Synthesis, characterization, and thermal and antimicrobial studies of newly developed transition metal-polychelates derived from polymeric Schiff base

Monomeric Schiff base derived from salicylaldehyde and 1,3-diaminopropane was subjected to polycondensation reaction with formaldehyde and piperazine in basic medium. The resin was found to form polychelates readily with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) metal ions. The materials were characterized by elemental analysis, spectral studies (IR, ¹H-NMR, ¹³C-NMR, and UV-visible), magnetic moment measurements, and thermal analysis. The electronic spectra and magnetic moment measurements of the synthesized polychelates confirmed the geometry of the central metal ion. Metal-resin bonds were registered in the IR spectra of the polychelates. The thermogravimetric analysis data indicated that the polychelates were more stable than the corresponding polymeric Schiff base. All the synthesized metal-polychelates showed excellent antibacterial activities against the selected bacteria. The antimicrobial activities were determined by using the shaking flask method, where 25 mg/mL concentrations of each compound were tested against 10⁵ CFU/mL bacteria solutions. The number of viable bacteria was calculated by using the spread-plate method, where 100 μL of the incubated antimicrobial agent in bacteria solutions were spread on agar plates, and the number of bacteria was counted after 24 h of incubation period at 37°C.