Synthesis, complexation, and fluorescence behavior of 3,4-dimethylthieno[2,3-b]thiophene carrying two monoaza-15-crown-5 ether groups

A novel fluoroionophore 1 based on 3,4-dimethylthieno[2,3-b]thiophene bearing two monoaza-15-crown-5 ethers at 3- and 4-positions was prepared. UV–vis and fluorescence responses of compound 1 upon the addition of alkali and alkaline earth metal cations were evaluated in acetonitrile solution. Receptor 1 showed unique response for Ba2+ due to the formation of an intramolecular sandwich complex.

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► We reported that a novel fluorescent chemosensor 1 of 3,4-dimethylthieno[2,3-b]-thiophene bearing two aza-15-crown-5 moieties at 3- and 4-positions.
► Fluorescent chemosensor 1 displays a strong fluorescence enhancement upon interaction with Ba2+.
► This selective enhancement of 1 is ascribed to the formation of the intramolecular sandwich complex.