Y-shaped AIEE active quinoxaline-benzothiazole conjugate for fluorimetric sensing of nitroaromatics in aqueous media

Abstract

Three novel Y-shaped dimer quadrupolar A(-D-A)2 derivatives with quinoxaline and benzothiazole rings as the acceptors and biphenyl ring as the donor were synthesized in good yields by simple condensation reaction. Twisted structure along with herringbone packing arrangement for QB1 was depicted by single crystal X-ray diffraction studies. Aggregation induced emission enhancement (AIEE) was exhibited by all in THF-Water mixture. Naked eye colour change from colourless to yellow upon addition of picric acid accompanied with quenching of emission intensity was observed for all in aqueous as well as in THF solution. Detection limits of the probes towards picric acid were found in the submicromolar range. Large spectral overlap between absorption spectra of picric acid and emission spectra of probes depicted energy transfer as plausible fluorescence quenching mechanism. Further, the 1:2 binding stoichiometry of the probes towards picric acid was determined by Job’s plot. Filter paper strips for picric acid sensing were also fabricated. These novel compounds were also able to detect volatile acids like trifluoroacetic acid (TFA).