title: MP2 calculation of (77) Se NMR chemical shifts taking into account relativistic corrections.
abstract: The main factors affecting the accuracy and computational cost of the Second-order Möller-Plesset perturbation theory (MP2) calculation of (77) Se 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 (77) Se 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 (77) Se 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 (77) Se NMR chemical shifts reaching 2500 ppm resulting in a mean absolute percentage error of 0.7%.
authors.affiliation: Siberian Branch of the Russian Academy of Sciences, A. E. Favorsky Irkutsk Institute of Chemistry, Favorsky St 1, Irkutsk, 664033, Russia.
authors.forename: Yury Yu
authors.initials: YY
authors.lastname: Rusakov
authors.affiliation: Siberian Branch of the Russian Academy of Sciences, A. E. Favorsky Irkutsk Institute of Chemistry, Favorsky St 1, Irkutsk, 664033, Russia.
authors.forename: Irina L
authors.initials: IL
authors.lastname: Rusakova
authors.affiliation: Siberian Branch of the Russian Academy of Sciences, A. E. Favorsky Irkutsk Institute of Chemistry, Favorsky St 1, Irkutsk, 664033, Russia.
authors.forename: Leonid B
authors.initials: LB
authors.lastname: Krivdin
keywords: 77Se NMR; GIAO-MP2; chemical shift; locally dense basis set; magnetic shielding constant; organoselenium compounds; relativistic effects