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

Abstract

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.