MP2 calculation of 77Se NMR chemical shifts taking into account relativistic corrections |
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| Authors: | Yury Yu. Rusakov Irina L. Rusakova Leonid B. Krivdin |
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| Affiliation: | Siberian Branch of the Russian Academy of Sciences, A. E. Favorsky Irkutsk Institute of Chemistry, Irkutsk, Russia |
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| Abstract: | The main factors affecting the accuracy and computational cost of the Second‐order Möller‐Plesset perturbation theory (MP2) calculation of 77Se NMR chemical shifts (methods and basis sets, relativistic corrections, and solvent effects) are addressed with a special emphasis on relativistic effects. For the latter, paramagnetic contribution (390–466 ppm) dominates over diamagnetic term (192–198 ppm) resulting in a total shielding relativistic correction of about 230–260 ppm (some 15% of the total values of selenium absolute shielding constants). Diamagnetic term is practically constant, while paramagnetic contribution spans over 70–80 ppm. In the 77Se NMR chemical shifts scale, relativistic corrections are about 20–30 ppm (some 5% of the total values of selenium chemical shifts). Solvent effects evaluated within the polarizable continuum solvation model are of the same order of magnitude as relativistic corrections (about 5%). For the practical calculations of 77Se NMR chemical shifts of the medium‐sized organoselenium compounds, the most efficient computational protocols employing relativistic Dyall's basis sets and taking into account relativistic and solvent corrections are suggested. The best result is characterized by a mean absolute error of 17 ppm for the span of 77Se NMR chemical shifts reaching 2500 ppm resulting in a mean absolute percentage error of 0.7%. Copyright © 2015 John Wiley & Sons, Ltd. |
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| Keywords: | 77Se NMR chemical shift magnetic shielding constant GIAO‐MP2 locally dense basis set relativistic effects organoselenium compounds |
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