Crystal structure of 4,5-dibromophenanthrene

Abstract

The synthesis and crystal structure of the title compound, C14H8Br2, is described. The molecule is positioned on a twofold rotation axis and the asymmetric unit consists of half a molecule with the other half being generated by symmetry. The presence of two large bromine atoms in the bay region significantly distorts the molecule from planarity and the mean planes of the two terminal rings of the phenanthrene system are twisted away from each other by 28.51 (14)°. The torsion angle between the two C—Br bonds is 74.70 (14)° and the distance between the two Br atoms is 3.2777 (13) Å. The molecules pack in layers in the crystal, with the centroids of the central rings of the phenanthrene units in adjacent layers separated by a distance of 4.0287 (10) Å. These centroids are shifted by 2.266 (6) Å relative to each other, indicating slippage in the stacking arrangement. Furthermore, the distance between the centroids of the terminal and central rings of the phenanthrene units in adjacent layers is slightly shorter at 3.7533 (19) Å. While all of the molecules within each layer are oriented in the same direction, those in adjacent layers are oriented in the opposite direction, leading to anti-parallel stacks.

Keywords

• crystal structure
• polycyclic aromatic hydrocarbon
• helical molecule