Crystal structure of 5-[bis(4-ethoxyphenyl)amino]thiophene-2-carbaldehyde

In the title compound, C21H21NO3S, the planes of the two benzene rings are nearly perpendicular to one another [dihedral angle = 84.50 (10)°] and they are oriented with respect to the plane of the thiophene ring at dihedral angles of 59.15 (9) and 66.61 (9)°. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, forming supramolecular chains propagating along the b-axis direction.

It possesses typical propeller structure, just the same with other triarylamine. The carbonyl group is coplanar with the thiophene ring, which indicates well conjugation. As shown in Fig.2, for the existence of intermolecular C2-H2A···O3 hydrogen bond, the one-dimensional linear chain structure was formed along b axis.

S2. Experimental
The intermediate bis(4-ethoxyphenyl)amine was synthesized according to following procedure. Cuprous iodide (0.95 g, 5 mmol), L-Proline (1.15 g, 10 mmol) and anhydrous potassium carbonate (13.8 g, 100 mmol) were placed in an ovendried 250 ml Schlenk flask. The reaction vessel was evacuated and filled with prepurified argon, a process which was repeated three times. Then refined dimethylsulfoxide (100 ml) was added with a syringe under a counterflow of argon.
After that, 4-Iodophenetole (12.5 g, 50 mmol), Phenetidine (8.23 g, 60 mmol) and a particle of 18-Crown-6 (0.1981 g, 0.75 mmol) were added. The reaction was stirred at 90 degrees celsius for 24 h. Upon completion of the reaction, the mixture was cooled to room temperature. The mixture was filtered through a Buchner funnel to remove the deposition.
Then diluted with water (500 ml) and stirred for one day. A kind of grey educt were obtained after separate the water by a Buchner funnel again. Purification of the residue by column chromatography on silica gel (petroleum ether/ethyl acetate The synthesis of the title compound. Phenanthroline (0.45 g, 2.3 mmol), cuprous iodide (0.46 g, 2.4 mmol), anhydrous potassium carbonate (5.00 g, 36 mmol) and bis(4-ethoxyphenyl)amine (3.09 g, 12 mmol) were placed in an oven-dried 250 ml Schlenk flask. The reaction vessel was evacuated and filled with prepurified argon, a process which was repeated three times. Then refined dimethylsulfoxide (120 ml) and 1.90 g 5-Bromo-2-thiophenecarbalde-hyde (10 mmol) were added with a syringe under a counterflow of argon. At last, a particle of 18-Crown-6 (0.0396 g, 0.15 mmol) and two drops of Aliquat336 (0.0200 g, 0.05 mmol) were added. The reaction was stirred at 90 degrees celsius for 48 h. Upon completion of the reaction, the mixture was cooled to room temperature. The mixture was filtered through a Buchner funnel to remove the deposition. Then diluted with water (500 ml) and stirred for one day. A kind of yellowish-brown educt were obtained after separate the water by a Buchner funnel again. Purification of the residue by column chromatography on silica gel (Petroleum/Ethyl Acetate = 20:1) gave title compound as yellowish-brown particle, with

S3. Refinement
All hydrogen atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C -H = 0.93-0.97 Å, U iso (H) = 1.2 U eq (C) or 1.5U eq (C).

Figure 1
The molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H The infinite one-dimensional linear chain structure.

5-[Bis(4-Ethoxyphenyl)amino]thiophene-2-carbaldehyde
Crystal data 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.