A novel 2,6-diformyl-4-methylphenol based chemosensor for Zn(ii) ions by ratiometric displacement of Cd(ii) ions and its application for cell imaging on human melanoma cancer cells

Abstract

A new chelating ligand [4-methyl-2,6-bis-(pyridin-2-yl-hydrazonomethyl)-phenol] (1) was prepared by the condensation of 2-hydrazinylpyridine with 2,6-diformyl-p-cresol. Compound 1 exhibits weak fluorescence due to intramolecular photoinduced electron transfer (PET). The sensor (1) demonstrates Zn(2+)-specific emission enhancement due to the “PET off” process through a 1:1 binding mode with the metal ion. The fluorescence quantum yield of chemosensor 1 is only 0.020, and it increases more than 14-fold (0.280) in the presence of one equivalent of the zinc ion. Interestingly, the introduction of other metal ions causes the fluorescence intensity to remain either unchanged or weakened except for Cd(2+). The new sensor showed ‘naked-eye’ detection of Zn(2+) ions: a color change of the solution from colorless to yellow. Ratiometric displacement of Cd(2+) ions from the complex by Zn(2+) ions supports the formation of a more stable sensor–Zn(2+) complex over the sensor–Cd(2+) complex. The experimental findings have been correlated with theoretical results using the B3LYP functional and 6-31G (d, p), LANL2DZ basis set for Cd(2+) (2) and Zn(2+) (3) complexes, respectively, by the Density Functional Theory (DFT) method. Moreover, the ability of probe 1 to sense Zn(2+) within human melanoma cancer cells has been explored, and the Zn(2+)-probing process in living cells was found to be reversible with zinc chelator solution of N,N,N,N-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) or EDTA.

A novel polynorbornene-based chemosensor for the fluorescence sensing of Zn2+ and Cd2+ and subsequent detection of pyrophosphate in aqueous solutions

“…[1][2][3][4][5][6] Among various metal ions, fluorescent chemosensors for zinc and cadmium ions have received wide attention in the past few decades due to the indispensable role of zinc ions and the deleterious role of the cadmium to life. [7][8][9][10][11][12][13][14][15][16][17][18] Zinc is the second most abundant transition metal ion in a mammalian body, and it plays a critical role in biological processes including gene expression, apoptosis, and neurotransmission. In contrast, cadmium ion is known as an extremely toxic and potentially carcinogenic metal, and it could cause severe diseases such as renal dysfunction, calcium metabolism disorders, and certain types of cancers.…”

A novel Benzimidazole moiety-appended Schiff base derivative: Synthesis, characterization and the investigation of photophysical and chemosensor properties

“…In case of adding Zn 2+ solution to the Schiff base derivative (3), a decrease was observed in the band at 324 nm while an increment was observed at 262 and 374 nm absorbance. Besides, the observed band at 324 nm which is associated with the free ligand (3) shifted to 374 nm after mixing with the solution of the Zn 2+ and this shifting is indicative for the coordination of Zn 2+ to the 3 upon complexation (32). , the observed fluorescence emission at about 450 nm were plotted by exciting from two different wavelengths as 324 nm (Figure 6) and 378 nm (Figure 7).…”

A Phenanthroimidazole‐based Fluorescent Turn‐Off Chemosensor for the Selective Detection of Cu2+ in Aqueous Media

“…[1][2][3][4][5] Especially, fluorescent methods have been regarded as effective tools over other optical chemosensors because of their low cost, accurate analysis and high selectivity. [10][11][12][13][14][15][16] Copper, as one of the most abundant metals in the earth, is not only an essential trace metal ion for many enzymatic processes but also a pollutant because of its wide usage in modern life. [10][11][12][13][14][15][16] Copper, as one of the most abundant metals in the earth, is not only an essential trace metal ion for many enzymatic processes but also a pollutant because of its wide usage in modern life.…”

“…Especially, fluorescent methods have been regarded as effective tools over other optical chemosensors because of their low cost, accurate analysis and high selectivity . In this regard, much effort was paid to design of fluorescent chemosensors targeted at a specific transition metal ion . Copper, as one of the most abundant metals in the earth, is not only an essential trace metal ion for many enzymatic processes but also a pollutant because of its wide usage in modern life .…”