Ranking of DFT methods: B3LYP failed to provide 1JCH coupling constants, the best was mPW1PW91

What is it about?

Twelve DFT computational methods, namely different B3LYP approximations/basis sets, were evaluated to predict the 2.3JCH values of six densely oxygen-functionalized epoxy compounds. The pcJ-1 basis set thus selected was then used to statistically evaluate the 32 methods, namely density functional/pcJ-1, used to predict the aforementioned JCH values. In this comparative study of DFT functions, mPW1PW91 (first) and PBE0 were the best, and BP86 and BLYP (last) were the worst. Furthermore, the 1JCH data sets predicted by 11 different DFT methods were considered and compared with the experimental data measured for the epoxy compounds mentioned above.

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Why is it important?

The success of the very popular B3LYP/IGLO-II method, which has frequently been reported previously and partially also confirmed here, has been attributed to a very fortunate elimination of the inherent errors of this method. Consequently, its use should be abandoned in favor of other, more accurate DFT methods. In general, the methodology of the approximation mPW1PW91/pcJ-1//B3LYP/6-311+G(d,p) used with the IEF-PCM(UFF,CHCl3) solvation scheme is recommended to predict the nJCH values (n = 1-3) in different organic and bioorganic molecular systems.

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