Synthesis, characterization, and antimicrobial activity of Ni (II) and Cu (II) complexes with schiff base derived from pyrrole-2-carboxaldehyde and thiosemicarbazide

A novel Schiff base ligand was synthesized from the condensation of substituted thiosemicarbazide and 1H- 1H-pyrrole-2-carboxaldehyde. The corresponding Ni(II) and Cu(II) complexes were obtained by refluxing the chloride of the metals with the prepared Schiff base in an ethanolic solution. The Schiff base and its complexes were characterized and analyzed using Fourier Transform Infrared (FT-IR), UV-visible, magnetic susceptibility, conductivity measurement, melting point/decomposition temperature, and solubility test. The Infrared spectral data of the Schiff base showed an absorption band at 1585 cm-1, attributed to ν(C=N) stretching. However, this band was shifted to a higher frequency of 1590cm-1 and 1596cm-1 indicating the formation of a Ni-N and Cu-N band in the complexes respectively. The UV-Visible studies revealed significant red shifts in the characteristics C=N and C=S bands upon complexation confirming strong ligand-metal coordination. The complexes exhibited enhanced thermal stability (with decomposition temperatures of 217°C for Ni(II), 205°C for Cu(II) ). Magnetic measurements indicated a high-spin octahedral geometry for the Ni(II) complex (µ-eff =2.9B.M) and a distorted octahedral (Jahn-Teller) geometry for the Cu(II) complex (µ-eff =1.90B.M). The molar conductance value of the Ni(II) complex was observed at 38.20 ohm-1 cm2 mol-1 while that of the Cu(II) complex was observed at 24.20 ohm-1 cm2 mol-1 suggesting non-electrolytic nature of the complexes. The Schiff base and the complexes were screened for antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa (Bacterial strains), Candida albicans, Tinea capitis and Tinea pedis (fungal strains with Ciprofloxacin and Ketoconazole serving as control drugs for bacteria and fungi, respectively. The results demonstrated that metal complexation significantly enhances bioactivity relative to the free ligand, although their activity was lower than that of the standards.