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 ß and ß' 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.