Issue 46, 2019

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

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

Supplementary files

Article information

Article type
Paper
Submitted
12 авг 2019
Accepted
17 окт 2019
First published
18 окт 2019

CrystEngComm, 2019,21, 7085-7093

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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