Details

Autor(en) / Beteiligte

• Adamson, Jasper
• Nazarski, Ryszard B.
• Jarvet, Jüri
• Pehk, Tõnis
• Aav, Riina

Titel

Shortfall of B3LYP in Reproducing NMR JCH Couplings in Some Isomeric Epoxy Structures with Strong Stereoelectronic Effects: A Benchmark Study on DFT Functionals

Ist Teil von

• Chemphyschem, 2018-03, Vol.19 (5), p.631-642

Ort / Verlag

Weinheim: Wiley Subscription Services, Inc

Erscheinungsjahr

2018

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Unprecedented scatter plots of calculated versus measured NMR 2,3JCH coupling constants in six densely oxygen functionalized epoxides are found with some B3LYP protocols, an effect attributed to stereoelectronic effects. Hence, 26 other exchange‐correlation density functionals (xc DFs) are benchmarked in this work. Very good results are achieved with mPW1PW91 and PBE0 in conjunction with the pcJ‐1 basis set (BS) of moderate size. A thorough statistical analysis of 53 relationships between the predicted and observed 2,3JCH datasets is presented. The effects of some xc DFs, including their x and c parts, and BSs on the calculation results are discussed, also in the context of DFT modeling of electron‐density distributions. Moreover, related 1JCH datasets predicted with 11 different DF methods are considered and compared with the experimental data. Finally, some proposals for further improvement of existing DFs based on the available nJCH (n=1–3) values are briefly outlined, in line with recent results on the DFT electron densities. Accuracy assessment: Reliable prediction of NMR parameters is crucial for conformation analysis of (bio)organic systems. The accuracy of 53 DFT methods (embracing 27 functionals and up to nine NMR‐specialized basis sets) in calculations of coupling constants is benchmarked against 225 experimental nJCH (n=1–3) values of six diastereomeric tricyclic epoxides in CDCl3 solution (see figure).