A polynuclear Cu^IIBi^III 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 Cu-II ions to form the mononuclear Cu-II 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 (Cu-II and Bi-III). The structure of the polynuclear (CuBiIII)-Bi-II 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 mu M, respectively.