title: Crystal structure of 7,8-di-chloro-4-oxo-4H-chromene-3-carbaldehyde.
abstract: In the title compound, C10H4Cl2O3, a dichlorinated 3-formyl-chromone derivative, the fused-ring system is slightly puckered [dihedral angle between the benzene and pyran rings = 3.66 (10)°]. The dihedral angle between the pyran ring and the formyl plane is 8.64 (7)°. In the crystal, mol-ecules are linked through π-π stacking inter-actions [centroid-centroid distance between the benzene and pyran rings = 3.727 (2) Å], C-H⋯O hydrogen bonds and short C⋯O contacts [2.838 (4) Å]. Halogen bonds between the formyl O atoms and the Cl atoms at the 7-position [Cl⋯O = 2.984 (3) Å, C-Cl⋯O = 170.83 (12)° and Cl⋯O-C = 116.05 (19)°] are also formed along the a axis, resulting in helical structures constructed by C-H⋯O hydrogen bonds and Cl⋯O halogen bonds along the b axis. In addition, type II halogen-halogen contacts between the chlorine atoms at the 7- and 8-positions [Cl⋯Cl = 3.519 (2) Å, C-Cl⋯Cl = 171.24 (10)° and 88.74 (11)°] are observed.
authors.affiliation: School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Ishikawa
keywords: crystal structure; halogen bond; halogen–halogen inter­action; hydrogen bond; π–π stacking