Benzo[a][1,4]benzothia-zino[3,2-c]phenothia-zine

The title compound, C₂₂H₁₂N₂S₂, crystallizes in space group P2₁/c with four mol-ecules in the asymmetric unit. The heterocyclic mol-ecule is quasi-planar with a dihedral angle between the phenyl rings on the periphery of the mol-ecule of 1.73 (19)°. Short H⋯S (2.92 Å) and C-H⋯π [2.836 (3) Å] contacts are observed in the crystal with shorted π-π stacking distances of 3.438 (3) Å along the b axis. Surprisingly, and unlike a closely related material, this mol-ecule readily forms large crystals by sublimation and by slow evaporation from di-chloro-methane. The maximum absorbance in the UV-Vis spectrum is at 533 nm. Emission was measured upon excitation at 533 nm with a fluorescence λ_max of 658 nm and cutoff of 900 nm.