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Issue 31, 2016
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Benchmark fragment-based 1H, 13C, 15N and 17O chemical shift predictions in molecular crystals

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Abstract

The performance of fragment-based ab initio1H, 13C, 15N and 17O chemical shift predictions is assessed against experimental NMR chemical shift data in four benchmark sets of molecular crystals. Employing a variety of commonly used density functionals (PBE0, B3LYP, TPSSh, OPBE, PBE, TPSS), we explore the relative performance of cluster, two-body fragment, and combined cluster/fragment models. The hybrid density functionals (PBE0, B3LYP and TPSSh) generally out-perform their generalized gradient approximation (GGA)-based counterparts. 1H, 13C, 15N, and 17O isotropic chemical shifts can be predicted with root-mean-square errors of 0.3, 1.5, 4.2, and 9.8 ppm, respectively, using a computationally inexpensive electrostatically embedded two-body PBE0 fragment model. Oxygen chemical shieldings prove particularly sensitive to local many-body effects, and using a combined cluster/fragment model instead of the simple two-body fragment model decreases the root-mean-square errors to 7.6 ppm. These fragment-based model errors compare favorably with GIPAW PBE ones of 0.4, 2.2, 5.4, and 7.2 ppm for the same 1H, 13C, 15N, and 17O test sets. Using these benchmark calculations, a set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided and their robustness assessed using statistical cross-validation. We demonstrate the utility of these approaches and the reported scaling parameters on applications to 9-tert-butyl anthracene, several histidine co-crystals, benzoic acid and the C–nitrosoarene SnCl2(CH3)2(NODMA)2.

Graphical abstract: Benchmark fragment-based 1H, 13C, 15N and 17O chemical shift predictions in molecular crystals

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Supplementary files

Article information


Submitted
18 Mar 2016
Accepted
11 Jul 2016
First published
19 Jul 2016

This article is Open Access

Phys. Chem. Chem. Phys., 2016,18, 21686-21709
Article type
Paper
Author version available

Benchmark fragment-based 1H, 13C, 15N and 17O chemical shift predictions in molecular crystals

J. D. Hartman, R. A. Kudla, G. M. Day, L. J. Mueller and G. J. O. Beran, Phys. Chem. Chem. Phys., 2016, 18, 21686
DOI: 10.1039/C6CP01831A

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