D-π-A benzo[c][1,2,5]selenadiazole-based derivatives via an ethynyl bridge: Photophysical properties, solvatochromism and applications as fluorescent sensors

•Synthesis and characterization of novel D-π-A benzo[c][1,2,5]selenadiazole-based derivatives.•The new compounds exhibit positive solvatochromism.•The band gaps of the new compounds are in the range of 2.21–2.70 eV.•Application as fluorescent sensors using benzo[c][1,2,5]selenadiazole as an acceptor or a fluorophore.

A series of novel D-π-A benzo[c][1,2,5]selenadiazole (BSe)-based derivatives 7a–i including electron-donating/electron-withdrawing groups were prepared by Pd-catalyzed Sonogashira–Hagihara reaction of 4,7-diethynylbenzoselenadiazole with various diiodo aryl compounds. Photophysical properties of these compounds were investigated by absorption and emission spectra analyses. Compound 7c containing methoxy group exhibited positive solvatochromism and its solvatochromic properties were analyzed by the Lippert–Mataga equation and Kamlet–Taft equation, respectively. The resulting compounds showed tunable band gaps in the range of 2.21–2.70 eV using theoretical calculations, which was in good agreement with the results derived from the absorption of UV–vis spectra. In addition, fluorescent sensors 7c and 7d showed highly sensitive response for Hg2+ and traces of water using BSe as an acceptor or a fluorophore in real-time detection, respectively. These findings indicate that BSe-based molecules can be developed as excellent fluorophores for fluorescent material applications.

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