1,1′-Diphenyl-3,3′-(p-phenylenedicarbonyl)dithiourea

The molecule of the title compound, C22H18N4O2S2, lies across a crystallographic inversion centre. The central benzene ring forms dihedral angles of 29.39 (9) and 79.11 (12)°, respectively, with the thiourea unit and the terminal phenyl ring. Intramolecular N—H⋯O hydrogen bonds generate two S(6) ring motifs. In the crystal, molecules are linked into chains along [10] by intermolecular N—H⋯S hydrogen bonds.

The molecule of the title compound, C 22 H 18 N 4 O 2 S 2 , lies across a crystallographic inversion centre. The central benzene ring forms dihedral angles of 29.39 (9) and 79.11 (12) , respectively, with the thiourea unit and the terminal phenyl ring. Intramolecular N-HÁ Á ÁO hydrogen bonds generate two S(6) ring motifs. In the crystal, molecules are linked into chains along [110] by intermolecular N-HÁ Á ÁS hydrogen bonds.

Comment
The asymmetric unit of the title compound contains one-half of the molecule the other half being generated by the crystallographic inversion centre (Fig. 1). The thiourea fragment (S1/O1/N1/N2/C6/C7/C8) is planar, with atom C8 has the maximum deviation of 0.038 (2)Å from the mean plane. The dihedral angle between the central bridging benzene ring and the thiourea unit is 29.39 (9)° and that between the two benzene rings is 79.11 (12)°. The carbonyl and N-H groups are involved in intramolecular N-H···O hydrogen bonding resulting in the formation of two six-membered rings viz. C7/N2/C8/O1/H1A/N1 and C7A/N2A/C8A/O1A/H1AA/N1A. The C═O bond length of 1.220 (3) Å is longer than the average C═O bond length (1.200 Å). These features are similar to those observed in the structure of N-benzoyl-N'-(3-pyridyl)thiourea (Dong et al., 2006). Bond lengths are in normal ranges (Allen et al., 1987).
In the crystal structure, intermolecular N-H···S hydrogen bonds (Table 1) link the molecules into a chain along the [110] (Fig 2).

Experimental
The title compound was synthesized according to a previously reported method (Hassan et al., 2008) with some modification.
Terephthaloyl chloride (1.015 g, 0.5 mmol) was added to ammonium thiocyanate (0.770 g, 1 mmol) in tetrahydrofuran and the contents were stirred for 10 min. The precipitated ammonium chloride was removed by filtration and then aniline (1.0 ml, 1 mmol) in methanol was added dropwise. The mixture was refluxed for 5 h and the black coloured solution was dried using a evaporator before it was washed with cool methanol. Yellow crystals of the title compound were obtained by recrystallization from DMF.

Refinement
H atoms were positioned geometrically [N-H = 0.86 Å and C-H = 0.93Å] and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (C,N). Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. Atoms labelled with the suffix A are generated by the symmetry operation (2-x, -y, 1-z).  as those based on F, and R-factors based on ALL data will be even larger.