Synthesis and logic gate application of quinoline schiff base probe for fluorescence detection of mercury ions

Abstract

Herein, we report the synthesis of a small molecule quinoline Schiff-base “turn-on” fluorescence probe L, denoted as (2-NC₉H₆)C(H)=N(C₆H₄OCH₃-p), utilizing 4-aminoanisole and quinoline-2-carboxaldehyde as precursors. The synthesized probe was comprehensively characterized through EA,¹H/¹³C NMR, FT-IR, and ESI-MS spectral analysis. In a CH₃CN/H₂O solution (1/1, v/v, 0.01 M PBS buffer, pH = 7.30), probe L responded to Hg(II) with high sensitivity (LOD = 2.98 × 10⁻⁷ M) and selectivity. Upon binding to Hg(II), the fluorescence of the probe shifted from being initially off to a distinct blue emission. The probe L to Hg(II) binding ratio was 1:1 and the binding constant was 1.955 × 10⁴ M⁻¹. The detection mechanism of Hg(II) by probe L is due to the complex formation between the metal ion and imine nitrogen (–CH = N), thus causing chelation-enhanced fluorescence. TD-DFT studies at the B3LYP/6-31G(d) level of theory further confirmed that the complexation of L and Hg(II) occurred. Finally, probe L could reversibly identify Hg(II) upon adding EDTA, thus developing a molecular logic gate. In addition, this probe was successfully used to detect Hg(II) in actual water samples.

 

Keywords:

• Schiff base
• fluorescence probe
• mercury ion
• DFT

Authors’ contributions

Jing-Jing Zhai: writing–original draft, methodology, investigation, data curation. Yu-Wei Dong: writing–original draft, methodology, investigation. Wei Chen: DFT studies. Xiu-Bin Bu: Measurement and analysis of single crystal X-ray diffraction data. Zhou Yu: investigation, funding acquisition.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (no. 22302131) and the Young and Middle aged Science and Technology Innovation Talents program of Shenyang (RC220317).