Polymorphism of coumarin thione-triazole - 4-methyl-7-[(4-phenyl-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methoxy]-2H-chromen-2-one

Abstract

Two novel polymorphs (Form I and II) of coumarin thione-triazole - 4-methyl-7-[(4-phenyl-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methoxy]-2H-chromen-2-one, have been prepared by recrystallization of the crude product from water (Form I) and acetonitrile (Form II). Crystal structures of both forms were determined by the single-crystal X-ray diffraction and additionally characterized by FT-IR spectroscopy and thermal analysis. Single-crystal X-ray diffraction experiments revealed that two polymorphs crystalize in different crystal systems (orthorhombic and monoclinic), with different hydrogen bonding schemes and packing arrangements. In Form I, molecules are primarily connected via NH⋯O hydrogen bonds. Molecules of Form II are primarily connected by offset π···π interactions in the crystal structure. The intermolecular interactions in both crystal structures were further studied by the Hirshfeld surface analysis and intermolecular energy utilizing theoretical calculation. The DSC analysis revealed that Form II is a higher melting point form. Further analysis indicates the monotropic relationship between polymorphs. The Cambridge Structural Database search showed that this is the first structurally characterized compound containing coumarin thione-triazole moieties.