DFT computational schemes for 1H and 13C NMR chemical shifts of natural products,exemplified by strychnine |
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Authors: | Valentin A. Semenov Leonid B. Krivdin |
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Affiliation: | A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia |
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Abstract: | A number of computational schemes based on different Density Functional Theory (DFT) functionals in combination with a number of basis sets were tested in the calculation of 1H and 13C NMR chemical shifts of strychnine, as a typical representative of the vitally important natural products, and used as a challenging benchmark and a rigorous test for such calculations. It was found that the most accurate computational scheme, as compared with experiment, was PBE0/pcSseg-4//pcseg-3 characterized by a mean absolute error of 0.07 ppm for the range of about 7 ppm for 1H NMR chemical shifts and that of only 1.13 ppm for 13C NMR chemical shifts spread over the range of about 150 ppm. For more practical purposes, including investigation of larger molecules from this series, a much more economical computational scheme, PBE0/pcSseg-2//pcseg-2, characterized by almost the same accuracy and much less computational demand, was recommended. |
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Keywords: | 1H and 13C NMR basis sets DFT functionals LDBS scheme strychnine |
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