An efficient DFT method of predicting the one-, two- and three-bond indirect spin-spin coupling constants involving a fluorine nucleus in fluoroalkanes

摘要

The values of the indirect nuclear spin-spin coupling constants for a series of aliphatic fluorocompounds have been calculated using DFT-based methods and compared with the experimental values of these parameters. The set of the molecular objects contained four fluoromethanes, five fluoroethanes, two fluorocyclopropanes, and eleven fluorocompounds containing either five-membered or six-membered rings. The effectiveness of three hybrid functionals, B3LYP, PBE0 and BHandH and three basis sets, 6-311++ G(2d, p) (s), 6-311++ G(3df, 3pd) (m) and aug-pcJ-3-2006 (l) has been checked. In order to compare the results concerning various types of coupling constants and obtained by various methods, a prediction-quality criterion has been proposed. It has been found that only the BHandH functional ensures calculating the proper values of one-bond fluorine-carbon and two-bond fluorine-fluorine coupling constants. For this functional application of the s basis, the smallest of the bases tested, has already yielded acceptable good results. The DFT BHandH/s PCM method has also provided the proper values of (n)J(F, H) (n = 1, 2, 3) and (n)J(F, C) (n = 2, 3) parameters. On the other hand, the analysis of the limited number of the results concerning (1)J(C, H) coupling constants has pointed out that in this case this method is less effective than the DFT PBE0/l PCM method.