Push–pull chromophores by reaction of 2,3,5,6-tetrahalo-1,4-benzoquinones with 4-(N,N-dialkylanilino)acetylenes

A series of new push–pull chromophores were synthesized from electron-rich 4-(N,N-dialkylanilino)acetylenes and 2,3,5,6-tetrahalo-1,4-benzoquinones. The reactivity of the latter differs substantially from that of the previously investigated 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The transformation with fluoranil gave orange-colored, bis-donor-substituted chromophores with a tricyclic, cyclobutene-fused dihydrobenzofuranone core. In contrast, the reaction with chloranil yielded mono-donor-substituted, blue 1,4-benzoquinone-based chromophores, which were further reacted with tertiary amines to form bis-donor-substituted push–pull systems. The structures of the new chromophores were confirmed by X-ray analysis, and mechanisms for their formation are proposed. They feature intense intramolecular charge-transfer bands in the visible region, and their optoelectronic properties were investigated by UV/Vis spectroscopy, electrochemistry, and computational analysis.

A simple, short synthesis of bis-donor substituted push–pull chromophores featuring quinone-derived acceptors was developed starting from easily accessible dialkylanilino- (DAA) substituted alkynes and haloquinones. Fluoranil and chloranil displayed significant reactivity differences, leading to very different chromophore structures. The new chromophores feature promising intramolecular charge-transfer properties and can be tuned for potential use in optoelectronic devices. The low-intensity charge-transfer absorption bands in previously reported homoconjugated push–pull chromophores obtained by [2+2] cycloaddition of DDQ and aniline-substituted alkynes were strongly enhanced upon introduction of additional, linearly π-conjugated donor groups. These findings are further corroborated by density functional theory calculations.Figure optionsDownload high-quality image (137 K)Download as PowerPoint slide