Isolable Bis‐BN‐Based Analogues of Müller's Hydrocarbon.

Comprehensive Summary: Müller's hydrocarbon and its analogues are classical examples of Kekulé diradicaloids and have gained great attention. However, because of their high reactivities, their isolation and structural characterizations are still challenging. Herein, we report the isolation of two bis‐BN‐based analogues of Müller's hydrocarbon (1 and 2) as crystalline solids in moderate yields. Experimental results and theoretical studies demonstrated that compound 1 possessing the terminal 1,3,2‐diazaboryl groups is an open‐shell singlet diradicaloid, which is in contrast to the closed‐shell singlet ground states of the bis‐BN‐based analogues of Thiele's and Chichibabin's hydrocarbons with the same terminal groups, illustrating the strong influence of the central linkers on the ground state. Additionally, the replacement of the terminal 1,3,2‐diazaboryl groups in 1 with the bis(2,4,6‐triisopropylphenyl)boryl groups affords 2 with higher diradical character and a smaller singlet‐triplet energy gap. [ABSTRACT FROM AUTHOR]