Crystal structures of three indole derivatives: 3-ethnyl-2-methyl-1-phenylsulfonyl-1 H -indole, 4-phenylsulfonyl-3 H ,4 H -cyclopenta[ b ]indol-1(2 H )-one and 1-{2-[( E )-2-(5-chloro-2-nitrophenyl)ethenyl]-1-phenylsulfonyl-1 H -indol-3-yl}ethan-1-one chloroform monosolvate

The title compounds, C 17 H 13 NO 2 S, (I), C 17 H 13 NO 3 S, (II), and C 24 H 17 ClN 2 O 5 S·CHCl 3 , (III), are indole derivatives. Compounds (I) and (II) crystalize with two independent molecules in the asymmetric unit. The indole ring systems in all three structures deviate only slightly from planarity, with dihedral angles between the planes of the pyrrole and benzene rings spanning the tight range 0.20 (9)–1.65 (9)°. These indole ring systems, in turn, are almost orthogonal to the phenylsulfonyl rings [range of dihedral angles between mean planes = 77.21 (8)–89.26 (8)°]. In the three compounds, the molecular structure is stabilized by intramolecular C—H...O hydrogen bonds, generating S (6) ring motifs with the sulfone O atom. In compounds (I) and (II), the two independent molecules are linked by C—H...O hydrogen bonds and C—H...π interactions, while in compound (III), the molecules are linked by C—H...O hydrogen bonds, generating R 2 2 (22) inversion dimers.