Nitrogen-coupled blatter diradicals: the fused versus unfused bridges

Abstract

We report the synthesis and characterization of nitrogen-coupled diradicals NDR (unfused) and CDR (fused). NDR has a large diradical character y of 0.89, and a small singlet–triplet energy gap ΔE_S–T of −1.16 kcal mol⁻¹ with the observation of a forbidden transition signal (Δm_s = ±2). Moreover, NDR shows very high stability. In contrast, the fused CDR has a smaller y (0.68), along with a larger ΔE_S–T (−2.38 kcal mol⁻¹).