semiquinones

https://doi.org/10.1351/goldbook.S05600
Radical anions having the structure O–Z–O. where Z is an ortho- or para-arylene group or analogous heteroarylene group; they are formally generated by the addition of an electron to a @Q05015@.
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1365 [Terms] [Paper]