X-ray diffraction study of crystals of the organic luminophore Orlyum White 520T

The crystal and molecular structures of two crystal forms (pale yellow form 1 and yellow form 2) of N-[2-(4-oxo-4H-benzo[d][1,3]oxazin-2-yl)phenyl]naphthalene-2-sulfonamide (Orlyum White 520T), which is an organic luminophore with an anomalously high Stokes shift, were determined. Crystal 2 is a solvate with para-xylene. Crystal 1 is a solvent-free form. The molecular geometry in crystal 1 differs from that in 2 only in the orientation of the SO2Ar substituent. The bond-length distribution in the planar moiety of the molecule in crystal 1 is virtually identical to that in 2, but the bonds in the NH-SO2Ar-bearing benzene ring in crystal 1 are systematically longer than the corresponding bonds in crystal 2. This fact can be attributed to the crystal-packing effects. In 2 the molecules form stacked dimers with π-stacking interactions between two planar conjugated tricyclic systems. The charge transfer in this system accounts for the intensification of the color of these crystals and the observed difference in the optical properties of 1 and 2.