Diethyl 3,3′-[(3-fluorophenyl)methylene]bis(1H-indole-2-carboxylate)

In the title compound, the indole ring systems are approximately perpendicular to one another with a dihedral angle of 88.3 (4)°.

In the title compound, C 29 H 25 FN 2 O 4 , the mean planes of the indole ring systems are approximately perpendicular to one another [dihedral angle = 88.3 (4) ]. The benzene ring is twisted with respect to the indole ring systems by 49.8 (5) and 77.6 (3) . In the crystal, pairs of N-HÁ Á ÁO hydrogen bonds link the molecules into the inversion dimers which are further linked into supramolecular chains propagating along the [110] direction.

Structure description
There are abundant bis(indolyl)methane derivatives in various terrestrial and marine natural resources (Sundberg, 1996). As part of our ongoing studies of bis(indoyl)methane compounds, we now report the synthesis and crystal structure of the title compound.
The molecular structure of the title compound is shown in Fig. 1. The indole ring systems are nearly perpendicular to one another [dihedral angle = 88.3 (4) ] while the benzene ring (C2-C7) is twisted with respect to the N1/C8-C15 and N2/C19-C26 indole ring systems with dihedral angles of 49.8 (5) and 77.6 (3) , respectively. The carboxyl groups are approximately co-planar with their attached indole ring systems, the dihedral angles between the carboxyl groups and the mean planes of the N1/C8-C15 and N2/C19-C26 indole ring systems being 6.2 (5) and 6.4 (4) , respectively.

Synthesis and crystallization
Ethyl indole-2-carboxylate (1.88 g, 10 mmol) was dissolved in 20 ml of ethanol and 3-fluorobenzaldehyde (0.62 g, 5 mmol) and concentrated HCl (0.5 ml) was added. The mixture was heated to reflux temperature for 2 h. After cooling, the white product was filtered off and washed thoroughly with ethanol (yield = 92%). Single crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution.

Figure 1
The molecular structure of the title molecule with displacement ellipsoids drawn at the 30% probability level.

data-1
IUCrData ( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.009 Δρ max = 0.56 e Å −3 Δρ min = −0.71 e Å −3 data-2 IUCrData (2020). 5, x200912 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. H atoms were positioned geometrically with N-H = 0.86 Å and C-H = 0.93-0.98 Å, and constrained to ride on their parent atoms. The constraint U iso (H) = 1.2U eq (C,N) or 1.5U eq (methyl C) was applied in all cases.