Effects of Quantum Nuclear Delocalisation on NMR Parameters from Path Integral Molecular Dynamics |
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| Authors: | Dr Martin Dra?ínský Dr Paul Hodgkinson |
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| Affiliation: | 1. Department of Chemistry, Durham University, South Road, DH1 3LE Durham (UK);2. Institute of Organic Chemistry and Biochemistry, Flemingovo nám. 2, 16610 Prague (Czech Republic) |
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| Abstract: | The influence of nuclear delocalisation on NMR chemical shifts in molecular organic solids is explored using path integral molecular dynamics (PIMD) and density functional theory calculations of shielding tensors. Nuclear quantum effects are shown to explain previously observed systematic deviations in correlations between calculated and experimental chemical shifts, with particularly large PIMD‐induced changes (up to 23 ppm) observed for carbon atoms in methyl groups. The PIMD approach also enables isotope substitution effects on chemical shifts and J couplings to be predicted in excellent agreement with experiment for both isolated molecules and molecular crystals. An approach based on convoluting calculated shielding or coupling surfaces with probability distributions of selected bond distances and valence angles obtained from PIMD simulations is used to calculate isotope effects. |
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| Keywords: | density functional calculations isotope effects NMR spectroscopy nuclear delocalisation path integral molecular dynamics |
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