2-[2-(5-nitro-2-thienyl)ethenyl]-4H-3,1-benzoxazine-4-one, 2-[2-(4-nitro-phenyl)ethenyl]-4H-3,1-benzoxazine-4-one and 6,7-dimethoxy-2-[2-(4-nitrophenyl)ethenyl]-4H-3,1-benz-oxazine-4-one

The three title compounds, i.e. C14H8N2O4S, (I), C16H10N2O4, (II), and C18H14N2O6, (III), respectively, are almost planar. The benzoxazinone and nitroaryl moieties are in a trans configuration with respect to the ethylene group. The nitro group in all three molecules is almost coplanar with the aryl substituent and shows quite strong conjugation with the rest of the pi-system of the molecules. The molecules of (I) form layers along the crystallographic b axis, with a distance between adjacent layers of about 3.5 Angstrom. However, the molecules of (II) and (III) form stacks, with distances between adjacent molecules of about 6.0 and 3.6 Angstrom, respectively. [GRAPHICS]