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首页> 外文期刊>Chemistry: A European journal >Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ~(183)W NMR Chemical Shifts
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Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of ~(183)W NMR Chemical Shifts

机译：通过〜（183）W NMR化学位移的相对论DFT计算对聚氧钨酸盐的计算模型

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摘要

The ~(183)W nuclear shielding in a variety of tungsten polyoxometalates (POM) (Lindqvist,Anderson,deca-tungstates,Keggin) of different shapes and charges has been modeled by DFT calculations that take into account relativistic effects,by means of the zero-order regular approximation (ZORA),and solvent effects,by the conductor-like screening model (COSMO) continuum method.The charge/surface area ratio (q/A) is proposed as an indicator of the charge density to which the sol-vation energies of all POMs are correlated in a satisfactory way.Among the various theoretical levels tested (ZORA scalar or spin-orbit,frozen-core or all-electron basis set,geometry optimization in the gas phase or in the continuum solvent,etc.),the best results are obtained when both geometry optimization in solvent and spin-orbit shielding are included (mean absolute error of delta=35 ppm).The quality of the computed chemical shifts depends systematically on the charge density as expressed by q/A;thus,POMs with low q/A ratios display the best agreement with experimental data.The performance of the method is such that computed values can aid the assignment of the ~(183)W NMR spectra of polyoxotungstates,as shown by the case of alpha-[PW_(11)TiO_(40)]~(5-),whose six signals are ranked computationally so as to almost reproduce the experimental ordering even though the signals are spaced by as little as 5 ppm.
机译：已经通过DFT计算对各种形状和电荷不同的多金属多金属钨酸盐（POM）（Lindqvist，Anderson，十钨酸盐，Keggin）中的〜（183）W核屏蔽进行了建模，该计算考虑了相对论效应，零序正则逼近（ZORA）和溶剂效应，采用类导体屏蔽模型（COSMO）连续介质方法。电荷/表面积比（q / A）被提出作为溶胶对电荷密度的指示所有POM的-v能量都以令人满意的方式关联。在测试的各种理论水平（ZORA标量或自旋轨道，冷冻核或全电子基集，气相或连续溶剂中的几何结构优化等）中），当同时包含溶剂和自旋轨道屏蔽的几何优化（均值绝对误差为delta = 35 ppm）时，可获得最佳结果。化学位移的计算系统取决于电荷密度，由q /表示A;因此，POM低q / A比值与实验数据显示出最佳一致性。该方法的性能是，计算值可以帮助分配多氧钨酸盐的〜（183）W NMR光谱，如alpha- [PW_（11 ）TiO_（40）]〜（5-），其六个信号在计算上进行排序，从而即使信号间距仅为5 ppm，也几乎可以重现实验顺序。

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