A polynuclear CuIIBiIII complex with antipyrine‐derived Schiff‐base: Preparation, characterization, and biological evaluations

Schiff base {(E)‐4‐((2‐hydroxy‐3‐methoxybenzylidene)amino)‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one} was prepared by the condensation reaction between 2‐hydroxy‐3‐methoxybenzaldehyde and 4‐aminoantipyrine. In the process of forming the title complex, Schiff base was first coordinated with CuII ions to form the mononuclear CuII complex (abbreviated as the complex (I)). Next, Schiff base in the complex (I) removed a phenyl group and then changed from the amide to the iminol. The tautomer further formed the complex through the iminol oxygen, and the phenolic oxygen coordinated with metal ions (CuII and BiIII). The structure of the polynuclear CuIIBiIII complex (abbreviated as the complex (II)) was identified as [Bi2Cu6 L6O3] (L = C13H13N3O3) by elemental analysis, FT‐IR spectra, and single‐crystal X‐ray diffraction analysis. The antibacterial effect of Schiff base and its complex (II) were assessed on four bacterial strains involving gram‐positive strains (S. aureus and B. subtilis) and gram‐negative strains (E. coli and P. aeruginosa). The complex (II) exhibited stronger antibacterial activity than Schiff base. Assessment of cytotoxic activity against SNU‐16 cells (Human gastric cancer) has demonstrated that the complex (II) was more active than Schiff base, and their IC50 values were 0.29 and 1.83 μM, respectively. A new polynuclear CuIIBiIII complex [Bi2Cu6 L6O3] (L = C13H13N3O3) with antipyrine‐derived Schiff‐base was synthesized and structurally characterized by single crystal X‐ray diffraction. The antibacterial and cytotoxic activities of Schiff base and its complex (II) were screened to understand the effect of metal ions binding to Schiff base. The complex (II) displayed much stronger biological activities than Schiff base.