2-Chloro-5-(trifluoromethyl)aniline-Derived Schiff Base Palladium(II) Complexes: From Molecular Design to Acute Toxicity Assessment

Abstract

Four Schiff bases newly synthesized from 2-chloro-5-(trifluoromethyl)aniline served as ligands for the preparation of four palladium(II) complexes. Characterization of all compounds was performed using the following physicochemical techniques: elemental analysis, IR, UV–vis, ¹H NMR, ¹³C NMR, mass spectrometry, thermal analysis, molar conductivity, and magnetic susceptibility. In addition, crystals of the ligands HL¹–HL⁴ and the complexes 2 and 4 were obtained, enabling their structures to be confirmed by single-crystal X-ray diffraction. Crystallography showed that ligands form molecular crystals with one molecule per unit cell, except HL¹, which contains two chemically identical molecules; HL¹, HL², and HL⁴ are centrosymmetric, and HL³ crystallizes as a pure enantiomer. Complex 4 is mononuclear, coordinated by two deprotonated ligands through an N₂O₂ donor set, while complex 2 is dinuclear, with each palladium(II) coordinated via an O₃N set by one bidentate anionic ligand and two bidentate-bridging acetate anions. Phytotoxicity and animal toxicity were assessed using Triticum aestivum L. and Artemia franciscana Kellogg, respectively. Complexes were slightly more inhibitory than ligands on Triticum, but overall effects were weak, with root growth exceeding that of the negative control at all tested concentrations. Only complexes 2 and 4 exhibited dose-dependent toxicity in Artemia, with LC₅₀ values of 389.8 and 48.7 µM.