Preferred Label : biradical;
IUPAC definition : An even-electron molecular entity with two (possibly delocalized) radical centres
which act nearly independently of each other, e.g. Species in which the two radical
centres interact significantly are often referred to as 'biradicaloids'. If the two
radical centres are located on the same atom, the species are more properly referred
to by their generic names: carbenes, nitrenes, etc. The lowest-energy triplet state
of a biradical lies below or at most only a little above its lowest singlet state
(usually judged relative to kB.T, the product of the Boltzmann constant kB and the
absolute temperature T). The states of those biradicals whose radical centres interact
particularly weakly are most easily understood in terms of a pair of local doublets.
Theoretical descriptions of low-energy states of biradicals display the presence of
two unsaturated valences (biradicals contain one fewer bond than permitted by the
rules of valence): the dominant valence bond structures have two dots, the low energy
molecular orbital configurations have only two electrons in two approximately nonbonding
molecular orbitals, two of the natural orbitals have occupancies close to one, etc.
Although this term has been recommended in the past for diradicals, specialists working
in the field prefer the latter term.;
Origin ID : B00671;
Automatic exact mappings (from CISMeF team)
- See also
An even-electron molecular entity with two (possibly delocalized) radical centres
which act nearly independently of each other, e.g. Species in which the two radical
centres interact significantly are often referred to as 'biradicaloids'. If the two
radical centres are located on the same atom, the species are more properly referred
to by their generic names: carbenes, nitrenes, etc. The lowest-energy triplet state
of a biradical lies below or at most only a little above its lowest singlet state
(usually judged relative to kB.T, the product of the Boltzmann constant kB and the
absolute temperature T). The states of those biradicals whose radical centres interact
particularly weakly are most easily understood in terms of a pair of local doublets.
Theoretical descriptions of low-energy states of biradicals display the presence of
two unsaturated valences (biradicals contain one fewer bond than permitted by the
rules of valence): the dominant valence bond structures have two dots, the low energy
molecular orbital configurations have only two electrons in two approximately nonbonding
molecular orbitals, two of the natural orbitals have occupancies close to one, etc.
Although this term has been recommended in the past for diradicals, specialists working
in the field prefer the latter term.
