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Towards Accurate Predictions of Proton NMR Spectroscopic Parameters in Molecular Solids
Author(s) -
Dračínský Martin,
Vícha Jan,
Bártová Kateřina,
Hodgkinson Paul
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000629
Subject(s) - chemical shift , proton , chemistry , molecular dynamics , proton nmr , magic angle spinning , computational chemistry , molecule , density functional theory , nuclear magnetic resonance spectroscopy , chemical physics , physics , stereochemistry , organic chemistry , quantum mechanics
Abstract The factors contributing to the accuracy of quantum‐chemical calculations for the prediction of proton NMR chemical shifts in molecular solids are systematically investigated. Proton chemical shifts of six solid amino acids with hydrogen atoms in various bonding environments (CH, CH 2 , CH 3 , OH, SH and NH 3 ) were determined experimentally using ultra‐fast magic‐angle spinning and proton‐detected 2D NMR experiments. The standard DFT method commonly used for the calculations of NMR parameters of solids is shown to provide chemical shifts that deviate from experiment by up to 1.5 ppm. The effects of the computational level (hybrid DFT functional, coupled‐cluster calculation, inclusion of relativistic spin‐orbit coupling) are thoroughly discussed. The effect of molecular dynamics and nuclear quantum effects are investigated using path‐integral molecular dynamics (PIMD) simulations. It is demonstrated that the accuracy of the calculated proton chemical shifts is significantly better when these effects are included in the calculations.

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