Syntheses, Characterization, and Antibacterial Activities of Four New Schiff Base Compounds Derived from 1-Phenyl-3-methyl-4-benzoyl-2-pyrazolin-5-one

Four new Schiff bases were designed and synthesized. 5-Methyl-4-(4-aminophenylamino-phenyl-methylene)-2-phenyl-2,4-dihydro-pyrazol-3-one (compound 1) and 5-methyl-4-(2-aminophenylamino-phenyl-methylene)-2-phenyl-2,4-dihydro-pyrazol-3-one (compound 2) were synthesized by interaction of 1-phenyl-3-methyl-4-benzoyl-2-pyrazolin-5-one (PMBP) with o- and p-phenylenediamine, respectively; 4,4'-(1,2-phenylenebis(azanediyl)bis(phenylmethanylylidene))bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one) (compound 3) and 5-methyl-4-(phenyl(2-((3-phenylallylidene)amino)phenylamino)methylene)-2-phenyl-2,4-dihydro-pyrazol-3-one (compound 4) were synthesized by interaction of compound 2 with PMBP and cinnamaldehyde in an ethanolic medium, respectively. The molecular structures of the title compounds were first characterized by single-crystal X-ray diffraction, mass spectrometry, and elemental analysis. The title compounds were tested for antibacterial activity (Escherichia coli, Staphylococcus aureus, and Bacillus subtilis) by disk diffusion method.