title: Crystal structure of 8-hy-droxy-quinoline: a new monoclinic polymorph.
abstract: In an attempt to grow 8-hy-droxy-quinoline-acetamino-phen co-crystals from equimolar amounts of conformers in a chloro-form-ethanol solvent mixture at room temperature, the title compound, C9H7NO, was obtained. The mol-ecule is planar, with the hy-droxy H atom forming an intra-molecular O-H⋯N hydrogen bond. In the crystal, mol-ecules form centrosymmetric dimers via two O-H⋯N hydrogen bonds. Thus, the hy-droxy H atoms are involved in bifurcated O-H⋯N hydrogen bonds, leading to the formation of a central planar four-membered N2H2 ring. The dimers are bound by inter-molecular π-π stacking [the shortest C⋯C distance is 3.2997 (17) Å] and C-H⋯π inter-actions into a three-dimensional framework. The crystal grown represents a new monoclinic polymorph in the space group P21/n. The mol-ecular structure of the present monoclinic polymorph is very similar to that of the ortho-rhom-bic polymorph (space group Fdd2) studied previously [Roychowdhury et al. (1978 ▶). Acta Cryst. B34, 1047-1048; Banerjee & Saha (1986 ▶). Acta Cryst. C42, 1408-1411]. The structures of the two polymorphs are distinguished by the different geometries of the hydrogen-bonded dimers, which in the crystal of the ortho-rhom-bic polymorph possess twofold axis symmetry, with the central N2H2 ring adopting a butterfly conformation.
authors.affiliation: Department of Chemistry & Biology, New Mexico Highlands University, 803 University Avenue, Las Vegas, NM 87701, USA.
authors.forename: Raúl
authors.initials: R
authors.lastname: Castañeda
authors.affiliation: Department of Chemistry & Biology, New Mexico Highlands University, 803 University Avenue, Las Vegas, NM 87701, USA.
authors.forename: Sofia A
authors.initials: SA
authors.lastname: Antal
authors.affiliation: Department of Chemistry & Biology, New Mexico Highlands University, 803 University Avenue, Las Vegas, NM 87701, USA.
authors.forename: Sergiu
authors.initials: S
authors.lastname: Draguta
authors.affiliation: Department of Chemistry & Biology, New Mexico Highlands University, 803 University Avenue, Las Vegas, NM 87701, USA.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Timofeeva
authors.affiliation: X-Ray Structural Centre, A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilov Street, B-334, Moscow 119991, Russian Federation.
authors.forename: Victor N
authors.initials: VN
authors.lastname: Khrustalev
keywords: 8-hy­droxy­quinoline; crystal structure; hydrogen bonds; polymorphism