Selective extraction of palladium(II) using hydrazone ligand: A novel fluorescent sensor

The acyclic tridentate blue luminescent ligand (λex=300 nm, λem=415 nm) quinoline-2-carboxaldehyde 2-pyridylhydrazone, HL, 1, was recognized as a new fluorescent chemosensor for Pd2+. In alkaline methanol complete fluorescent quenching was observed in the presence of 2 equivalents of Pd2+ that was further reflected in the solid phase fluorescence microscopic study. Ligand formed 1:1 complexes with Ni2+, Cu2+, Zn2+, Pd2+ and 1:2 complexes with Co2+, Fe2+ as obtained from Jobʹs plot of continuous variation. The binding constants of different metal complexes (Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Pd2+) were estimated by fluorescence titrations. The ligand can selectively extract significant amount of Pd2+ from the aqueous mixture of metal ions, and the extraction efficiency was increased from 80% to 95% with increase in the molar ratio of HL, 1, to Pd2+ from 1 to 3. No significant interference was observed up to 2-fold excess addition of Cu2+ and Zn2+ and 100-fold excess addition of Co2+, Fe2+ and Ni2+over the Pd2+ ion concentration (1.0×10−3 M).