RELATIVISTIC AND ELECTRON CORRELATION EFFECTS ON NMR PARAMETERS OF SN AND PB CONTAINING MOLECULES

ALEJANDRO MALDONADO; GUSTAVO A. AUCAR; CARLOS A. GIMENEZ

Castellón de la Plana

Congreso; Electronic structure: Principles and applications; 2016

Comité local

We analize the influence of relativistic and electron correlation effects on NMR parameters in the following set of heavy-atom containing molecules: XY4 (X = Sn, Pb; Y = H, F, Cl, Br, I). We applied two formalisms, the relativistic polarization propagator approach1 at random phase level of approach (RelPPA-RPA) and density functional theory (DFT) with different functionals as implemented in the DIRAC code. We have chosen different functionals that have different amount of HF exchange (PBE0, B3LYP, BLYP, BP86 for J-coupling calculation plus KT2 and KT3 for nuclear magnetic shielding). The nuclear magnetic shileding calculations are closer to experimental values as compared to those obtained applying the different functionals2. We argue about why those DFT functionals must be modified in order to obtain more accurate results of NMR magnetic shieldings within the relativistic regime: first, there is a dependence among both electron-correlation and relativistic effects that should be introduced in some way in the functionals; and second, the DIRAC code uses standard nonrelativistic functionals and the functionals B3LYP and PBE0 were parameterised only with data taken from light elements. It can explain why they are not able to properly introduce relativistic effects on nuclear magnetic shieldings. For those molecular systems, results of J-coupling calculations with B3LYP functional have the best performance as compared with available experimental data3. As for magnetic shieldings, DFT functionals must be modified in order to get reliable results for calculations of NMR J-coupling within the relativistic regime. We can state that there is a non-linear dependence among both, electron correlation and relativistic effects that should be introduced in the functionals. This can explain why they are not able to properly introduce relativistic effects on NMR parameters.References1. G. A. Aucar, R. H. Romero and A. F. Maldonado, Int. Rev. Phys. Chem., 2010, 29, 1.2. A. F. Maldonado and G. A. Aucar, J. Phys. Chem. A, 2014, 118, 7863.3. C. A. Gimenez, A. F. Maldonado and G. A. Aucar, Theor. Chem. Acc., 2015, Submitted.