Quinoline-Based “On-Off” Fluorescent Sensor for Acetate: Effect of Link Mode between Binding Sites and Fluorophore on Fluorescence Changes

ABSTRACT

A novel colorimetric and fluorescence anion sensor based on 8-nitroquinolyl-2-aldehyde phenyl-thiosemicarbazone (1) was designed and synthesized according to the approach that the binding sites were covalently linked to the signaling units. In DMSO, sensor 1 exhibited a naked-eye color change from colorless to yellow upon complexation with acetate. The association constant of 1 for acetate ion was determined to be 1.20 × 10³ M⁻¹ by nonlinear fitting analyses of the titration curves. The strong interactions of compound 1 with acetate ion could be rationalized on basis of not only the guest basicity but also shape complementarity between 1 and acetate. In addition, the fluorescence emission of 1 was effectively quenched upon addition of acetate ions owing to the fact that the photoinduced electron transfer (PET) was enhanced.

KEYWORDS:

• anion sensor
• fluorescence
• “naked-eye”
• PET
• quinoline

ACKNOWLEDGMENTS

The project was supported by Nanjing Forestry University Start-up Fund (No: 163101026).

Notes

^a All the anions were added in the form of tetra-n-butylammonium (TBA) salts.

^b The association constants were determined according to by the UV-Vis spectra.

^c The association constant could not be determined.

^d The association constants were determined according to by the fluorescence spectra.