A reactive primary fluorescence switch-on sensor for Hg2+ and the generated fluorophore as secondary recognition receptor toward Cu2+ in aqueous acetonitrile solution

- A bi-functional probe for sequential recognition of Mercury and Copper was synthesized and characterized.
- A combination of the chemodosimeter and chemosensor approach.
- Live Cell Imaging.

A new N-methylbenzoimidazole-based fluorescence “turn-on” chemodosimeter (VPBA) was synthesized and characterized for cation to cation relay recognition (CCRR) with high sequence specificity (Hg2+ → Cu2+). The selectivity and sensitivity of VPBA have been explored in aqueous acetonitrile solution through a specific cyclization reaction triggered by the mercury-promoted hydrolysis of the vinylether group with a significant change of fluorescence color. The probe displayed a fast switch-on fluorescence response with 164 fold toward Hg2+in aquoues acetonitrile solution. Further, the in situ system generated from the sensing of Hg2+ showed good relay recognition ability for Cu2+ via fast fluorescence quenching by the formation of a 1:2 complex in aquoues acetonitrile. The complexation of Cu2+ by VPBA has been addressed by HR-MS, 1H NMR, and UV−vis spectra. The probe and their Cu-complex structures have been established by DFT calculations. TDDFT calculations were also performed in order to demonstrate the electronic properties of probe and their copper complex. By using the new strategy, the novel probe could be used for the detection of Hg2+ in real-life water samples with good recovery. The probe could be successfully used for the fluorescence image of Hg2+ in living cells. These results suggested that the probe has promising applications for Hg2+ sensing in biological and environmental sciences.

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