A Highly Selective and Sensitive Sequential Recognition Probe Zn 2+ and H 2 PO 4 - Based on Chiral Thiourea Schiff Base.

A series of novel chiral thiourea fluorescent probes HL 1 - HL 6 were designed and synthesized from (1 R ,2 R )-1,2-diphenylethylenediamine, phenyl isothiocyanate, and different substituted salicylic aldehydes. All of the compounds were confirmed by 1 H NMR, 13 C NMR, and HRMS. They exhibit high selectivity and sensitivity to Zn 2+ in the presence of nitrate ions with the detection limit of 2.3 × 10 -8 M ( HL 5 ). Meanwhile, their zinc (II) complexes ( L -ZnNO 3 ) showed continuous response to H 2 PO 4 - in acetonitrile solution. The identification processes could further be verified by supramolecular chemistry data analysis, X-ray single-crystal diffraction analysis, and theoretical study. The research provides reliable evidence for an explanation of the mechanism of action of thiourea involved in coordination, which is important for the application of thiourea fluorescent probes. In short, the sensors HL 1 - HL 6 based on chiral thiourea Schiff base will be promising detection devices for Zn 2+ and H 2 PO 4 - .