Photoswitchable dihetarylethene chemosensors for the selective 'naked-eye' detection of fluoride anions

Novel photochromic thiazole-bridged dihetarylethenes with coumarinyl and thiophenyl substituents were synthesized. Their interaction either in ring-opened or in cyclic forms with fluoride, cyanide or acetate anions leads to drastic visibly detected changes in the electronic absorption spectra (yellow-to-violet color change), whereas other anions (Cl−, Br−, I−, SCN−, NO3−, HSO4− and H2PO4−) do not induce any considerable colorimetric changes. Only in the case of fluoride ions, this effect is accompanied by very fast consecutive bleaching of solutions (violet-to-yellowish color change) owing to irreversible deprotonation of the NH moiety. This mechanism is supported by the results of the DFT calculations.

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