Zhang Ying, Wu Anan, Xu Xin, Yan Yijing
State Key Laboratory of Physical Chemistry of Solid Surfaces, Center for Theoretical Chemistry, College for Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
J Phys Chem A. 2007 Sep 27;111(38):9431-7. doi: 10.1021/jp0740503. Epub 2007 Aug 14.
We perform a systematic investigation of how the B3LYP/6-311+G(2d,p) calculated 13C nuclear magnetic shielding constants depend on the 6-31G(d)-optimized geometries for a set of 18 molecules with various chemical environments. For absolute shieldings, the Hartree-Fock (HF)-optimized geometries lead to a mean absolute deviation (MAD) of 5.65 ppm, while the BLYP- and B3LYP-optimized geometries give MADs of 13.07 and 10.14 ppm, respectively. For chemical shifts, the HF, BLYP and B3LYP geometries lead to MADs of 2.36, 5.80, and 4.43 ppm, respectively. We find that the deshielding tendency of B3LYP can be effectively compensated by using the HF-optimized geometries. When we apply the B3LYP//HF protocol to versicolorin A and 5alpha-androstan-3,17-dione, MADs of 1.86 and 1.41 ppm, respectively, are obtained for chemical shifts, in satisfactory agreement with the experiment.
我们对一组18个具有不同化学环境的分子进行了系统研究，探究B3LYP/6 - 311 + G(2d,p)计算的13C核磁屏蔽常数如何依赖于6 - 31G(d)优化的几何结构。对于绝对屏蔽，Hartree - Fock（HF）优化的几何结构导致平均绝对偏差（MAD）为5.65 ppm，而BLYP和B3LYP优化的几何结构分别给出的MAD为13.07和10.14 ppm。对于化学位移，HF、BLYP和B3LYP几何结构分别导致MAD为2.36、5.80和4.43 ppm。我们发现，通过使用HF优化的几何结构，可以有效补偿B3LYP的去屏蔽趋势。当我们将B3LYP//HF方法应用于杂色曲菌素A和5α - 雄甾烷 - 3,17 - 二酮时，化学位移的MAD分别为1.86和1.41 ppm，与实验结果吻合良好。
