A computational tool to accurately and quickly predict 19F NMR chemical shifts of molecules with fluorine-carbon and fluorine-boron bonds

Abstract

We report the evaluation of density-functional-theory (DFT) based procedures for predicting 19F NMR chemical shifts at modest computational cost for a range of molecules with fluorine bonds, to be used as a tool for assisting the characterisation of reaction intermediates and products and as an aid to identifying mechanistic pathways. The results for a balanced learning set of molecules were then checked using two further testing sets, resulting in the recommendation of the ωB97XD/aug-cc-pvdz DFT method and basis set as having the best combination of accuracy and computational time, with a RMS error of 3.57 ppm. Cationic molecules calculated without counter-anion showed normal errors, whilst anionic molecules showed larger errors, possibly due to omission of the counter-cation. The method was applied to the prediction of the conformationally averaged 19F chemical shifts of 2,2,3,3,4,4,5,5-octafluoropentan-1-ol, in which gauche stereoelectronic effects involving fluorine dominate and to determining the position of coordination equilibria of fluorinated boranes as an aid to verifying the relative energies of intermediate species involved in catalytic amidation reactions involving boron catalysts.

A computational tool to accurately and quickly predict19F NMR chemical shifts of molecules with fluorine–carbon and fluorine–boron bonds

“…The list of solvents that were used as well as their calculated reference shielding constant can be found in the data repository collections. 55 The list of the molecules we selected, their solvent, as well as their experimental chemical shifts can be found in Table 1:…”

“…All the computational input and output files and experimental NMR primary datasets can be found as a FAIR data repository collection 55 and in associated sub-collections.…”