Nuclear size and QED effects on NMR spectroscopic parametersNuclear size and QED effects on NMR spectroscopic parameters

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

Riviera Maya

Congreso; 37 Congreso internacional de Químicos Teóricos - QUITEL; 2011

The two most useful NMR spectroscopic parameters, the nuclear magnetic shielding, σ, and the indirect spin-spin coupling, J, are quite sensitive to local electronic environment. This is the reason why they are powerful sensors for getting reliable information on the whole molecular structure (electronic and geometric). In the last decade there was an extraordinary increase in the understanding of relativistic effects on molecular properties1, being that two spectroscopic parameters between the most influenced by such effects2,3. They can be so large that do produce the inversion of NR tendencies following experimental results, or convert diamagnetic shieldings in paramagnetic, for heavy elements. Then one can infer that the nuclear model one uses to describe the electron-nucleus interaction would be of importance in accurate calculations. Few years ago it was predicted that QED effects may be as large as of 1% of relativistic effects4. At the moment there is no any implementation that permits to verify whether this is the actual order of magnitude. In this presentation we will show recent advances in our studies of relativistic and QED effects on both NMR spectroscopic parameters. We will show that the effects of nuclear size and QED are as large that they must be included in accurate calculations. Preliminary values of QED effects on J-couplings will be exposed