A Stable Triplet‐Ground‐State Conjugated Diradical Based on a Diindenopyrazine Skeleton

• Published in: Angewandte Chemie International Edition Vol. 60; no. 9; pp. 4594 - 4598
• Main Authors: Wang, Zi‐Yuan, Dai, Ya‐Zhong, Ding, Li, Dong, Bo‐Wei, Jiang, Shang‐Da, Wang, Jie‐Yu, Pei, Jian
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 23.02.2021; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Chemistry; Chemistry, Multidisciplinary; conjugated radicals; Density; high-spin; Magnetic materials; Nitrogen atoms; Physical Sciences; Pyrazine; Radicals; Science & Technology; singlet–triplet gap; Spintronics; stable radicals; pyrazine; SHELL; singlet-triplet gap; M-XYLYLENE; conjugated radicals; stable radicals; ORGANIC RADICALS; ANTHRACENE; HYDROCARBON; high-spin
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202012989

High‐spin conjugated radicals have great potential in magnetic materials and organic spintronics. However, to obtain high‐spin conjugated radicals is still quite challenging due to their poor stability. We report the successful synthesis and isolation of a stable triplet conjugated diradical, 10,12‐diaryldiindeno[1,2‐b:2′,1′‐e]pyrazine (m‐DIP). With the m‐xylylene analogue skeleton containing electron‐deficient sp2‐nitrogen atoms, m‐DIP displays significant aromatic character within its pyrazine ring and its spin density mainly delocalizes on the meta‐pyrazine unit, making it a triplet ground state conjugated diradical. Our work provides an effective “spin density tuning” strategy for stable high‐spin conjugated radicals. A stable triplet‐ground‐state conjugated diradical with pyrazine as a linker group was synthesized with a half‐life time of about 22 days under ambient conditions. The electron‐deficient pyrazine unit impedes spin delocalization to the peripheral phenyl rings, which increases the spin density distribution on the central meta‐pyrazine unit, leading to a large ΔES‐T.