Efficient prediction of nucleus independent chemical shifts for polycyclic aromatic hydrocarbons
Nuclear Magnetic Resonance (NMR) is one of the most powerful experimental techniques to characterize the structure of molecules and confined liquids. Nevertheless, the complexity of the systems under investigation usually requires complementary computational studies to interpret the NMR results. In...
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Published in | Physical chemistry chemical physics : PCCP Vol. 22; no. 24; pp. 13746 - 13755 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Cambridge
Royal Society of Chemistry
24.06.2020
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Subjects | |
Online Access | Get full text |
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Summary: | Nuclear Magnetic Resonance (NMR) is one of the most powerful experimental techniques to characterize the structure of molecules and confined liquids. Nevertheless, the complexity of the systems under investigation usually requires complementary computational studies to interpret the NMR results. In this work we focus on polycyclic aromatic hydrocarbons (PAHs), an important class of organic molecules which have been commonly used as simple analogues for the spectroscopic properties of more complex systems, such as porous disordered carbons. We use Density Functional Theory (DFT) to calculate
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C chemical shifts and Nucleus Independent Chemical Shifts (NICS) for 34 PAHs. The results show a clear molecular size dependence of the two quantities, as well as the convergence of the
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C NMR shifts towards the values observed for graphene. We then present two computationally cheap models for the prediction of NICS in simple PAHs. We show that while a simple dipolar model fails to produce accurate values, a perturbative tight-binding approach can be successfully applied for the prediction of NICS in this series of molecules, including some non-planar ones containing 5- and 7-membered rings. This model, one to two orders of magnitude faster than DFT calculations, is very promising and can be further refined in order to study more complex systems.
Predicted
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DFT isotropic NICS for anthracene, calculated on a grid of points around the molecule. |
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Bibliography: | 13 Electronic supplementary information (ESI) available: Comparison of chemical shifts calculated using DFT with different basis sets, visualizations of the grid points for which NICS are determined and of the dipolar model geometrical parameters, isotropic NICS for coronoids at a distance of 3 Å from the molecule center C chemical shifts, and detailed results for the dipolar and tight-binding models for the two cutoffs selected. See DOI 10.1039/d0cp01705a ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1463-9076 1463-9084 |
DOI: | 10.1039/d0cp01705a |