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

The title compounds, (I), (II) and (III), are indole derivatives. Compounds (I) and (II) present two independent moieties in the asymmetric unit, and their packing is led by C—H⋯O hydrogen bonds and C—H⋯π interactions. In compound (III), the C—H⋯O hydrogen bonds form (22) inversion dimers.


Structural commentary
The molecular structures of title compounds (I), (II) and (III) are shown in Figs. 1, 2 and 3, respectively. Compounds (I) and (II) comprise two crystallographically independent molecules (A and B) in the asymmetric unit. The corresponding bond lengths and bond angles of molecules A and B [in compounds (I) and (II)] agree well with each other, as illustrated in Figs. 4 and 5. The indole ring systems depart slightly from planarity, the dihedral angles formed between the pyrrole rings and benzene rings being 1.65 (9) and 0.97 (10) [molecules A and B of compound (I)], 0.20 (9) and 0.86 (9) [molecules A and B of compound (II)], and 1. 34 (14) [compound (III)].
In all three compounds, as a result of the electron-withdrawing character of the phenylsulfonyl group, the N-Csp 2 bond lengths are longer than the mean value of 1.355 (14)Å for the N-C bond length (Allen et al., 1987). Atom S1 has a distorted tetrahedral configuration. The widening of the angle O1 S1 O2 and the narrowing of the angle N1-S1-C9 from ideal tetrahedral values are attributed to the Thorpe-Ingold effect (Bassindale, 1984). The widening of the angles may be due to the repulsive interaction between the two short S O bonds.

Figure 1
The molecular structure of the compound (I), showing the atomnumbering scheme. The intramolecular C2A-H2AÁ Á ÁO2A and C2B-H2BÁ Á ÁO2B interactions (molecules A and B), which generate two S(6) ring motifs, are shown as dashed lines. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The molecular structure of the compound (II), showing the atomnumbering scheme. The intramolecular C2A-H2AÁ Á ÁO2A and C2B-H2BÁ Á ÁO2B interactions (molecules A and B), which generate two S(6) ring motifs, are shown as dashed lines. Displacement ellipsoids are drawn at the 30% probability level.

Figure 3
The molecular structure of the compound (III), showing the atomnumbering scheme. The intramolecular C2-H2Á Á ÁO2 interaction, which generates an S(6) ring motif, is shown as a dashed line. Displacement ellipsoids are drawn at the 30% probability level.
In all three compounds, the expansion of the ispo angles at atoms C1, C3 and C4, and the contraction of the apical angles at atoms C2, C5 and C6 are caused by fusion of the smaller pyrrole ring with the six-membered benzene ring and the strain is taken up by the angular distortion rather than by bond-length distortion (Allen, 1981).
The sums of the bond angles around atoms N1 are 351.55 and 356.16 in (I), 359.86 and 359.29 in (II), and 352.79 in (III), indicating sp 2 hybridization. In all three compounds, the molecular structure is stabilized by intramolecular C-HÁ Á ÁO hydrogen bonds which generate S(6) ring motifs with the sulfone O atom (Tables 1, 2 and 3). In addition to these, in compound (III), the molecular structure is characterized by intramolecular C25-Cl3Á Á ÁO2 halogen bonding (XB), between the solvent Cl atom (Cl3) and sulfone-group O atom (O2) [Cl3Á Á ÁO2 = 3.036 (2) Å and with a bond angle of 164.48 (14) ].

Supramolecular features
In the crystal packing of compound (I), the molecules are linked via intermolecular C16B-H16BÁ Á ÁO2A(Àx + 1, y +  Molecules A (red) and molecule B (black) of title compound (I) overlapping with each other. H atoms are shown as spheres of arbitrary radius.

Figure 5
The molecule A (red) and molecule B (black) of title compound (II) overlapping with each other. H atoms are shown as spheres of arbitrary radius. Table 1 Hydrogen-bond geometry (Å , ) for (I).

Figure 7
The crystal packing of compound (II), viewed down the b axis, showing C12B-H12BÁ Á ÁO2A i intermolecular hydrogen bond running parallel to the [101] direction and further intercomnnected by C5A-H5AÁ Á ÁCg1 ii and C17B-H17CÁ Á ÁCg2 ii interactions. H atoms not involved in the hydrogen bonding have been omitted for clarity. Cg1 and Cg2 are the centres of the gravity of benzene rings C9A-C14A and C1A-C6A, respectively. [Symmetry codes: (i) x + 1, y, z À 1; (ii) Àx + 1, Ày + 1, Àz + 1.] toluene (20 ml) was refluxed for 12 h under an N 2 atmosphere. After consumption of the starting material [monitered by thinlayer chromatography (TLC)], removal of the solvent in vacuo followed by column chromatographic purification (silica gel, EtOAc-hexane 1:9 v/v) gave (I) (yield 1.30 g, 29%) as a colourless solid. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of compound (I) in ethyl acetate at room temperature (m.p. 383-385 K).

Compound (II)
Reaction of 2-bromomethyl-1-(1-phenylsulfonyl-1H-indol-3-yl)ethan-1-one (0.2 g, 5 mmol) with K 2 CO 3 (0.35 g, 5 mmol) in acetonitrile was carried out under reflux for 8 h under an N 2 atmosphere. After the consumption of the starting material (monitered by TLC), the reaction mass was poured over crushed ice and extracted with dichloromethane (2 Â 15 ml). The organic layers were combined and washed with brine solution (2 Â 20 ml) and dried (Na 2 SO 4 ). The crude product was purified by column chromatography (silica gel, EtOAchexane 1:4 v/v) to give (II) (yield 1.40 g, 88%) as a white solid. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of compound (II) in ethyl acetate at room temperature (m.p. 475-481 K).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.