Naphthalene-based turn-on fluorescent probe for sensitively recognizing Zn²⁺

Abstract

A Schiff-base type fluorescent sensor (PLB3) was synthesized by nucleophilic addition-elimination between 2-hydroxy-1-naphthaldehyde and 5-chloro-2-aminopyridine. Single crystal X-ray diffraction analysis demonstrated keto-amine isomer was predominantly adopted. 8-Fold fluorescence-enhanced recognition for detecting Zn²⁺ was chelation enhanced fluoresce (CHEF) mechanism. Also, PLB3 could distinguish well Zn²⁺ from analogue Cd²⁺. Job’s plot fluorescence titration and UV–Vis titration revealed the 1:1 stoichiometry between Zn²⁺ and PLB3. The association constant (K_a) and limit of detection (LOD) were 5.14 × 10⁷ M⁻¹ and 0.33 μM, respectively. The excellent selective and sensitive properties urge PLB3 to detect the trace amounts of Zn²⁺ in the environmental systems.

Keywords:

• Chelation enhanced fluoresce
• keto-amine isomer
• naphthalene
• pyridine
• zinc ion

Supplementary material

Crystallographic data have been deposited with the Cambridge Crystallographic Data Center as supplementary publication, No. CCDC 2124608 for PLB3. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Telephone: [phone]; Fax: [phone]; email: [email protected]). These data can be also obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html. And the detailed materials about apparatus, NMR spectra, MS spectra, IR and so on were listed in supporting information.

Additional information

Funding

The authors would like to express the wholehearted thanks to the financial support for the following funds and organizations: National Natural Science Foundation of China (62064006), Natural Science Foundation of Gansu Province (20JR5RA403), Innovation Fund Project of Colleges and Universities in Gansu (2020A-042), Lanzhou Jiaotong University (LZJTU) - Tianjin University Joint Innovation Fund (2019056).