MP2 calculation of 77Se NMR chemical shifts taking into account relativistic corrections

The main factors affecting the accuracy and computational cost of the Second-order Moller-Plesset perturbation theory (MP2) calculation of Se-77 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 (192-198ppm) resulting in a total shielding relativistic correction of about 230-260ppm (some 15% of the total values of selenium absolute shielding constants). Diamagnetic term is practically constant, while paramagnetic contribution spans over 70-80ppm. In the Se-77 NMR chemical shifts scale, relativistic corrections are about 20-30ppm (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 Se-77 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 17ppm for the span of Se-77 NMR chemical shifts reaching 2500ppm resulting in a mean absolute percentage error of 0.7%. Copyright (C) 2015 John Wiley & Sons, Ltd.