Hersh William H, Chan Tsz-Yeung
Department of Chemistry and Biochemistry, Queens College, Queens, NY 11367-1597, USA.
Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, USA.
Beilstein J Org Chem. 2023 Jan 10;19:36-56. doi: 10.3762/bjoc.19.4. eCollection 2023.
Calculation of P NMR chemical shifts for a series of tri- and tetracoordinate phosphorus compounds using several basis sets and density functional theory (DFT) functionals gave a modest fit to experimental chemical shifts, but an excellent linear fit when plotted against the experimental values. The resultant scaling methods were then applied to a variety of "large" compounds previously selected by Latypov et al. and a set of stereoisomeric and unusual compounds selected here. No one method was best for all structural types. For compounds that contain P-P bonds and P-C multiple bonds, the Latypov et al. method using the PBE0 functional was best (mean absolute deviation/root mean square deviation (MAD/RMSD) = 6.9/8.5 ppm and 6.6/8.2 ppm, respectively), but for the full set of compounds gave higher deviations (MAD/RMSD = 8.2/12.3 ppm), and failed by over 60 ppm for a three-membered phosphorus heterocycle. Use of the M06-2X functional for both the structural optimization and NMR chemical shift calculation was best overall for the compounds without P-C multiple bonds (MAD/RMSD = 5.4/7.1 ppm), but failed by 30-49 ppm for compounds having any P-C multiple-bond character. Failures of these magnitudes have not been reported previously for these widely used functionals. These failures were then used to screen a variety of recommended functionals, leading to better overall methods for calculation of these chemical shifts: optimization with the M06-2X functional and NMR calculation with the PBE0 or ωB97x-D functionals gave values for MAD/RMSD = 6.9/8.5 ppm and 6.8/9.1 ppm, respectively, over an experimental chemical shift range of -181 to 356 ppm. Due to the unexplained failures observed, we recommend use of more than one method when looking at novel structures.
使用多种基组和密度泛函理论（DFT）泛函对一系列三配位和四配位磷化合物的³¹P NMR化学位移进行计算，结果与实验化学位移的拟合效果一般，但与实验值作图时呈现出出色的线性拟合。然后将所得的标度方法应用于Latypov等人先前选择的各种“大型”化合物以及此处选择的一组立体异构和特殊化合物。没有一种方法对所有结构类型都是最佳的。对于含有P-P键和P-C多重键的化合物，使用PBE0泛函的Latypov等人的方法是最佳的（平均绝对偏差/均方根偏差（MAD/RMSD）分别为6.9/8.5 ppm和6.6/8.2 ppm），但对于所有化合物组偏差更高（MAD/RMSD = 8.2/12.3 ppm），对于一个三元磷杂环，偏差超过60 ppm。对于没有P-C多重键的化合物，在结构优化和NMR化学位移计算中都使用M06-2X泛函总体上是最佳的（MAD/RMSD = 5.4/7.1 ppm），但对于具有任何P-C多重键特征的化合物，偏差为30 - 49 ppm。对于这些广泛使用的泛函，此前尚未报道过如此大的偏差。然后利用这些偏差来筛选各种推荐的泛函，从而得到计算这些化学位移的更好的总体方法：使用M06-2X泛函进行优化，使用PBE0或ωB97x-D泛函进行NMR计算，在-181至356 ppm的实验化学位移范围内，MAD/RMSD值分别为6.9/8.5 ppm和6.8/9.1 ppm。由于观察到无法解释的偏差，我们建议在研究新结构时使用不止一种方法。
