Schiff Base Constructed from 2-Thiophene Carbaldehyde and O-Phenylenediamine and its Co (Ii), Ni (Ii), and Cu (Ii) Complexes: Synthesis, Characterisation, and Antimicrobial Studies

Schiff base derived from 2-thiophene carbaldehyde and o-phenylenediamine was synthesized. The Schiff base underwent reflux with the corresponding metal (II) chlorides to produce Co(II), Ni(II), and Cu(II) complexes. These complexes were characterized through various analytical methods including FT-IR spectroscopy, determination of melting/decomposition temperatures, solubility assessments, magnetic susceptibility measurements, atomic absorption spectroscopy, conductivity analysis, and elemental analysis. In the FT-IR spectra of the Schiff base, a distinctive vibrational peak at 1622 cm-1 was observed, attributed to the azomethine υ(C=N) vibration frequencies. Interestingly, shifts in the vibrational bands (of azomethine) were noted in the complexes, indicating their involvement in complex formation. Absorption bands in the range of 713 – 769 cm-1 in the complexes were linked to M-N bond formation, confirming the presence of metal-nitrogen bonds. The complexes exhibited low molar conductance values (6–13 Ohm-1 cm2 mol-1), indicating their non-electrolytic nature. The Schiff base displayed a melting point of 120°C, whereas the complexes showed decomposition temperatures within the range of 155-196°C, signifying their thermal stability. The magnetic susceptibility values deduced suggested an octahedral geometry for all complexes, ranging between 2.24-3.12BM. Elemental analysis of the Schiff base and its metal(II) complexes for C, H, and N content revealed close agreement between observed and calculated percentages, suggesting a 1:2 metal-Schiff base ratio in all complexes. Qualitative tests confirmed the presence of chloride in the complexes, with estimated percentages falling between 4.62-7.90%. Furthermore, the synthesized Schiff base and its metal (II) complexes were evaluated for their antibacterial and antifungal activities against various microbial species.