Scaling factors for carbon NMR chemical shifts obtained from DFF B3LYP calculations
Scaling factors for carbon NMR chemical shifts obtained from DFF B3LYP calculations
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DOI：
10.1016/j.theochem.2008.09.021
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发表时间：
2009-01-15
影响因子：
--
通讯作者：
Zhou, Shen
中科院分区：
文献类型：
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作者：
Aliev, Abil E.;Courtier-Murias, Denis;Zhou, Shen
使用计算的化学位移的线性比例来提高DFT预测的(13)C NMR化学位移的准确性，选择了广泛应用的使用B3LYP/6-3G(d)优化几何结构的GIAO B3LYP/6-311+G(2d,p)方法，该方法可以经济有效地计算具有100个及更多原子的分子系统中的13C化学位移。使用针对具有不同官能团的22个简单分子通过实验确定的一组27 13C NMR化学位移以确定用于再现(13)C化学位移的实验测量值的缩放因子。结果表明，使用简单的关系（delta(scale) = 0.95 delta(calc) + 0.30，其中 delta(calc) 和 5(scalc) 分别是计算的 (13)C 和化学位移的线性缩放值）可以将所考虑的 27 个化学位移的平均绝对偏差提高三倍。为了测试推导的缩放因子的普遍适用性，我们使用复杂的有机分子（例如紫杉醇和类固醇）来证明 DFT 预测化学位移的准确性显着提高。该方法还优于最近推荐的用于 GIAO B3LYP/6-311+G(2d,p) 计算 (13)C 化学位移的 Hartree-Fock 优化几何结构。 (C) 2008 Elsevier B.V. 保留所有权利。
A linear scaling of the calculated chemical shifts is used in order to improve the accuracy of the DFT predicted (13)C NMR chemical shifts, The widely applied method of GIAO B3LYP/6-311+G(2d,p) using the B3LYP/6-3G(d) optimized geometries is chosen, which allows cost-effective calculations of the 13C chemical shifts in the molecular systems with 100 and more atoms. A set of 27 13C NMR chemical shifts determined experimentally for 22 simple molecules with various functional groups is used in order to determine scaling factors for reproducing experimentally measured values of (13)C chemical shifts. The results show that the use of a simple relationship (delta(scale) = 0.95 delta(calc) + 0.30, where delta(calc) and 5(scalc) are the (13)C calculated and the linearly scaled values of the chemical shifts, respectively) allows to achieve a three-fold improvement in mean absolute deviations for 27 chemical shifts considered. To test the universal applicability of the scaling factors derived, we have used complex organic molecules such as taxol and a steroid to demonstrate the significantly improved accuracy of the DFT predicted chemical shifts. This approach also outperforms the recently recommended usage of the Hartree-Fock optimized geometries for the GIAO B3LYP/6-311+G(2d,p) calculations of the (13)C chemical shifts. (C) 2008 Elsevier B.V. All rights reserved.