Guidelines for Tuning the Excited State Hückel-Baird Hybrid Aromatic Character of Pro-Aromatic Quinoidal Compounds

30 December 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The present study aims to provide a solid ground for the identification, characterization and controlled design of pro-aromatic quinoidal organic compounds holding conjugated rings with Hückel and/or Baird (singlet and triplet) excited state aromatic character, and expects to become a reference work for future studies on Baird-aromaticity. Concretely, we explore a wide range of compounds with a central conjugated ring of different sizes and symmetric exocyclic substitutions. We employ a combination of different computational tools and we also introduce a new energy-based approach for the quantification of the Baird-aromatic character.

The key findings of this study indicate that Baird aromaticity is achieved in pro-aromatic quinoidal compounds having small anionic rings or in electron deficient rings with the proper exocyclic substitution. Low-lying states of these systems show very strong hole/electron overlaps, implying that their aromaticity cannot be related to intramolecular charge transfer.


excited states
charge transfer
conjugated rings

Supplementary materials

supp info


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