title: The zwitterion of 4-nitro-2-{(E)-[2-(piperidin-1-yl)ethyl]iminomethyl}phenol.
abstract: The title Schiff base compound, 4-nitro-1-oxo-2-{(E)-[2-(piperidin-1-yl)ethyl]iminiomethyl}cyclohexadienide, C(14)H(19)N(3)O(3), exists as a zwitterion, with the H atom of the phenol group being transferred to the imine N atom. The C=O, C(Ar)-C(Ar) and C-N bond lengths are in agreement with the oxocyclohexadienide-iminium zwitterionic form. The iminium H atom is engaged in a strong intramolecular hydrogen bond with the O atom of the keto group (N(+)-H...O) to form an S(6) motif. Soft C-H...O interactions in the ac plane lead to the development of hydrogen-bonded tapes, which are pi-stacked through the oxocyclohexadienide ring and iminium group. The significance of this study is in providing crystallographic evidence, supported by NMR and IR data, of the predominance of the oxocyclohexadienide-iminium zwitterion form over the noncharged canonical form in the title Schiff base.
authors.affiliation: Facultad de Ciencias Químicas, Universidad de Colima, Carretera Coquimatlán-Colima, Coquimatlán Colima, 28400, Mexico.
authors.forename: Rocio J
authors.initials: RJ
authors.lastname: Santos-Contreras
authors.forename: Angel
authors.initials: A
authors.lastname: Ramos-Organillo
authors.forename: Efrén V
authors.initials: EV
authors.lastname: García-Báez
authors.forename: Itzia I
authors.initials: II
authors.lastname: Padilla-Martínez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Martínez-Martínez
mesh_terms: D003461:Crystallography; D007097:Imines / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: C534339:4-nitro-2-((E)-(2-(piperidin-1-yl)ethyl)iminomethyl)phenol; D007097:Imines; D010636:Phenols; D010880:Piperidines