Computational Protocols for the 19F NMR Chemical Shifts. Part 1: Methodological Aspects

The DFT calculation of F-19 NMR chemical shifts was performed for two benchmark compounds, perfluoroquinoline and perfluoroisoquinoline, each involving seven non-equivalent fluorine atoms, with using a variety of functionals and basis sets. Performed calculations provided a markedly good correlation of calculated fluorine chemical shifts with experiment. Best result was achieved for the BHandHLYP functional in combination with the quadruple zeta Jensen's segmented basis set pcSseg-3 characterized by a mean absolute error of 2.5 ppm in the range of about 120 ppm, corresponding to a 2% error in the percentage terms. Proposed computational protocol BHandHLYP/pcSseg-3 showed a remarkably good performance on a benchmark series of eight fluorinated condensed heteroaromatic compounds.