Halogen bond
The halogen bond (also 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 bond . The electron acceptor property of the halogens that comes into play in this bond is based on the sigma hole , an uneven charge distribution ( anisotropy ) on these atoms. The halogen bond is used in liquid crystals , in crystal technology, but also in many biological processes.
Most halogen bonds occur with iodine and bromine . However, there are also some with fluorine and chlorine . The strength of a halogen bond ranges from 5 to 180 kJ / mol. In contrast to the hydrogen bond, the halogen bond is highly directional and has an optimal angle of 180 ° between RX ·· B, where R is the molecular residue that is connected to the halogen. The strength of the halogen bond is partly determined by the electronic properties of the substituents on X and B.
history
The first report on an XB complex dates back to 1814 and described the adduct of iodine and ammonia. In 1883, XB complexes were described, which are composed of larger molecules, e.g. B. iodoform and quinoline .
literature
- P. Metrangolo, G. Resnati, Halogen Bonding: Fundamentals and Applications. Springer-Verlag, 2007, ISBN 978-3-540-74329-3 . (Abstract)
Individual evidence
- ^ Halli, J .; Manolikakes, G .; Nachrichten aus der Chemie 2016, 64, 131–134: When holes strengthen bonds: the halogen bonds.
- ↑ M. Colin In: Ann. Chim. Volume 91, 1814, p. 252.
- ^ O. Roussopoulos In: Reports of the German Chemical Society . Volume 16, 1883, p. 202.