Theoretical calculations of 1H NMR chemical shifts for nitrogenated compounds in chloroform solution

In this work we report DFT and MP2 H-1 NMR calculations using the GIAO method and TMS as reference, for a series of nitrogenated compounds in chloroform solution to assess the ability of available theoretical models to reproduce experimental H-1 NMR spectra measured in CDCl3 solution, focusing on CHn and N-H proton signals which are relevant in conformational analysis studies. The Polarizable Continuum Model (PCM) may not work successfully to predict N-H chemical shifts in solution. Only when a few explicit solvent molecules are used in DFT-PCM-CHCl3 geometry optimizations a good agreement with experimental N-H chemical shifts measured in solution is reached, indicating that this is a reliable computational procedure for the prediction of the full NMR spectra of organic molecules containing N-H group. However, finding adequate DFT optimized solvated solute structures which reproduce well both N-H and CHn proton NMR signals can become a hard-computational task.