Crystal structures of two new carbazole derivatives: 12-(4-nitro-phen-yl)-7-phenyl-sulfonyl-7 H -benzofuro[2,3- b ]carbazole and 2-methyl-4-(4-nitro-phen-yl)-9-phenyl-sulfonyl-9 H -thieno[2,3- b ]carbazole.

The title compounds, C ₃₀ H ₁₈ N ₂ O ₅ S, (I), and C ₂₇ H ₁₈ N ₂ O ₄ S ₂ , (II), are carbazole derivatives with a phenyl-sulfonyl group and a nitro-phenyl group attached to the carbazole moiety in identical positions in both mol-ecules. A benzo-furan ring system in (I) and a methyl-thio-phene ring in (II) are fused with the respective carbazole moieties on the same sides. The mean plane of the carbazole ring system makes a dihedral angle of 3.17 (7)° with the benzo-furan ring system in (I) and a dihedral angle of 3.39 (11)° with the methyl-thio-phene ring in (II), implying that both fused units are essentially planar. The mean planes of the carbazole ring systems in both the compounds are almost orthogonal to the respective nitro-substituted phenyl rings, making dihedral angles of 75.64 (10) and 77.63 (12)° in compounds (I) and (II), respectively. In (I), the phenyl-sulfonyl ring system is positionally disordered with a refined occupancy ratio of 0.63 (2):0.37 (2). In both compounds, the mol-ecular structures are stabilized by intra-molecular C-H⋯O hydrogen bonds, generating S (6) ring motifs with the sulfone group O atoms. In the crystal of compound (I), mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, which generate R ₂ ² (18) inversion dimers, and inter-connected by C (14) chains running along the c -axis direction, whereas in compound (II), the C-H⋯O hydrogen bonds generate R ₄ ³ (37) ring motifs. In the crystals of both compounds, C-H⋯O hydrogen-bonded sheets are formed lying parallel to (10-1). In addition, C-H⋯π and offset π-π inter-actions [inter-centroid distance = 3.7158 (14) Å in (I) and 3.9040 (15) Å in (II)] are also present in the crystals of both compounds.