Antiaromatic 1,5-Diaza-s-indacenes.
Angew Chem Int Ed Engl
; 60(38): 20765-20770, 2021 Sep 13.
Article
em En
| MEDLINE
| ID: mdl-34288340
ABSTRACT
s-Indacene is a classical non-alternant hydrocarbon that contains 12 π-electrons in a cyclic π-conjugation system. Herein, we report its nitrogen-doped analogue, 1,5-diaza-s-indacene. 1,5-Diaza-s-indacenes were readily prepared from commercially available 2,5-dichlorobenzene-1,4-diamine through a two-step transformation consisting of a palladium-catalyzed Larock cyclization with diaryl acetylenes followed by hydrogen abstraction. The thus obtained 1,5-diaza-s-indacenes exhibited distinct antiaromaticity, as manifested in clear bond-length alternation, a forbidden HOMO-LUMO transition, and a paratropic ring current. As compared to the parent s-indacene, the 1,5-diaza-s-indacenes showed higher electron-accepting ability owing to the presence of imine-type nitrogen atoms. The 1,5-diaza-s-indacene core is effectively conjugated with the peripheral aryl groups, which enables fine-tuning of the absorption spectra and redox properties. The two possible localized forms of 1,5-diaza-s-indacene were compared in terms of their energetic aspects.
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MEDLINE
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En
Ano de publicação:
2021
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Article