6-Iodo-4-oxo-4H-chromene-3-carbaldehyde

In the title compound, C10H5IO3, an iodinated 3-formylchromone derivative, the non-H atoms are essentially coplanar (r.m.s. deviation = 0.0259 Å), with the largest deviation from the least-squares plane [0.056 (5) Å] being found for the formyl O atom. In the crystal, molecules are linked through I⋯O halogen bonds [I⋯O = 3.245 (4) Å, C—I⋯O = 165.95 (13) and C=O⋯I = 169.7 (4)°] along [101]. The supramolecular chains are assembled into layers via π–π stacking interactions along the b axis [shortest centroid–centroid distance between the pyran and benzene rings = 3.558 (3) Å].


Structural commentary
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, Sirimulla et al., 2013. We have recently reported the crystal structures of monohalogenated 3-formylchromone derivatives 6-fluoro-4-oxo-4H-chromene-3-carbaldehyde (Ishikawa, 2014c,  Fig.·3C). It was found that halogen bond is formed between the formyl oxygen atom and the bromine atom in the bromo derivative, but is not formed in the others light-atom derivatives. As part of our interest in this type of chemical bonding, we herein report the crystal structure of a monoiodinated 3-formylchromone derivative 6iodo-4-oxo-4H-chromene-3-carbaldehyde. The objective of this study is to reveal whether halogen bond(s) can be formed in the crystal structure of the title compound with the iodine atom in the 6-position.
The mean deviation of the least-squares plane for the non-hydrogen atoms is 0.0259 Å, and the largest deviation is 0.056 (5) Å for C10. These mean that these atoms are essentially coplanar (Fig. 1).
In the crystal, the molecules are stacked with the inversion-symmetry equivalents along the b axis [shortest centroidcentroid distance between the pyran and benzene i rings of the 4H-chromene units = 3.588 (3) Å, i: -x + 1, -y + 2, -z], as shown in Fig. 1.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq I1 0.09130 (