Crystal structure of 5-[2-(9H-carbazol-9-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione

Abstract

The title compound, C 16 H 13 N 3 OS, comprises an oxadiazolethione ring bound to the N atom of an almost planar carbazole ring system (r.m.s. deviation = 0.0088 Å ) through an ethylene chain. The oxadiazole ring is inclined to the the carbazole ring system by 40.71 (6) . In the crystal, N-HÁ Á ÁO, N-HÁ Á ÁS, C-HÁ Á ÁN and C-HÁ Á ÁS hydrogen bonds combine with C-HÁ Á Á (ring) andcontacts to stack the molecules along the b-axis direction. Chemical contextCarbazole derivatives have been shown to have several industrial applications including use in optoelectronic devices (Fitilis et al., 2007;Peng et al., 2011), dye-sensitized solar cells (Li et al., 2010) and photochromic dyes (Billah et al., 2008). Moreover, fused heterocycles with carbazole scaffolds are noted for their biological activities. They are found in drugs such as tubingensin A and B and have been shown to have both antiviral and cytotoxic activities (TePaske et al., 1989). The anti-inflammatory agents caprofen and etodolaca and the antipyretic agent nincazole (Ghoneim et al., 2006) are also carbazole based. The biological activity of so many carbazolebased heterocycles encouraged us to synthesize the title compound and its molecular crystal structure is reported here. Structural commentaryIn the title compound C 16 H 13 N 3 OS, (I), the oxadiazolethione ring binds to the carbazole ring system through a C2-C3-C4-N3 ethylene chain with the ring systems inclined at an angle of ISSN 2056-9890 40.71 (6) , Fig. 1. The carbazole ring system is almost planar with the outer C5-C10 and C11-C16 benzene rings subtending angles of 0.38 (13) and 0.64 (13) , respectively, to the central N3/C5/C10/C11/C16 ring. Bond lengths and angles in both ring systems are normal and similar to those found in the numerous other carbazole structures (see, for example, Kimura et al., 1985) and those of the few known oxadiazolethione derivatives with alkane chains at C5 (Khan et al. 2014;Zheng et al. 2006). Supramolecular featuresIn the crystal, classical N1-H1NÁ Á ÁO1 and N1-H1NÁ Á ÁS1 hydrogen bonds form C(4) chains of molecules linked in a head-to-head fashion along the b-axis direction, Fig. 2. These contacts are bolstered by the C4 atom acting as a bifurcated donor forming weaker C4-H4AÁ Á ÁN2 hydrogen bonds and C4-H4BÁ Á ÁCg4 interactions, Table 1. In the chains, the mean plane of the oxadiazole ring is inclined at 10.7 to (101). The N-HÁ Á ÁO and N-HÁ Á ÁS hydrogen bonds also impose close O1Á Á ÁN2(x, y À 1, z) contacts of 2.9516 (18) Å . Adjacent chains are further linked by C3-H3BÁ Á ÁS1 hydrogen bonds that form inversion dimers, enclosing R 2 2 (12) rings. This combination of contacts stacks molecules along the b-axis direction, Fig. 3. Adjacent oxadiazole rings form dimers through Cg1Á Á ÁCg1 vi -contacts with centroid-to-centroid separations of 3.3931 (9) Å Cg1 is the centroid of the O1/C2/ N3/N4/C5 ring; symmetry code: (vi) 1 À x, 1 À y, 1 À z]. These dimers are linked by much weaker C12-H12Á Á ÁCg4 interactions, Table 1 The molecular structure of (I) with ellipsoi...