title: Weak hydrogen bonding and fluorous interactions in the chloride and bromide salts of 4-[(2,2,3,3-tetrafluoropropoxy)methyl]pyridinium.
abstract: 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-Csp3connections. These dimers are further crosslinked, utilizing another complimentary Csp2-H...X...H-Csp2connection. 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.
authors.affiliation: Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan.
authors.forename: Norman
authors.initials: N
authors.lastname: Lu
authors.affiliation: Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan.
authors.forename: Rong Jyun
authors.initials: RJ
authors.lastname: Wei
authors.affiliation: Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan.
authors.forename: Kwan Yu
authors.initials: KY
authors.lastname: Lin
authors.affiliation: Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan.
authors.forename: Mani
authors.initials: M
authors.lastname: Alagesan
authors.affiliation: Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Yuh Sheng
authors.initials: YS
authors.lastname: Wen
authors.affiliation: Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 106, Taiwan.
authors.forename: Ling Kang
authors.initials: LK
authors.lastname: Liu
keywords: crystal structure; halogen bonding; hydrogen-bonding network; isomorphous structure; pyridinium salt; supramolecular interaction; weak fluorous interaction