Pd(II) Complexes of Schiff Base Ligands Derived From 4‐Aminoantipyrine: Synthesis, Characterization, Crystal Structure and Acute Toxicity Evaluation

A series of palladium(II) complexes, [Pd(L 1 ) 2 ] ( 1 ), [Pd(L 2 ) 2 ]·2DMSO ( 2 ), [Pd(L 3 ) 2 ] ( 3 ), [Pd(L 4 )(CH 3 COO) 2 ] ( 4 ), [Pd(L 5 ) 2 ]·1.25H 2 O ( 5 ), and [Pd(L 6 ) 2 ] ( 6 ) with Schiff bases derived from 4‐aminoantipyrine, HL 1 – HL 6 , have been synthesized. The newly obtained ligands and corresponding complexes have been described using the following physicochemical methods: 1 H‐NMR, 13 C‐NMR, UV–vis, IR spectroscopies, elemental analysis, magnetic susceptibility, molar conductivity, and thermal analysis. Additionally, the molecular structures of ligands HL 1 , HL 3 , and HL 6 and complexes 1 , 2 , 3, and 6 were confirmed by single‐crystal X‐ray diffraction. All crystal structures were found to be centrosymmetric, with no interstitial solvent molecules, except for [Pd(L 2 ) 2 ]·2DMSO, which crystallized as a disolvate from DMSO. Furthermore, this analysis showed that each palladium(II) is coordinated by a set of four N 2 O 2 donor atoms, adopting a square‐planar geometry. The acute toxicity of all compounds was assessed on two species: the monocot Triticum aestivum L. and the aquatic crustacean Artemia franciscana Kellogg. The results from macroscopic and microscopic plant evaluations confirmed the absence of a phytotoxic effect for the ligands and indicated a weak effect for complexes 2 ‐ 6 . In addition, most of the tested compounds did not induce mortality in crustacean nauplii at concentrations up to 100 µM.