Michael addition-based colorimetric and fluorescence chemodosimeters for the nanomolar-level tracking of cyanide ions in aqueous-organic media

• Michael addition based chemodosimeters were synthesized to sense CN−.
• The sensing of CN− ion has been attributed due to the restriction of PET transition.
• These chemodosimeters R1 & R2 have been sense CN− up to trace level (10−9 M).

Two new naphthalimide-based chemodosimeters, R1 and R2, for CN− anions were designed and synthesized. For the sensing event, the dicyanovinyl group and ethyl cyanoacrylate groups acted as the recognition sites in conjunction with the electron-withdrawing naphthalimide fluorophore group. Both receptors exhibited high sensitivity and selectivity, with apparent response signals that could be observed by the naked eye, even in the presence of various other interference anions. We used electronic and fluorescent spectroscopic techniques, NMR titration measurements and HRMS techniques to rationalize the sensing mechanisms of these two receptors. Upon the addition of CN−, the fluorescence of R1 and R2 was distinctly enhanced. Specifically, compared with R2, R1 exhibited a higher affinity and a higher sensitivity (detection limit of 9.69 nM) toward CN− in THF- H2O (3:7, v/v) mixture.

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