Theoretical calculations reveal that five-membered cyclic species with “hyperconjugative” aromaticity (and antiaromaticity) in the S₀ state will become antiaromatic (and aromatic) in the T₁ state (aromaticity is denoted by a delocalized large semicircle in the picture), in line with Baird's rule. In addition, NICS criterion and charge effects on triplet state aromaticity are also discussed. More information can be found in the Full Paper by Jun Zhu et al. (DOI:10.1002/asia.201500897).

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