Imine-functionalized thioether Zn(ii) turn-on fluorescent sensor and its selective sequential logic operations with H2PO4−, DFT computation and live cell imaging

Abstract

The diformyl thioether Schiff base (H₂L) exhibits fluorescent sensing behaviour towards Zn²⁺ with a limit of detection (LOD) of 0.050 μM, which is far below the WHO guideline (76 μM) in drinking water. The formation of a 1 : 1 metal-to-ligand complex, [ZnL], has been ascertained by X-ray crystallography, Job's plot and mass spectra. The fluorogenic complex, [ZnL] (either in situ or a solution of the isolated complex) has shown selective ON–OFF emission toward H₂PO₄⁻. A two-input, one-output sequential INHIBIT logic circuit has been constructed from H₂L, Zn²⁺ and H₂PO₄⁻. The practical applicability of H₂L has been examined by the identification of Zn²⁺ and H₂PO₄⁻ in the intracellular fluid of African monkey Vero cells.