Synthesis, Characterization, and Antimicrobial Evaluation of Mn(II), Fe(II), and Co(II) Complexes of a Pyrrole-Based Thiosemicarbazone Schiff Base

A new Schiff base ligand was synthesized via the condensation of 4-methyl-3-thiosemicarbazide with 1H-pyrrole-2-carboxaldehyde and subsequently coordinated with Mn(II), Fe(II), and Co(II) ions. The ligand and its metal complexes were characterized using FT-IR, UV–Visible spectroscopy, elemental analysis, magnetic susceptibility, molar conductance, and melting/decomposition temperature determination. Infrared spectral shifts of the azomethine ν(C = N) band, together with the appearance of metal–nitrogen and metal–sulfur vibrational bands, confirm coordination through the azomethine nitrogen and thione sulfur atoms. Electronic and magnetic data support a high-spin octahedral geometry for all complexes. The complexes exhibit improved thermal stability and low molar conductance values, indicating non-electrolytic behavior. Antimicrobial evaluation against Staphylococcus aureus , Escherichia coli , Salmonella typhi, Candida albican , Tinea pedis and Aspergillus flavus revealed enhanced activity for the metal complexes relative to the free ligand, highlighting the role of chelation in modulating biological efficacy.