CC BY 4.0 UnportedIntorp, S.N.Hodecker, M.Müller, M.Tverskoy, O.Rosenkranz, M.Dmitrieva, E.Popov, A.A.Rominger, F.Freudenberg, J.Dreuw, A.Bunz, U.H.F.2020-07-172020-07-172020https://doi.org/10.34657/3556https://oa.tib.eu/renate/handle/123456789/4927Quinoidal azaacenes with almost pure diradical character (y=0.95 to y=0.99) were synthesized. All compounds exhibit paramagnetic behavior investigated by EPR and NMR spectroscopy, and SQUID measurements, revealing thermally populated triplet states with an extremely low-energy gap ΔEST′ of 0.58 to 1.0 kcal mol−1. The species are persistent in solution (half-life≈14–21 h) and in the solid state they are stable for weeks.enghttps://creativecommons.org/licenses/by/4.0/540acenesheteroaromaticsradicalsstructure elucidationsynthetic methodsNuclear magnetic resonance spectroscopyDiradicalsHalf livesParamagnetic behaviorSQUID measurementsTriplet stateElectron spin resonance spectroscopyArticle