Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81Br NQR to characterize the electronic changes in the C–Br⋯N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance (dBr⋯N). Notably, 79/81Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81Br NQR resonances.

79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies

Cerreia Vioglio, P.;Chierotti, M. R.;Gobetto, R.;
2018

Abstract

Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81Br NQR to characterize the electronic changes in the C–Br⋯N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance (dBr⋯N). Notably, 79/81Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81Br NQR resonances.
9
20
4555
4561
http://pubs.rsc.org/en/journals/journal/sc
https://pubs.rsc.org/en/Content/ArticleLanding/2018/SC/C8SC01094C#!divAbstract
Chemistry (all), NMQ, SSNMR, Halogen bond, cweak interactions, crystal engineering
Cerreia Vioglio, P.; Szell, P.M.J.; Chierotti, M.R.; Gobetto, R.; Bryce, D.L.*
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/1687745
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