Neutralization of 4-[(2,2,3,3-tetrafluoropropoxy)methyl]pyridine with hydrohalo acids HX (X = Cl and Br) yielded the pyridinium salts 4-[(2,2,3,3-tetrafluoropropoxy)methyl]pyridinium chloride, CHFNO·Cl, (1), and 4-[(2,2,3,3-tetrafluoropropoxy)methyl]pyridinium bromide, CHFNO·Br, (2), both carrying a fluorous side chain at the para position of the pyridinium ring. Single-crystal X-ray diffraction techniques revealed that (1) and (2) are isomorphous. The halide anions accept four hydrogen bonds from N-H, ortho-C-H and CF-H groups. Two cations and two anions form a centrosymmetric dimeric building block, utilizing complimentary N-H...X...H-Csp connections. These dimers are further crosslinked, utilizing another complimentary Csp-H...X...H-Csp connection. The pyridinium rings are π-stacked, forming columns running parallel to the a axis that make angles of ca 44-45° with the normal to the pyridinium plane. There are also supramolecular C-H...F-C interactions, namely bifurcated C-H...F and bifurcated C-F...H interactions; additionally, one type II C-F...F-C halogen bond has been observed.
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