Delocalized electron

From delocalization (often π -electron system ) is spoken in the chemistry when one or more electrons in an atom group, ie a molecule or molecular ion, not exactly localized, but is distributed over the individual atoms. For a description of this charge distribution according to VB theory is used mesomeric structures.

A special case of delocalized charges can be found in conjugated systems of aromatic compounds. Their π - electrons are not in isolated, two carbon atoms corresponding π orbitals localized, but belong to molecular orbitals that extend over several carbon atoms; the π - electrons are distributed in an " electron cloud ," in relation to carbon atoms of the total aromatic system. A classic example of such an aromatic molecule with delocalized π - electrons is benzene. The ring structure of benzene in 1865 ( fr. Article ) (German article 1866) and the limiting structures postulated in 1872 by Kekulé correctly.

Molecules or metal complexes with large delocalized electron systems are often colored, as organic compounds, such as carotenoids or charge-transfer complexes, such as potassium permanganate. Other examples are sandwich complexes such as ferrocene and titanocene.