Synthesis, crystallography, and conducting properties of a new nickel(II) complex containing 4-(diphenylamino)benzaldehyde-4-(ethyl)thiosemicarbazone

A new Nickel(II) complex, NiL 2 , was prepared in this study by reacting 4-(diphenylamino)benzaldehyde-4-(ethyl)thiosemicarbazone and nickel(II) acetate. The resulting NiL 2 complex was thoroughly characterized by a variety of methods, such as elemental analysis, fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, magnetic susceptibility, and molar conductivity measurements. The material was also analyzed using a single-crystal X-ray diffraction (SCXRD) to identify its structural characteristics. FTIR confirmed that the ligand was bound to Ni(II) in a mononegative bidentate fashion through the azomethine (N=C) and thione sulfur (C=S) donor atoms. The UV-Vis spectrum and the measured magnetic moment are consistent with a diamagnetic species (μ eff ≈ 0 BM), indicating a square planar geometry, which was confirmed by X-ray crystallographic data. The structural analysis showed a distorted square planar geometry with bond angle deviations up to 6°. The complex crystallized in the triclinic P-1 space group and adopted the thione tautomeric form. Moreover, NiL 2 was used as a dopant in solid biopolymer electrolyte (SBE) films prepared by the solution-casting technique using carboxymethyl cellulose (CMC) as the polymer host, polyethylene glycol (PEG) as a plasticizing agent, and isophthalic acid (IA) as the protonator. The highest ionic conductivity of 4.60 × 10 -7 S cm -1 at 353 K was achieved with CMC (1 g) + PEG (0.1 mL) + NiL 2 (15 wt%) + IA (20 wt%) of the SBE composition. In addition, the conductivity follows the Arrhenius behavior with an activation energy (E a ) of 0.144 eV, indicating that it requires low thermal energy to activate the charge carrier.