Analysis of a Compound Class with Triplet States Stabilized by Potentially Baird Aromatic [10]Annulenyl Dicationic RingsShow others and affiliations
2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 8, p. 2793-2800Article in journal (Refereed) Published
Abstract [en]
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 8π-electron methano[10]annulene (M10A) dicationic ring and 2) a Hückel aromatic with a neutral closed-shell 10π-electron ring. According to charge and spin density distributions, the Hückel aromatic structure dominates the triplet state (the Baird aromatic contributes at most 12 %), and separation of the aromatic fluctuation index (FLU) into α and β electron contributions emphasizes this finding. The small singlet-triplet energy gap is due to Hückel aromaticity of the M10A ring, clarified by comparison to the smaller analogues of TMTQ. Yet, TMTQ and its analogues are Hückel-Baird hybrids allowing for tuning between closed-shell 4n+2 Hückel aromaticity and open-shell 4n Baird aromaticity.
Place, publisher, year, edition, pages
Wiley-VCH Verlag , 2016. Vol. 22, no 8, p. 2793-2800
Keywords [en]
annulenes, aromaticity, Baird's rule, diradical species, electronic structure, Aromatic compounds, Quantum chemistry, Quantum theory, Aromatic fluctuation index, Aromatic structures, Aromaticities, Diradicals, Singlet-triplet energy gap, Spin density distributions, Aromatization
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:ri:diva-57310DOI: 10.1002/chem.201504924Scopus ID: 2-s2.0-84958279552OAI: oai:DiVA.org:ri-57310DiVA, id: diva2:1616688
2021-12-032021-12-032021-12-03Bibliographically approved