title: 1-(7-chloro-1,4-dihydroquinolin-4-ylidene)thiosemicarbazide and its hydrochloride: evidence for the existence of a stable imine tautomer in the solid state of 4-aminoquinoline free bases, an anomalous case in nitrogen heterocycles.
abstract: In the solid state, crystals of both 1-(7-chloro-1,4-dihydroquinolin-4-ylidene)thiosemicarbazide-methanol-water (2/1/1), 2C10H9ClN4S·CH3OH·H2O, (I), and its hydrochloride salt {systematic name: [(7-chloro-1,4-dihydroquinolin-4-ylidene)azaniumyl]thiourea chloride}, C10H10ClN4S(+)·Cl(-), (II), assume the imine tautomeric form, contrary to other 4-amino-7-chloroquinolines. Of particular interest are the N-C bond lengths, which have appreciable double-bond character, and the C-N-C aromatic ring bond angle. Both of these parameters have been studied extensively in 4-amino-substituted quinolines. The crystal structures of (I) and (II) in this study provide interesting examples of the amino-imino tautomerism which exists in this class of compound and is, to the best of our knowledge, hitherto unreported.
authors.affiliation: Department of Chemistry, Federal University of Juiz de Fora, Minas Gerais 36036-900, Brazil.
authors.forename: Rafael C
authors.initials: RC
authors.lastname: Machado
authors.affiliation: Department of Chemistry, Federal University of Juiz de Fora, Minas Gerais 36036-900, Brazil.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Grazul
authors.affiliation: Grupo de Cristalografia de Pequenas Moléculas (GCPMOL), Department of Chemistry, Federal University of Juiz de Fora, Minas Gerais 36036-900, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Diniz
mesh_terms: D000634:Aminoquinolines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*; D012663:Semicarbazides / Q000737:chemistry*; D013882:Thiosemicarbazones / Q000737:chemistry*
chemical_list: C000602398:1-(7-chloro-1,4-dihydroquinolin-4-ylidene)thiosemicarbazide; D000634:Aminoquinolines; D006571:Heterocyclic Compounds; D011804:Quinolines; D012663:Semicarbazides; D013882:Thiosemicarbazones; C005151:thiosemicarbazide; C001920:4-aminoquinoline; D009584:Nitrogen
keywords: 4-aminoquinoline; Hirshfeld surface analysis; alpha effect; amino–imino tautomerism; crystal structure; solid-state structure; thiosemicarbazide