Chemical Shift Tensors of Cimetidine Form A Modeled with DFT Calculations: Implications for NMR Crystallography.
Chemical Shift Tensors of Cimetidine Form A Modeled with DFT Calculations: Implications for NMR Crystallography.
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使用 DFT 计算建模的 A 型西咪替丁的化学位移张量：对 NMR 晶体学的影响。
DOI：
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发表时间：
2020
影响因子：
2.9
通讯作者：
R. Iuliucci
中科院分区：
文献类型：
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作者：
Sean T. Holmes;Olivia G Engl;Matthew N. Srnec;J. Madura;Rosalynn Quiñones;J. Harper;R. Schurko;R. Iuliucci
使用FIREMAT技术测量了活性药物成分西咪替丁A型的10个晶体学上不同的碳原子的13 C化学位移张量的主成分。利用密度泛函理论（DFT）计算了13C和15N磁屏蔽张量，并对13C和15N峰进行了归属。使用平面波和基于簇的方法对西咪替丁和有机晶体的训练集进行DFT计算。前一组计算允许采用几种结构细化策略，包括利用使用13 C和15 N磁屏蔽张量参数化的色散校正力场的计算。后一组计算的特点是使用资源密集型混合DFT方法计算磁屏蔽张量。使用新的力场修正的结构上的计算结果在15 N磁屏蔽张量的改进值（与实验化学位移张量的协议衡量），虽然在13 C屏蔽张量的预测几乎没有改善。13 C和15 N磁屏蔽张量的计算使用混合泛函显示出更好的协议与实验值相比，使用GGA泛函，独立的结构细化的方法，特别是提高了与氮键合的碳原子的屏蔽使用混合DFT方法。
The principal components of the 13C chemical shift tensors for the ten crystallographically distinct carbon atoms of the active pharmaceutical ingredient cimetidine Form A have been measured using the FIREMAT technique. Density functional theory (DFT) calculations of 13C and 15N magnetic shielding tensors are used to assign the 13C and 15N peaks. DFT calculations were performed on cimetidine and a training set of organic crystals using both plane-wave and cluster-based approaches. The former set of calculations allowed several structural refinement strategies to be employed, including calculations utilizing a dispersion-corrected force field that was parameterized using 13C and 15N magnetic shielding tensors. The latter set of calculations featured the use of resource-intensive hybrid-DFT methods for the calculation of magnetic shielding tensors. Calculations on structures refined using the new force field correction result in improved values of 15N magnetic shielding tensors (as gauged by agreement with experimental chemical shift tensors), although little improvement is seen in the prediction of 13C shielding tensors. Calculations of 13C and 15N magnetic shielding tensors using hybrid functionals show better agreement with experimental values in comparison to those using GGA functionals, independent of the method of structural refinement; the shielding of carbon atoms bonded to nitrogen are especially improved using hybrid DFT methods.