A new "ON-OFF" fluorescent and colorimetric chemosensor based on 1,3,4-oxadiazole derivative for the detection of Cu2+ ions

A symmetrical oxadiazole derivative (OXD) containing two pyrazole moieties was synthesized successfully and characterized by single crystal X-ray diffraction, nuclear magnetic resonance and mass spectrometry. The synthesized compound displayed "On-Off" fluorescent sensing towards Cu2+ with high selectivity and sensitivity. Fluorescence and UV-vis absorbance spectra studies demonstrated that the proposed sensor can detect Cu2+ directly in acetonitrile solution over a wide range of metal ions including Ag+, Na+, K+, Hg2+, Mg2+, Cd2+, Co2+, Ni2+, Zn2+, Fe2+, Pb2+, Ca2+, Mn2+, Ba2+, Fe3+, Al3+, and Cr3+. Moreover, the synthesized sensor exhibits an instantaneous naked-eye color change from colorless to yellow with the presence of Cu e ' ion. The fluorescence intensity of the sensor has shown a linear response to Cu2+ in the concentration range of 0-15 mu M with a detection limit of 2.14 mu M. Fluorescence titration, H-1 NMR spectrum, ESI-MS, and DFT calculation confirmed that fluorescence quenching is caused by the complex formation between the sensor and Cu2+ with 1:1 stoichiometry. (C) 2018 Elsevier B.V. All rights reserved.