N,N′-Bis(4-fluorophenyl)urea

The asymmetric unit of the title compound, C13H10F2N2O, contains one and a half N,N′-bis(4-fluorophenyl)urea molecules. One of the molecules has crystallographic twofold rotation symmetry. The benzene rings are twisted from each other by dihedral angles of 29.69 (6)° for the molecule in a general position and 89.83 (6)° for the symmetry-generated molecule. In the crystal structure, a pair of intermolecular N—H⋯O hydrogen bonds link symmetry-related molecules into chains along the b axis, forming R 2 1(6) ring motifs.

The asymmetric unit of the title compound, C 13 H 10 F 2 N 2 O, contains one and a half N,N 0 -bis(4-fluorophenyl)urea molecules. One of the molecules has crystallographic twofold rotation symmetry. The benzene rings are twisted from each other by dihedral angles of 29.69 (6) for the molecule in a general position and 89.83 (6) for the symmetry-generated molecule. In the crystal structure, a pair of intermolecular N-HÁ Á ÁO hydrogen bonds link symmetry-related molecules into chains along the b axis, forming R 2 1 (6) ring motifs.

Comment
The synthesis of bis-arylureas has received considerable attention due to their wide range of biological applications. They act as potential Raf kinase inhibitors (Khire et al., 2004) and antagonists of human vanilloid receptor 1 (VR 1) (McDonnell et al., 2008). Phenyl thiazolylurea derivatives have been reported as inhibitors of Murine receptor A and Murine receptor B (Francisco et al., 2004). Some substituted ureas are used as antidiabetic and tranquilizing drugs, antioxidants in gasoline, corrosion inhibitor and herbicides (Bigi et al., 1998).
The asymmetric unit of the title compound ( Fig. 1), comprises of one and a half N,N'-bis-(4-fluorophenyl)urea molecules.
The half molecule has a twofold rotation symmetry, generated by symmetry code -x, y, -z+3/2. In the molecule with suffix A, both benzene rings (C1A-C6A and C8A-C13A) are twisted from each other with a dihedral angle of 29.69 (6)° whereas in molecule with suffix B, the dihedral angle between the benzene rings (C1B-C6B and C1BA-C6BA) is 89.83 (6)°. The structure is comparable to the related structure (Jai-nhuknan et al., 1997).
The remaining H atoms were positioned geometrically [C-H = 0.93 Å] and were refined using a riding model, with U iso (H) = 1.2 U eq (C). In the final difference Fourier map, the highest peak is 0.20 Å from atom O1B and the deepest hole is 0.45 Å from atom C7B.   supplementary materials sup-3 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 > σ(F 2 ) is used only for calculating Rfactors(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.