Synthesis and structural characterization of new 2-bromo-1,3-bis(triazol-1- ylmethyl)benzene ligands. Study of their behavior as complexing agents for determination of nickel(II) by adsorptive stripping voltammetry

Reaction of 2-bromo-1,3-bis(bromomethyl)benzene (1) with 1,2,3-triazole and benzotriazole yields 2-bromo-1,3-bis(triazol-1-ylmethyl)benzene (2) and 2-bromo-1,3-bis(benzotriazol-1-ylmethyl)benzene (3), isolated as white solids, air stable at room temperature, and characterized by elemental analysis, mass spectra, IR, and NMR (¹H, ¹³C) spectroscopy. The molecular structure of 3 was determined by single-crystal X-ray diffraction. These ligands were evaluated for determination of ultra-trace concentrations of nickel by adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the Ni(II)-L complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using square wave modulation. However, only with 2 was a signal observed at -0.81 V. Under the best experimental conditions (pH 5.5; ligand concentration 0.30 μmol L^-1; adsorptive potential (E_ads) -0.70 V and adsorptive time (t_ads) 80 s), the peak current is proportional to the Ni(II) concentration to 15.0 μg L^-1, with a 3 detection limit of 0.2 μg L^-1. The proposed method was validated by determining Ni(II) in certified reference waste water (SPS-WW1) with satisfactory results.