Crystal structure of a new polymorph of 3-acetyl-8-methoxy-2H-chromen-2-one

A new polymorphic form of the title compound, C12H10O4, is described in the orthorhombic space group Pbca and Z = 8, as compared to polymorph I, which crystallizes in the monoclinic space group C2/c and Z = 8 [Li et al. (2012). Chin. J. Struct. Chem. 31, 1003-1007.]. In polymorph II, the coumarin ring system is almost planar (r.m.s. deviation = 0.00129Å). In the crystal, molecules are connected by Csp ³ - H⋯O and Car - H⋯O hydrogen bonds, forming molecular sheets linked into zigzag shaped layers along the b-axis direction. The three-dimensional lattice is assembled through stacking of the zigzag layers by π-π interactions with a centroid-to-centroid distance of 3.600(9)Å and antiparallel C=O⋯C=O interactions with a distance of 3.1986(17)Å, which give rise to a helical supramolecular architecture.