6,8-Diiodo-4-oxo-4H-chromene-3-carbaldehyde

The title compound, C10H4I2O3, is an iodinated 3-formylchromone derivative, and the atoms are essentially coplanar [r.m.s. deviation = 0.049 Å, largest deviation from the least-squares plane = 0.111 (9) Å for the CH(=O) C atom]. In the crystal, molecules are linked into a three-dimensional network through halogen bonds [I⋯O = 3.352 (5) and 3.405 (7) Å, C—I⋯O = 144.2 (3) and 154.5 (3)°, and C=O⋯I = 134.9 (6) and 146.0 (6)°], and π–π stacking interactions [centroid–centroid distance = 3.527 (6) Å].


Experimental
We acknowledge the University of Shizuoka for instrumental support.
Supporting information for this paper is available from the IUCr electronic archives (Reference: ZL2583).
The mean deviation of the least-square planes for the non-hydrogen atoms is 0.0487 Å, and the largest deviations is 0.111 (9) Å for C10. These mean that the atoms are essentially coplanar.

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. There are large positive and negative electron densities around the iodine atoms in spite of the good R value. The reflection data were collected separately with a smaller sized crystal, but it is found that the large residual electron densities around the iodine atoms still remained. For most of the disagreeable reflections in the SHELX.lst file, F obs is much greater than F calc . This suggests the possibility of non-merohedral twinning. Thus, the large residual electron densities could be derived from non-merohedral twinning. Unfortunately, it is difficult to confirm the possibility on a single point detector diffractometer, Rigaku AFC7R. One reflection (-2 7 3) was omitted because of systematic error.
Extinction correction was applied for improvement of large negative electron densities and the R value.