (DFT) calculations were employed to systematically study the accuracy of various exchange-correlation functionals in reproducing experimental 31P NMR chemical shifts, δExp(31P) for Keggin, [PW12O40]3− and corresponding lacunary clusters: [PW11O39]7−, [A-PW9O34]9−, and [B-PW9O34]9−. Initially, computed chemical shifts, δCalc(31P) were obtained with without neutralising their charge in which associated error, δError(31P), decreased as a function of Hartree–Fock (HF) exchange, attributed to constriction of the P–O tetrahedron. By comparison, δCalc(31P) performed with explicitly located counterions to render the system charge neutral, reduced discrepancies, δError(31P) by 1–2 ppm. However, uncertainties in δCalc(31P) remain, particularly for [B-PW9O34]9− anions attributed to direct electrostatic interactions between the counterions and the central tetrahedron. Optimal results were achieved using the PBE/TZP//PBE0/TZP method, achieving a mean absolute error (MAE) and a mean squared error (MSE) of 4.03 ppm. Our results emphasize that understanding the nature of the electrolyte and solvent environment is essential to obtaining reasonable agreement between theoretical and experimental results.