On the calculation of ¹⁵N chemical shifts using linear regression formulae. A performance comparison of different methods

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• 作者：Carlos A. Franca ; Reinaldo Pis Diez ; Alicia H. Jubert
• 关键词：NMR chemical shifts ; Linear regression formulae ; Density functional theory
• 刊名：Journal of Molecular Structure: THEOCHEM
• 出版年：2008
• 出版时间：15 May 2008
• 年：2008
• 卷：856
• 期：1-3
• 页码：1-8
• 全文大小：221 K

文摘

The calculation of NMR chemical shifts using linear regression formulae is revisited in the present work. ¹⁵N chemical shifts are considered as a test case. Mean unsigned errors of 4.8, 5.4 and 7.6 ppm are found for the B3LYP/6–31G(d)//B3LYP/6–31G(d), B3LYP/6–311+G(2d,p)//B3LYP/6–31G(d) and HF/6–31G(d)//B3LYP/6–31G(d) levels of theory, respectively, which are much more accurate than chemical shifts calculated by subtracting theoretical magnetic isotropic shieldings from the reference nitromethane. Moreover, the economical HF/6–31G(d)//B3LYP/6–31G(d) method is found to be about 15 times faster than the rather expensive B3LYP/6–311+G(2d,p)//B3LYP/6–31G(d) level of theory but only 2.5 times faster than B3LYP/6–31G(d)//B3LYP/6–31G(d). Our results indicate that the B3LYP/6–31G(d)//B3LYP/6–31G(d) level of theory constitutes an adequate compromise between accuracy and computational cost for ¹⁵N chemical shifts calculation using a linear regression formula.