title: Structural comparison of three N-(4-halogenophenyl)-N'-[1-(2-pyridyl)ethylidene]hydrazine hydrochlorides.
abstract: 2-{1-[(4-Chloroanilino)methylidene]ethyl}pyridinium chloride methanol solvate, C(13)H(13)ClN(3)(+) x Cl(-) x CH(3)OH, (I), crystallizes as discrete cations and anions, with one molecule of methanol as solvent in the asymmetric unit. The N-C-C-N torsion angle in the cation indicates a cis conformation. The cations are located parallel to the (\overline{2}02) plane and are connected through hydrogen bonds by a methanol solvent molecule and a chloride anion, forming zigzag chains in the direction of the b axis. The crystal structure of 2-{1-[(4-fluoroanilino)methylidene]ethyl}pyridinium chloride, C(13)H(13)FN(3)(+) x Cl(-), (II), contains just one anion and one cation in the asymmetric unit but no solvent. In contrast with (I), the N-C-C-N torsion angle in the cation corresponds with a trans conformation. The cations are located parallel to the (100) plane and are connected by hydrogen bonds to the chloride anions, forming zigzag chains in the direction of the b axis. In addition, the crystal packing is stabilized by weak pi-pi interactions between the pyridinium and benzene rings. The crystal of (II) is a nonmerohedral monoclinic twin which emulates an orthorhombic diffraction pattern. Twinning occurs via a twofold rotation about the c axis and the fractional contribution of the minor twin component refined to 0.324 (3). 2-{1-[(4-Fluoroanilino)methylidene]ethyl}pyridinium chloride methanol disolvate, C(13)H(13)FN(3)(+) x Cl(-) x 2 CH(3)OH, (III), is a pseudopolymorph of (II). It crystallizes with two anions, two cations and four molecules of methanol in the asymmetric unit. Two symmetry-equivalent cations are connected by hydrogen bonds to a chloride anion and a methanol solvent molecule, forming a centrosymmetric dimer. A further methanol molecule is hydrogen bonded to each chloride anion. These aggregates are connected by C-H...O contacts to form infinite chains. It is remarkable that the geometric structures of two compounds having two different formula units in their asymmetric units are essentially the same.
authors.affiliation: Institut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Heilmann-Brohl
authors.forename: Matthias
authors.initials: M
authors.lastname: Wagner
authors.forename: Hans Wolfram
authors.initials: HW
authors.lastname: Lerner
authors.forename: Michael
authors.initials: M
authors.lastname: Bolte
mesh_terms: D018360:Crystallography, X-Ray; D006834:Hydrazines / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D015394:Molecular Structure; D011726:Pyridinium Compounds / Q000737:chemistry*
chemical_list: D006834:Hydrazines; D006846:Hydrocarbons, Halogenated; D011726:Pyridinium Compounds