1H and 19F NMR chemical shifts for hydrogen bond strength determination: Correlations between experimental and computed values

TLDR: In this paper , the titration method based on 19 F NMR spectroscopy was performed for detecting and quantifying the formation of very weak hydrogen bond complexes such as those involving fluorine atoms as hydrogen bond acceptors.

Abstract: • 1 H and 19 F NMR chemical shifts of different hydrogen bond donors in the presence of hydrogen bond acceptors are highly correlated with each other and with several experimental and ab initio computed quantities. • The high sensitivity of 19 F NMR chemical shift to the electronic environment allows the detection of very weak hydrogen bond complexes and their strength determination. • 19 F NMR evidence for the formation in solution of an intermolecular hydrogen bond complex involving aromatic fluorine as hydrogen bond acceptor is reported. 1 H and 19 F NMR methods based on chemical shift measurements of different hydrogen bond donors used for quantifying hydrogen bond strength were analyzed and compared. The extracted values from these different methods are shown to be highly correlated with each other and with several experimental and ab initio computed quantities characterizing hydrogen bond formation. The titration method based on 19 F NMR spectroscopy was performed for detecting and quantifying the formation of very weak hydrogen bond complexes such as those involving fluorine atoms as hydrogen bond acceptors. This approach represents a powerful and reliable method for studying and characterizing these complexes that, although weak, are very relevant.