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

• DOI: 10.1016/j.tet.2016.01.017
• Publication Date: 2016-01-12T21:03:30Z
• Authors: Cagatay Dengiz; Céline Prange; Przemyslaw Gawel; Nils Trapp; Laurent Ruhlmann; Corinne Boudon; François Diederich
• Keywords: Chromophore; Chloranil

Abstract 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.