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Styrylpyridinium dye bearing azadithia‐15‐crown‐5 ether receptor group SP and 4‐alkoxy‐1,8‐naphthalimide fluorophore were linked using copper‐catalyzed azide‐alkyne cycloaddition click reaction to afford dyad compound NI‐SP. Chemosensor NI‐SP exhibited selective ratiometric fluorescent response to the presence of Hg2+ in aqueous solution due to the interplay between resonance energy transfer (RET) and intramolecular charge transfer (ICT) processes occurred upon excitation. The observed switching of the ratio of emission intensities in the blue and red channels R was higher than in the case of monochromophoric styrylpyridine derivative SP showing ratiometric response based on ICT mechanism only. Biological studies revealed that NI‐SP penetrates into human lung adenocarcinoma A549 cells and accumulates in cytoplasm and lysosomes. When cells were pre‐incubated with mercury (II) perchlorate, the ratio R was increased 2.6 times, which enables detection of intracellular Hg2+ ions and their quantitative analysis in the 0.7–6.0 μM concentration range. [ABSTRACT FROM AUTHOR]

[Display omitted] A novel derivative of 4-styryl-1,8-naphthalimide containing an N -arylazadithia-15-crown-5-ether moiety as a receptor exhibited a hypsochromic shift with simultaneous fluorescence quenching upon complexation with the mercury(II) cation. The compound is suggested as a selective fluorescent chemosensor for the detection of Hg2+ in aqueous solutions and in HEK 293 cells. [ABSTRACT FROM AUTHOR]

Bis(styryl) dye 1 bearing N-phenylazadithia-15-crown-5 ether receptor has been evaluated as a ratiometric fluorescent chemosensor for mercury (II) ions in living cells. In aqueous solution, probe 1 selectively responds to the presence of Hg2+ via the changes in the emission intensity as well as in the emission band shape, which is a result of formation of the complex with 1:1 metal to ligand ratio (dissociation constant 0.56 ± 0.15 µM). The sensing mechanism is based on the interplay between the RET (resonance energy transfer) and ICT (intramolecular charge transfer) interactions occurring upon the UV/Vis (380 or 405 nm) photoexcitation of both styryl chromophores in probe 1. Bio-imaging studies revealed that the yellow (500–600 nm) to red (600–730 nm) fluorescence intensity ratio decreased from 4.4 ± 0.2 to 1.43 ± 0.10 when cells were exposed to increasing concentration of mercury (II) ions enabling ratiometric quantification of intracellular Hg2+ concentration in the 37 nM–1 μM range. [ABSTRACT FROM AUTHOR]