6-Chloro-7-fluoro-4-oxo-4H-chromene-3-carbaldehyde

In the title compound, C10H4ClFO3, a chlorinated and fluorinated 3-formylchromone derivative, all atoms are essentially coplanar (r.m.s. = 0.0336 Å for the non-H atoms), with the largest deviation from the least-squares plane [0.062 (2) Å] being for a benzene-ring C atom. In the crystal, molecules are linked through stacking interactions [centroid–centroid distance between the benzene and pyran rings = 3.958 (3) Å and interplanar distance = 3.259 (3) Å], C—H⋯O hydrogen bonds, and short C⋯O contacts [2.879 (3) Å]. Unsymmetrical halogen–halogen interactions between the Cl and F atoms [Cl⋯F = 3.049 (3) Å, C—Cl⋯F = 148.10 (9)° and C—F⋯Cl = 162.06 (13)°] are also formed, giving a meandering two-dimensional network along the a axis.

I acknowledge the University of Shizuoka for instrumental support.
Supporting information for this paper is available from the IUCr electronic archives (Reference: ZL2593).
The mean deviation of the least-square planes for the non-hydrogen atoms is 0.0336 Å, and the largest deviations is 0.062 (2) Å for C4. These mean that these atoms are essentially coplanar (Fig.1).
In the crystal, the molecules are linked through stacking interaction between the translation-symmetry equivalent i molecules [centroid-centroid distance between the benzene and pyran rings of the 4H-chromene units = 3.958 (3) Å, interplanar distance 3.259 (3) Å, i: x, y, z + 1], and through C-H···O hydrogen bonds (see hydrogen bonding table).
A contact between the formyl oxygen atom and the chlorine atom at 6-position is not found in the title compound.
Furthermore, short contacts between the formyl C10 and O3 ii atoms [2.879 (3) Å, ii: -x + 1/2, -y + 1, z + 1/2] are observed. This interesting feature might be caused by strong dipole-dipole interaction between the formyl groups polarized by introduction of the chlorine and fluorine atoms into the chromone ring. These findings should be helpful to understand interaction of halogenated ligands with proteins, and are thus valuable for rational drug design.
The precipitates were collected, washed with water, and dried in vacuo (yield: 58% 226.991, found 227.014. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of an ethyl acetate/chloroform solution of the title compound 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.