Understanding the nature of quinoidal and zwitterionic states in carbazole-based diradicals†
Abstract
We report two carbazole-based diradicals, out of which the m-isomer shows a large diradical character y0 (0.89) and a small singlet–triplet energy gap ΔES–T (−0.98 kcal mol−1), whereas the p-isomer exhibits smaller y0 (0.79) but a much larger ΔES–T (−6.16 kcal mol−1). DFT calculations reveal that this tendency is also suitable for nitrogen and carbon-centered diradicals.