10-Ethyl-3-(5-methyl-1,3,4-oxadiazol-2-yl)-10H-phenothiazine

In the title compound, C17H15N3OS, the phenothiazine ring system is slightly bent, with a dihedral angle of 13.68 (7)° between the benzene rings. The dihedral angle between the oxadiazole ring and the adjacent benzene ring is 7.72 (7)°. In the crystal, a π–π interaction with a centroid–centroid distance of 3.752 (2) Å is observed between the benzene rings of neighbouring molecules.

In the title compound, C 17 H 15 N 3 OS, the phenothiazine ring system is slightly bent, with a dihedral angle of 13.68 (7) between the benzene rings. The dihedral angle between the oxadiazole ring and the adjacent benzene ring is 7.72 (7) . In the crystal, ainteraction with a centroid-centroid distance of 3.752 (2) Å is observed between the benzene rings of neighbouring molecules.

Comment
The derivatives of phenothiazine are a series important chemical intermediates in design of the dye-sensitized solar cells (DSSCs) (Kim et al., 2011;Hagfeldt et al., 2010). As part of our interest in these materials, here we report the crystal structure of the title compound C 17 H 15 N 3 OS.
The title molecule is in a nonlplanar butterfly conformation with a dihedral angle of 13.68 (7)° between two benzene rings ( Fig. 1). The crystal packing exhibits a π-π interaction with a centroid-centroid distance of 3.752 (2) Å between the benzene rings from the neighbouring molecules.

Experimental
A solution of 5-[3-(10-ethyl)phenothiazyl]-tetrazole (500 mg, 1.69 mmol) in 10 ml acetic anhydride was heated to reflux and stirred for 1 h. The excess acetic anhydride was evaporated and the residue solid was extracted three times with dichloromethane. Then the organic layer was washed with water and dried with anhydrous sodium sulfate. After removal of the solvent, the crude product was purified by chromatography on a silica gel column using dichloromethane-ethyl acetate (v/v = 10:1) as eluent and isolated as a yellow powder. Yield: 472 mg (90%). The yellow single crystals suitable for X-ray diffraction were obtained after several days by slow evaporation of a mixture solution of dichloromethane and petroleum ether.

Refinement
H atoms were placed in calculated positions (C-H = 0.93-0.97 Å) and treated as riding atoms, with U iso (H) = 1.2 or 1.5U eq (C).