4-(Diphenylamino)benzaldehyde 4-phenylthiosemicarbazone

The title molecule, C26H22N4S, is composed of three main parts, viz. a triphenylamine group is connected to a phenyl ring by a thiosemicarbazone moiety. The C= N double bond has an E conformation. The crystal packing is dominated by strong hydrogen bonds through the thiosemicarbazone moiety, with pairs of N—H⋯S hydrogen bonds linking the molecules to form inversion dimers with an R 2 2(8) ring motif. An intramolecular N—H⋯N hydrogen bond is also present, generating an S(5) ring motif. Although the structure contains four phenyl rings, π–π stacking interactions are not formed between them, probably due to the conformation adopted by the triphenylamine group. However, a weak π–π stacking interaction is observed between the phenyl ring and the delocalized thiosemicarbazone moiety.

The title molecule, C 26 H 22 N 4 S, is composed of three main parts, viz. a triphenylamine group is connected to a phenyl ring by a thiosemicarbazone moiety. The C N double bond has an E conformation. The crystal packing is dominated by strong hydrogen bonds through the thiosemicarbazone moiety, with pairs of N-HÁ Á ÁS hydrogen bonds linking the molecules to form inversion dimers with an R 2 2 (8) ring motif. An intramolecular N-HÁ Á ÁN hydrogen bond is also present, generating an S(5) ring motif. Although the structure contains four phenyl rings,stacking interactions are not formed between them, probably due to the conformation adopted by the triphenylamine group. However, a weakstacking interaction is observed between the phenyl ring and the delocalized thiosemicarbazone moiety.
Financial support of this work was given by the Agencia Españ ola de Cooperació n Internacional y Desarrollo (AECID). The authors also acknowledge FEDER funding and funds from the Spanish MINECO (grant Nos. MAT2006-01997, MAT2010-15094) and Factoría de Cristalizació n Consolider Ingenio-2010. Taking into account geometrical values calculated with Platon program is not feasible the existence π-π interactions involved triaphenylamine group. However, we observed a weak π-π stacking interaction between phenyl ring (R4) and the thiosemicarbazone deslocalized system (C═N-NH-C═S-NH) with distance to N3 (3.834 (3) Å) and dihedral angle (4.68 (2)°) shown in Fig. 4.

Experimental
A solution of 4-(diphenylamino)benzaldehyde (2.7333 g, 0.01 mol) and 4-phenylthiosemicarbazide (1.6723 g, 0.01 mol) in absolute ethanol (70 ml) was refluxed for 4 h in the presence of p-toluenesulfonic acid as catalyst, with continuous stirring. On cooling to room temperature the precipitate was filtered off, washed with copious cold ethanol and dried in air. Yellow single crystals of compound (I) were obtained after recrystallization from a solution in ethanol after 2 d.

Figure 1
A view of the molecular structure of the title molecule. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The three main parts of the molecular structure, divided into apolar groups (R1, R2, R3, R4) and H-bonding domain.    Representation of the weak π-π stacking interaction between phenyl ring (R4) and the thiosemicarbazone deslocalized system.

Special details
Experimental. Absorption correction: CrysAlisPro, Oxford Diffraction Ltd., Version 1.171.34.36 (release 02-08-2010 CrysAlis171 .NET) (compiled Aug 2 2010,13:00:58) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. 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.