Synthesis, crystal structure, and characterization of two Cu(II) and Ni(II) complexes of a tetradentate N2O2 Schiff base ligand and their application in fabrication of a hydrazine electrochemical sensor

Abstract

Two new Cu(II) and Ni(II) complexes of a tetradentate N2O2 Schiff base ligand (H2L = N,N'-bis-(4-hydroxysalicylidene)-ethylenediamine) were synthesized. The structures of the H2L ligand and its complexes (1 and 2) were unambiguously determined by elemental analysis, FT-IR, 1H NMR, and UV–Vis spectroscopy. The crystal structures of the complexes were also determined by X-ray crystallography technique. In addition, the complexes were tested as a modifier for a glassy carbon electrode (GCE) to prepare an electrochemical sensor for detection of hydrazine in real samples. The prepared sensor with Ni(II) complex showed admirable sensitivity and selectivity for determination of hydrazine at 0.55 V without any interference of other common substrates. A dynamic linear range of 0.5–150 µM with a detection limit (LOD) of 166.66 nM and sensitivity of 0.1174 μA µM−1 cm−2 was achieved. The obtained LOD was much lower than that specified in the U.S. Environmental Protection Agency (EPA) regulations. The prepared sensor was also successfully applied to detect hydrazine in Tehran’s Jajrood river water as a real sample.