Crystal structure of (Z)-2-(1-benzyl-2-oxoindolin-3-ylidene)-N-phenylhydrazine-1-carbothioamide

The title compound, C22H18N4OS, crystallized with four independent molecules (A, B, C and D) in the asymmetric unit. All four molecules have a Z conformation about the C=N bond with the benzyl ring being inclined to the indoline ring mean planes by 73.4 (2), 77.9 (2), 73.2 (2) and 77.2 (2)° in molecules A, B, C and D, respectively. In molecules A and B, the phenyl ring is inclined to the mean plane of the indoline ring mean plane by 12.0 (2) and 12.2 (2)°, respectively. However, in molecules C and D, the same dihedral angles are larger, viz. 37.3 (2) and 36.4 (2)°, respectively. Consequently, the benzyl and phenyl rings are almost normal to one another in molecules A and B [dihedral angles = 80.3 (3) and 87.1 (3)°, respectively], while in molecules C and D, the same dihedral angles are only 48.8 (2) and 43.8 (3)°, respectively. There is an intramolecular N—H⋯O hydrogen bond in each molecule with an S(6) ring motif. There are also short intramolecular N—H⋯N and C—H⋯S contacts in each molecule. In the crystal, molecules are linked via C—H⋯S hydrogen bonds and C—H⋯π interactions, forming a three-dimensional structure. The crystal was refined as a non-merohedral twin with a final BASF value of 0.110 (1).


S3. Comment
The design and synthesis of thiosemicarbazones are of considerable interest because of their versatile chemistry and various biological activities such as antitumor, antibacterial, antiviral, antiamoebic and antimalarial (Kelly et al., 1996).
They comprise an intriguing class of chelating molecules which possess a wide range of beneficial medicinal properties (Prabhakaran et al., 2008). Thiosemicarbazones are a versatile class of ligands that have been studied for their biological activity (Chellan et al., 2010), their interesting binding motifs (Lobana et al., 2009) and they use as ligands in catalysis (Xie et al., 2010). In view of this biological importance, the crystal structure of the title compound has been determined and the results are presented herein.
The molecular structures of the four independent molecules (A_S1, B_S2, C_S3, D_S4) of the title compound are illustrated in Fig. 1. All four molecules have a Z conformation about the C═N bond with the benzyl ring being inclined to the indoline ring mean plane by 73.4 (2), 77.9 (2), 73.2 (2) and 77.2 (2) ° in molecules A, B, C and D, respectively. In molecules A and B the phenyl ring is inclined to the mean plane of the indoline ring mean plane by 12.0 (2) and 12.2 (2) °, respectively. However, in molecules C and D the same dihedral angles are larger; 37.3 (2) and 36.4 (2) °, respectively.
Consequently, the benzyl and phenyl rings are almost normal to one another in molecules A and B (dihedral angles of 80.3 (3) and 87.1 (3) °, respectively), while in molecules C and D the same dihedral angles are only 48.8 (2) and 43.8 (3) °, respectively. There is an intramolecular N-H···O hydrogen bond in each molecule with an S(6) ring motif (Table 1).
In the crystal, molecules are linked via C-H···S hydrogen bonds and C-H···π interactions forming a three-dimensional structure (Table 1 and Fig. 2).

Figure 1
The molecular structure of the four independent molecules (atom S1 is in molecule A, S2 is in B, S3 in C and S4 in D) of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 10% probability level.

Figure 2
A view along the a axis of the crystal packing of the title compound showing the hydrogen bonds as dashed lines (see Table 1 for details; molecule colour code: A black, B red, C green, D blue). Hydrogen atoms not involved in hydrogen bonding have been omitted for clarity.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1 0.4308 (