Air stable high-spin blatter diradicals: non-Kekule versus Kekule structures

摘要

Air stable high-spin diradicals under ambient conditions are relatively rare. We report two 1,2,4-benzotriazinyl based diradicals, non-Kekule ' o-DBT and Kekule ' p-DBT, with a highly twisted bridge. The studies of magnetic susceptibilities reveal that both diradicals possess singlet ground states and small singlet-triplet energy gaps (DEs-t = 0.21 and 0.18 kcal mol 1 for o-DBT and p-DBT, respectively), leading to a thermal accessible triplet excited state. Furthermore, variable-temperature electron spin resonance discloses that the average distance between the two spin centers of o-DBT and p-DBT increases with increasing temperature. Finally, both diradical molecules show very high stabilities under high power irradiation and thermal treatment. In particular, the powder of o-DBT exhibits excellent thermal stability up to 270 1C without noticeable decomposition.