Halogen bond

Halogen bond (including halogen bridge ) is a non - covalent bond between a halogen (X ) (as Lewis acid) and a Lewis base (B). It is similar to the hydrogen bonding. The coming end of this bond for carrying electron acceptor property of the halogens is based on the sigma- hole, an unequal charge distribution ( anisotropy ) of these atoms. Applications of halogen bonding can be found in liquid crystals in the crystal technology, but also in many biological processes.

Most halogen bonds occur with iodine and bromine. However, there also exist some with fluorine and chlorine. The strength of a halogen bond is from 5 to 180 kJ / mol. In contrast to the hydrogen bond, the halogen bond is highly directional and has an optimum angle of 180 ° between RX · B, where R is the molecular residue which is linked to the halogen. The thickness of the halogen bond is also determined by the electronic properties of the substituents on X and B.

History

The first report of a XB- complex dates back to 1814 and described the adduct of iodine and ammonia, 1883 XB complexes have been described, resulting from larger molecules, such as Iodoform and quinoline, put together.