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Twofold 6π‐Electrocyclization as a Route Toward Multi‐Heteroatom‐Doped Nanographenes Built on a 1,4‐Dihydropyrrolo[3,2‐b]pyrrole Core

Year: 2024

Type: article

Abstract: Here we present a highly versatile synthetic strategy based on twofold 6π-electrocyclization accompanied with HBr elimination as a novel approach towards centrosymmetric multi-heteroatom-doped nanographenes build around an electron-rich 1,4-dihydropyrrolo[3,2-b]pyrrole core. A straightforward synthesis from readily available substrates offers a unique possibility of fusing the 1,4-dihydropyrrolo[3,2-b]pyrrole subunit not only with carbocyclic building blocks, such as electron-deficient phenanthrenes, chrysenes, or [4]helicenes, but also with heterocyclic systems, such as benzo[b]furan and 5-thiatruxene. The clear advantage of this strategy is that there is no requirement to assemble complex scaffolds possessing bromoaryl units since bromine atom is introduced by bromination of 1,4-dihydropyrrolo[3,2-b]pyrrole core which, because of its exceptionally electron-rich character, is straightforward reaction. The obtained χ-shaped and S-shaped nanographenes containing 10 or more fused rings, exhibit visible-range emissions characterized by fluorescence quantum yields reaching 48 %. Computational studies of the reaction mechanism revealed that the 6π-electrocyclization is kinetically favourable over photo-induced direct arylation. Steady-state UV/Visible spectroscopy reveals that upon photoexcitation, the prepared S-shaped N-doped nanographenes undergo mostly radiative relaxation leading to large fluorescence quantum yields. We anticipate that this chemistry will empower the creation of new materials with various functionalities.

Source: Chemistry - A European Journal

DOI: 10.1002/chem.202404094

Authors: Krzysztof Górski, Ljupcho Pejov, Kåre B. Jørgensen, Iryna Knysh, Denis Jacquemin, Daniel T. Gryko