Synthesis, spectral characterization and investigation of biological properties of Cu(II) Schiff base complex derived from 4-aminoantipyrine

As early as 1884, Knorr discovered the antipyretic (temperature reducing) action of a pyrazole derivative in humans, and due to its antipyretic property he named the compound Antipyrine. Transition metal complexes of pyrazolone derivatives are of great interest due to their biological activities, especially pyrazolone Schiff-base derivatives. Schiff base of 4- aminoantipyrine and its complexes have a variety of applications in biological, clinical and pharmacological areas [1–3]. In this research, we report the synthesis of Cu(II) complex containing Schiff base derived from 4-aminoantipyrine and 5-hydroxysalicylaldehyde. The Schiff base ligand was prepared using reaction of 5-hydroxysalicylaldehyde with 4- aminoantipyrine in ethanol at room temperature. This ligand was characterized by 1H-NMR, 13C-NMR, FT-IR and single crystal X-ray diffraction. Complex was prepared by direct reaction between the Schiff base ligand and the corresponding metal salt. The metal center possesses a distorted square planar geometry with N2O2 donor atoms coordinating from Schiff base ligand. Even though the ligand is tridentate in nature, it binds the Cu(II) ion, in a bidentate fashion through the deprotonated phenolic oxygen of the phenyl ring and nitrogen of the azomethine group, leaving the antipyrine exocyclic ketonic oxygens free. The steric strain imposed by the methyl substitution on the antipyrine moiety restricts the ligand towards bidentate coordination from its tridentate nature. The in vitro biological screening effects of the synthesized compounds were tested against different microbial kinds via MIC test. Our results revealed the more antimicrobial activity of the ligand than their Cu(II) complexe