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Issue 46, 2019
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Halogen bonding in 5-iodo-1-arylpyrazoles investigated in the solid state and predicted by solution 13C-NMR spectroscopy

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Abstract

X-ray crystallography revealed the presence of halogen bonding in the crystal supramolecular structure of three highly substituted 1-arylpyrazoles. However the compounds 1–3 present different halogen bonding motifs that feature C–I⋯N (1), C–I⋯O (2) and C–I⋯π (3) contacts respectively. The magnitudes of the σ-hole corresponding to the iodine atom in the 5-iodo-1-arylpyrazoles 1–3 were calculated by DFT methods and the importance of halogen bonding as a significant stabilizing force within the crystal lattice was evaluated. The halogen bonding of 1-aryl-5-iodopyrazoles with several Lewis bases (Et3N, pyridine, DABCO or DMSO) was investigated by 13C NMR spectroscopy in the solution phase to confirm the halogen bonding affinity of the iodine atom. The most suitable reporting atom for the formation of the halogen bond is C-5 of the pyrazole ring, which is directly bonded to the iodine atom. The C-5 atom is significantly deshielded by as much as 6–7 ppm upon interaction with the Lewis bases in solution revealing the strong halogen bonding character of the iodine atom attached to C-5 of the pyrazole ring.

Graphical abstract: Halogen bonding in 5-iodo-1-arylpyrazoles investigated in the solid state and predicted by solution 13C-NMR spectroscopy

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Supplementary files

Article information


Submitted
12 Aug 2019
Accepted
17 Oct 2019
First published
18 Oct 2019

CrystEngComm, 2019,21, 7085-7093
Article type
Paper

Halogen bonding in 5-iodo-1-arylpyrazoles investigated in the solid state and predicted by solution 13C-NMR spectroscopy

M. M. Popa, I. C. Man, C. Draghici, S. Shova, M. R. Caira, F. Dumitrascu and D. Dumitrescu, CrystEngComm, 2019, 21, 7085 DOI: 10.1039/C9CE01263J

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