Weak hydrogen bonding and fluorous interactions in the chloride and bromide salts of 4‐[(2,2,3,3‐tetrafluoropropoxy)methyl]pyridinium

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, C₉H₁₀F₄NO⁺·Cl^?, (1), and 4‐(2,2,3,3‐tetrafluoropropoxy)methyl]pyridinium bromide, C₉H₁₀F₄NO⁺·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 CF₂—H groups. Two cations and two anions form a centrosymmetric dimeric building block, utilizing complimentary N—H…X …H—Csp ³ connections. These dimers are further crosslinked, utilizing another complimentary Csp ²—H…X …H—Csp ² 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.