Crystal structure of a new polymorph of 3-acetyl-8-meth-oxy-2H-chromen-2-one.

A new polymorphic form of the title compound, C(12)H(10)O(4), is described in the ortho-rhom-bic 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 = 0.00129†à ). In the crystal, mol-ecules are connected by Csp (3)-H⋯O and C(ar)-H⋯O hydrogen bonds, forming mol-ecular 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 inter-actions with a centroid-to-centroid distance of 3.600†(9)†à and anti-parallel C=O⋯C=O inter-actions with a distance of 3.1986†(17)†à , which give rise to a helical supra-molecular architecture.