Two polymorphs of N‐(2‐methoxyphenyl)‐4‐oxo‐4H‐chromone‐3‐carboxamide. (28th August 2013) - Gomes, Ligia R.
Abstract : The title compound, C17 H13 NO4, crystallizes in two polymorphic forms, each with two molecules in the asymmetric unit and in the monoclinic space group P 21 / 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.