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Issue 12, 2018
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Triplet state homoaromaticity: concept, computational validation and experimental relevance

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Abstract

Cyclic conjugation that occurs through-space and leads to aromatic properties is called homoaromaticity. Here we formulate the homoaromaticity concept for the triplet excited state (T1) based on Baird's 4n rule and validate it through extensive quantum-chemical calculations on a range of different species (neutral, cationic and anionic). By comparison to well-known ground state homoaromatic molecules we reveal that five of the investigated compounds show strong T1 homoaromaticity, four show weak homoaromaticity and two are non-aromatic. Two of the compounds have previously been identified as excited state intermediates in photochemical reactions and our calculations indicate that they are also homoaromatic in the first singlet excited state. Homoaromaticity should therefore have broad implications in photochemistry. We further demonstrate this by computational design of a photomechanical “lever” that is powered by relief of homoantiaromatic destabilization in the first singlet excited state.

Graphical abstract: Triplet state homoaromaticity: concept, computational validation and experimental relevance

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Publication details

The article was received on 22 Nov 2017, accepted on 16 Feb 2018 and first published on 19 Feb 2018


Article type: Edge Article
DOI: 10.1039/C7SC05009G
Citation: Chem. Sci., 2018,9, 3165-3176
  • Open access: Creative Commons BY license
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    Triplet state homoaromaticity: concept, computational validation and experimental relevance

    K. Jorner, B. O. Jahn, P. Bultinck and H. Ottosson, Chem. Sci., 2018, 9, 3165
    DOI: 10.1039/C7SC05009G

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