Molecular species having two unpaired electrons, in which at least two different electronic
states with different multiplicities [electron-paired (
singlet state) or electron-unpaired (
triplet state)] can be identified, e.g.
H2C.–CH2–C.H2
propane-1,3-diyl (trimethylene).
Source:
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1333