With the aim of developing potential antimicrobials, a series of new 5-fluoroisatin derivatives incorporated with different secondary amines (piperidine, morpholine, pyrrolidine, dimethylamine, and diphenylamine) for monomer, and (piperazine) in case of dimer Mannich bases, separately in presence of formaldehyde to obtain Mannich bases of 5-fluoroisatin derivatives, which then each Mannich derivatives reacts with phenylhydrazine to form Schiff bases as final products. The resulting compounds were characterized by two spectroscopic analyses; (Fourier- transform infrared) FT-IR and proton nuclear magnetic resonance spectroscopy (¹H-NMR). In addition, the in vitro antibacterial and antifungal activities were tested against some human pathogenic microorganisms by employing the well-diffusion technique. The majority of these derivatives showed activity against several microorganisms. The relationship between the functional group variation and the biological activity of the evaluated compounds is discussed. From the comparison, the resulting compounds, (4b and 4d) were determined to be the most potent compounds. Dimer 6 exhibits an acceptable activity toward the bacterial stain; P. mirabilis.
