Redistribution of the
valence-shell
electron density throughout a molecular entity as compared with some localized models (individual atoms in their
valence states, separated bonds or fragments). Different topological modes of the electron
delocalization include:
- ribbon delocalization of either π- or σ-electrons (i.e., electrons occupying respectively π- and σ-orbitals)
- surface delocalization of σ-electrons occurring through an overlap of radially oriented
σ-orbitals of a cyclic molecule, as is the case of cyclopropane; and
-
volume delocalization of σ-electrons through an overlap of
σ-orbitals directed inside a molecular polyhedron, as is the case in tetrahedrane.
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