A highly selective chemosensor for nickel(II) based on fluorescence quenching of a bispyrazole derivative

A novel bispyrazole, 2,6-bis(5-phenyl-1H-pyrazol-3-yl)-pyridine, was designed and synthesized. The bispyrazole showed extreme selectivity for Ni2+ over other metal ions such as Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Hg2+, K+, Mg2+, Na+, Pb2+, and Zn2+ in MeOH–H2O solution. The sensing sensitivity and binding properties of the bispyrazole for nickel(II) ion were investigated by fluorescent spectroscopic techniques. It was found that the bispyrazole possessed high selectivity and sensitivity toward Ni2+ over other metal ions. The binding stoichiometry was confirmed as 1:1 (bispyrazole/Ni2+) by Job plot experiment and the linearity of the Benesi–Hildebrand plot. The binding constants K and thermodynamic parameters (ΔH, ΔG, and ΔS) at different temperatures were obtained. Meanwhile, the detection limit of the bispyrazole for Ni2+ was determined to be 3.25 × 10−7 mol L−1.