6,8-Dichloro-4-oxochromene-3-carbaldehyde

The asymmetric unit of the title compound, C10H4Cl2O3, contain two essentially planar independent molecules (mean atomic deviations from the corresponding least-square planes are 0.041 and 0.045 Å for molecules 1 and 2, respectively). In the crystal, molecules are linked through a pair of halogen bonds [Cl⋯O separations are 3.044 (5) and 3.033 (6) Å, C—Cl⋯O angles are 160.4 (3) and 162.8 (3)°, and C=O⋯Cl angles are 138.7 (4) and 139.6 (4)°, respectively, in molecules 1 and 2] and C—H⋯O hydrogen bonds into slightly folded bands [the dihedral angle between the planes of neighboring molecules is 8.6 (2)°] along the c-axis direction.


2012).
The title compound, C 10 H 4 Cl 2 O 3 , crystallizes with two independent molecules in the asymmetric unit (Fig. 1). The mean deviations from the least-square planes for all atoms of molecule 1 and 2 are 0.0410 Å and 0.0449 Å, respectively. In addition, the largest deviations of molecule 1 and 2 are 0.1512 (17) Å for Cl1a and -0.0973 Å for H4b, respectively. This means that all atoms of each molecule are essentially coplanar.
Halogen bonds have been found to occur in organic, inorganic, and biological systems, and have recently attracted much attention in medicinal chemistry, chemical biology, and supramolecular chemistry (Auffinger et al. 2004, Metrangolo et al. 2005, Wilcken et al. 2013. Our analysis suggests that the strong inhibitory activity of the title compound against urease may be attributable to the halogen bond observed in the crystal, because 3-formylchromones without any halogen atom at the 8-position in the literature do not show the urease inhibitory activity (Kawase et al. 2007).

Experimental
Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a 2-butanone solution of commercially available 6,8-dichloro-3-formylchromone at room temperature.

Refinement
The C(sp 2 )-bound hydrogen atoms were placed in geometrical positions [C-H 0.95 Å, U iso (H) = 1.2U eq (C)], and refined using a riding model.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.
Hydrogen atoms are shown as small spheres of arbitrary radius.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.70 e Å −3 Δρ min = −0.79 e Å −3 Special details Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).

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