MOLECULAR AND CRYSTAL STRUCTURE OF (PYRAZIN- 1-IUM-1-YL)(PERFLUOROPYRIDIN-4-YL) AND (4,4′-BIPYRIDIN- 1-IUM-1-YL)(PERFLUOROPYRIDIN-4-YL)AMIDES
G. I. Borodkin, A. Y. Vorob'ev, Y. V. Gatilov
Keywords: N-imines of bipyridine and pyrazine, C-F-ПЂ interactions, ПЂ stacking, hydrogen bond, single crystal X-ray diffraction study, quantum chemical calculations
Pages: 967-972
Abstract
The single crystal X-ray diffraction study of (pyrazin-1-ium-1-yl)(perfluoropyridin-4-yl) and (4,4′-bipyridin)-1-ium-1-yl(perfluoropyridin-4-yl)amides is performed. In all cases, the N+-N- bond length is less than that of the single Nplanar.-Nplanar. bond, but considerably more than that of the double N=N bond, which indicates a weak involvement of the N- lone pair of the C5NF4N- group in conjugation with pyrazine or bipyridine moieties. Quantum chemical calculations by DFT/(PBE/L1), B3LYP/L1, and RI-MP2/L1 methods provide the geometry of amides similar to the experimental one. Crystals of (pyrazin-1-ium-1-yl)(perfluoropyridin-4-yl)amide form stacks mainly through F-π interactions. The stacks are joined in 3D architecture by weak C-H…N and C-H…F hydrogen bonds. In the case of (4,4′-bipyridin)-1-ium-1-yl(perfluoropyridin-4-yl)amide crystals, an essential role is played by the π stacking interactions of heteroaromatic rings.
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