Analysis of a Compound Class with Triplet States Stabilized by Potentially Baird Aromatic Annulenyl Dicationic Rings
2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 8, 2793-2800 p.Article in journal (Refereed) PublishedText
The low-lying triplet state of a recently published compound (TMTQ) was analyzed quantum chemically in light of suggestions that it is influenced by Baird aromaticity. Two mesomeric structures describe this state: 1)a zwitterionic Baird aromatic structure with a triplet diradical 8-electron methanoannulene (M10A) dicationic ring and 2)a Huckel aromatic with a neutral closed-shell 10-electron ring. According to charge and spin density distributions, the Huckel aromatic structure dominates the triplet state (the Baird aromatic contributes at most 12%), and separation of the aromatic fluctuation index (FLU) into and electron contributions emphasizes this finding. The small singlet-triplet energy gap is due to Huckel aromaticity of the M10A ring, clarified by comparison to the smaller analogues of TMTQ. Yet, TMTQ and its analogues are Huckel-Baird hybrids allowing for tuning between closed-shell 4n+2 Huckel aromaticity and open-shell 4n Baird aromaticity.
Place, publisher, year, edition, pages
2016. Vol. 22, no 8, 2793-2800 p.
annulenes, aromaticity, Baird's rule, diradical species, electronic structure
IdentifiersURN: urn:nbn:se:uu:diva-281795DOI: 10.1002/chem.201504924ISI: 000370193000029PubMedID: 26791436OAI: oai:DiVA.org:uu-281795DiVA: diva2:915603
FunderSwedish Research Council, 621-2011-4177