A highly selective turn-on fluorescent chemosensor for detecting zinc ions in living cells using symmetrical pyrene system

• Pyrene-malonohydrazide derivative was synthesized in two steps with high yield. • PYMH was used as high selective, sensitive and turn-on sensor for Zn 2+ . • The Zn 2+ limit of detection was found to be 5.1 nM. • The mechanism was supported by DFT/TDDFT calculations. • The probe is also capable of detecting intracellular Zn 2+ in HeLa cells. This manuscript presents a very simple receptor based on the combination of pyrene and malonohydrazide groups for the sensitive and selective detection of Zn 2+ . The sensor PYMH {N1’,N3’-bis(pyren-1-yl)ethylene)malonohydrazide} was synthesized in two simple steps involving synthesis of malonohydrazide followed by the synthesis of symmetrical pyrene malonohydrazide with two pyrene units on either side of the molecule. The synthesized PYMH was confirmed by FT-IR, 1 H NMR, 13 C NMR and Mass spectroanalytical techniques. The sensor was able to exhibit ‘turn-on’ fluorescence in the presence of Zn 2+ with no significant response from other relevant ions including Na + , K + , Ca 2+ , Mg 2+ , Cd 2+ , Cu 2+ , Co 2+ , Ni 2+ , Mn 2+ , Hg 2+ , Pb 2+ , Fe 2+ , Al 3+ , Fe 3+ and Cr 3+ . Moreover, the sensor was capable of selectively detecting Zn 2+ in the presence of its most common interferent Cd 2+ . The mechanism of fluorescent enhancement was proposed based on DFT calculations and it was established to be photoinduced electron transfer (PET). 1 H NMR titrations revealed that the Zn 2+ binding sites to be imine NH group, besides FT-IR spectra confirmed the coordination of C = O with Zn 2+ . The sensor PYMH showed the LOD of 5.1 nM (3σ/S), which is well below the permitted drinking water level of 76 μM as recommended by WHO. Further, the probe PYMH is capable of detecting distribution of intracellular Zn 2+ in HeLa cells.