Turn on Fluorescence Sensing of Zn2+ Based on Fused Isoindole-Imidazole Scaffold

Abstract

Optical chemosensors caused a revolution in the field of sensing due to their high specificity, sensitivity, and fast detection features. Imidazole derivatives have offered promising features in the literature as they bear suitable donor/acceptor groups for the selective analytes in the skeleton. In this work, an isoindole-imidazole containing a Schiff base chemosensor (1-{3-[(2-Diethylamino-ethylimino)-methyl]-2-hydroxy-5-methyl-phenyl}-2H-imidazo[5,1-a]isoindole-3,5-dione) was designed and synthesized. The complete sensing phenomena have been investigated by means of UV-Vis, fluorescence, lifetime measurement, FT-IR, NMR and ESI-MS spectroscopic techniques. The optical properties of the synthesized ligand were investigated in 3:7 HEPES buffer:DMSO medium and found to be highly selective and sensitive toward Zn2+ ion through a fluorescence turn-on response with detection limit of 0.073 μm. Furthermore, this response is effective in gel form also. The competition studies reveal that the response of the probe for Zn2+ ion is unaffected by other relevant metal ions. The stoichiometric binding study was performed utilizing Job’s method which indicated a 1:1 sensor–Zn2+ ensemble. Computational calculations were performed to pinpoint the mechanism of sensing.

A Simple and Rapid Quinoline Schiff Base as a Fluorescent Probe for Zn2+ and Its Application in Test Strips

“…The corresponding plot of fluorescence intensity versus Zn 2+ concentration was constructed, and a strong linear correlation (Y=‐81.23867+1.0517E8*X, R 2 =0.99591, Figure 3b) was observed over the range of 1~10 μM. Importantly, the remarkable limit of detection (LOD) for Zn 2+ using the rule of 3σ/slope, [40–42] was calculated to be 1.04×10 −7 M compared to the previously published probes [6,26,27,43–59] (Table 1). In addition, the association constant ( K ) for L− Zn 2+ complexation was determined by Benesi‐Hildebrand equation: $${{{{F}_{max}-{F}_{min}}\over{F-{F}_{min}}}={{1}\over{K\left[M\right]}}+1}$$ , [60] to be 3.496×10 4 M −1 (Figure S10), which confirms binding affinity of L towards Zn 2+ .…”

Recent Developments in the Detection of Zn2+ Ions Using Schiff Base Probes

“…This chemosensor also detects Al 3+ ions. Sahu et al 56 synthesized a turn-on fluorescence moiety 10 (Figure 3) based on the isoindole-imidazole scaffold for the detection of Zn 2+ ions. This Schiff base chemosensor was synthesized and characterized with the help of various spectroscopic techniques such as HRMS, HMR, and FTIR spectroscopy.…”