Synthesis and performance of four Zn²⁺ fluorescent probes based on Schiff bases

Four fluorescent probes for zinc ion based on Schiff bases were synthesized from ethylenediamine and salicylaldehyde derivatives and their structures were characterized by H-1 NMR, C-13 NMR, and IR. The spectral analysis results show that probe L2 has better selectivity and sensitivity to Zn2+ than other probes and the detection limit of probe L2 was 92.15 nmol center dot L-1. There was a good linear relationship between the fluorescence intensity of probe L2 and the concentration of Zn2+ in a range of 0 to 10 mu mol center dot L-1. The visible fluorescence color change was observed with the naked eye under the ultraviolet lamp. The recognition mechanism was studied by Job's plot, NMR titration experiment, density functional theory calculation, and the crystal structure of the L2 - Zn2+ complex. The results showed that probe L2 was complexed with Zn2+ in a molar ratio of 1:1. In addition, probe L2 could detect Zn2+ in actual water samples. CCDC: 2247372, L2-Zn2+.