semiquinones

https://doi.org/10.1351/goldbook.S05600
Radical anions having the structure Oāˆ’ā€“Zā€“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 quinone.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1365 (https://doi.org/10.1351/pac199567081307)