Synthesis, characterization, and biological potential of 2-thiophene carbaldehyde o-phenylenediamine Schiff base and its Cr(II), Mn(II), and Fe(II) Complexes

Abstract

A Schiff base was produced through the chemical reaction of 2-thiophene carbaldehyde with o-phenylenediamine. The corresponding metal (II) chlorides were refluxed with the Schiff base to produce the complexes of Cr (II), Mn (II), and Fe (II). These complexes were then characterized by elemental analysis, FT-IR, atomic absorption spectroscopy, solubility, melting/decomposition temperature, and magnetic susceptibility. The vibrational peak at 1622 cm̄1 in the FT-IR spectral data of the Schiff base was ascribed to the vibration frequencies of azomethine u(C=N). But in the complexes, it was discovered that the azomethine band shifted between 1614 and 1659 cm̄1 , suggesting that they were involved in the complexes’ creation. The complexes’ measured absorption bands in the range of 713–769 cm1 were attributed to the M–N bond, indicating the occurrence of metal–nitrogen bonds. The complexes exhibit non-electrolyte properties attributed to their low molar conductance values ranging from 8.00 to 29 Ohm̄1 cm̄ ²mol̄¹. The determination of the melting point of the Schiff base yielded 120 °C, while the decomposition temperature fell within the range of 149–160 °C for the complexes, indicating their thermal stability. Analysis of magnetic susceptibility indicated an octahedral geometry for all the complexes, with values ranging from 2.24 to 3.12 BM. The elemental should analysis of both the Schiff base and its metal (II) complexes for C, H, and N indicated a close agreement between observed and calculated percentages, suggesting a consistent 1:2 metal-Schiff base ratio across all complexes. The qualitative analysis of the compounds confirmed the presence of chloride, which was quantified and determined to range from 4.62% to 7.90%. The prepared Schiff base and its metal (II) complexes underwent evaluation for their antibacterial efficacy against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa, as well as their antifungal properties against Candida albicans and Aspergillus niger. The results of the experiments indicated that the metal complexes displayed notable antimicrobial effects.