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Quinoidal 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. [ABSTRACT FROM AUTHOR]

Chem. 30/2020) Keywords: acenes; heteroaromatics; radicals; structure elucidation; synthetic methods EN acenes heteroaromatics radicals structure elucidation synthetic methods 12644 12644 1 07/15/20 20200720 NES 200720 B Diradikal-Puzzle b Der Zusammenbau der richtigen Kombination aus einem Azaacen, Phenoxylgruppen und Dithienobenzol-Regioisomeren wird mit chinoidalen Azacenen mit nahezu reinem Diradikalcharakter belohnt, die im festen Zustand über Wochen stabil und auch in Lösung haltbar sind. Acenes, heteroaromatics, radicals, structure elucidation, synthetic methods. [Extracted from the article]