title: Two polymorphs of N-(2-methoxyphenyl)-4-oxo-4H-chromone-3-carboxamide.
abstract: The title compound, C₁₇H₁₃NO₄, crystallizes in two polymorphic forms, each with two molecules in the asymmetric unit and in the monoclinic space group P2₁/c. All of the molecules have intramolecular hydrogen bonds involving the amide group. The amide N atoms act as donors to the carbonyl group of the pyrone and also to the methoxy group of the benzene ring. The carbonyl O atom of the amide group acts as an acceptor of the β and β' C atoms belonging to the aromatic rings. These intramolecular hydrogen bonds have a profound effect on the molecular conformation. In one polymorph, the molecules in the asymmetric unit are linked to form dimers by weak C-H∙∙∙O interactions. In the other, the molecules in the asymmetric unit are linked by a single weak C-H∙∙∙O hydrogen bond. Two of these units are linked to form centrosymmetric tetramers by a second weak C-H∙∙∙O interaction. Further interactions of this type link the molecules into chains, so forming a three-dimensional network. These interactions in both polymorphs are supplemented by π-π interactions between the chromone rings and between the chromone and methoxyphenyl rings.
authors.affiliation: REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal.
authors.forename: Ligia R
authors.initials: LR
authors.lastname: Gomes
authors.forename: John Nicolson
authors.initials: JN
authors.lastname: Low
authors.forename: Fernanda
authors.initials: F
authors.lastname: Borges
authors.forename: Fernando
authors.initials: F
authors.lastname: Cagide
mesh_terms: D002867:Chromones / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D002867:Chromones
keywords: crystal structure; molecular conformation; pharmaceutical compounds; polymorphs