Crystal structure of diethyl 3,3′-[(2-fluorophenyl)methylidene]bis(1H-indole-2-carboxylate)

In the title compound, the two indole ring systems are approximately perpendicular to one another, subtending a dihedral angle of 86.0 (5)°. In the crystal, pairs of N—H⋯O hydrogen bonds link the molecules into the inversion dimers, which are further linked by N—H⋯O hydrogen bonds into supramolecular chains propagated along the b-axis direction.

In the title compound, C 29 H 25 FN 2 O 4 , the mean planes of the two indole ring systems (r.m.s. deviations = 0.1392 and 0.0115 Å ) are approximately perpendicular to one another, subtending a dihedral angle of 86.0 (5) ; the benzene ring is twisted with respect to the mean planes of the two indole ring systems by 83.3 (2) and 88.1 (4) , respectively. In the crystal, pairs of N-HÁ Á ÁO hydrogen bonds link the molecules into centrosymmetric dimers, which are further linked by N-HÁ Á ÁO hydrogen bonds into supramolecular chains propagating along the [101] direction.

Chemical context
Bis(indolyl)methane derivatives are abundantly present in various terrestrial and marine natural resources (Poter et al., 1977;Sundberg, 1996). They are important antibiotics in the field of pharmaceuticals with diverse activities, such as anticancer, antileishmanial and antihyperlipidemic (Chang et al., 1999;Ge et al., 1999). On the other hand, bis(indoly)methane derivatives can also be used as precursors for MRI necrosis avid contrast agents (Ni, 2008). In recent years, we have reported the synthesis and crystal structures of some similar bis(indoly)methane compounds (Sun et al., 2012(Sun et al., , 2015Li et al., 2014;Lu et al., 2014). Now we report herein another bis(indoly)methane compound.

Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The two indole ring systems are nearly perpendicular to ISSN 2056-9890 each other [dihedral angle = 86.0 (5) ] while the benzene ring (C24-C29) is tilted with respect to the N1/C2-C9 and N2/C13-C20 indole ring systems, making dihedral angles of 83.3 (2) and 88.1 (4) , respectively. The carboxyl groups are approximately co-planar with the attached indole moieties, the dihedral angles between the carboxyl groups and the mean plane of the attached indole ring system being 9.5 (2) and 7.2 (3) .

Supramolecular features
In the crystal, pairs of N1-H1AÁ Á ÁO1 hydrogen bonds link the molecules into centrosymmetric dimers, which are further connected by N2-H2AÁ Á ÁO3 hydrogen bonds into supramolecular zigzag chains propagating along the [101] direction (Table 1 and Fig. 2).

Figure 2
A packing diagram of the title compound. Hydrogen bonds are shown as dashed lines.

Figure 1
The molecular structure of the title molecule with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.

Diethyl 3,3′-[(2-fluorophenyl)methylidene]bis(1H-indole-2-carboxylate)
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq F 0.1008 (3)