10-(Prop-2-yn-1-y1)-2,7-diazaphenothiazine

In the title molecule [systematic name: 10-(prop-2-yn-l-y1)dipyrido[3,4-b:31,41-e][1,4]thiazine], C13H9N3S, the dihedral angle between the two pyridine rings is 146.33 (7) and the angle between two halves of the thiazine ring is 138.84 (8), resulting in a butterfly shape for the tricyclic system. The central thiazine ring adopts a boat conformation, with the 2propynyl substituent at the thiazine N atom located in a pseudo-equatorial position and oriented to the concave side of the diazaphenothiazine system. In the crystal, molecules are arranged via pi-pi interactions between the pyridine rings [centroid-centroid distances = 3.838 (1) and 3.845 (1) A] into stacks extending along [001]. There are C-H center dot center dot center dot C and CH center dot center dot center dot N interactions between molecules of neighbouring stacks.