Synthesis, Characterization, and Antibacterial Activity Studies of two Co(II) Complexes with 2-[(E)-(3-acetyl-4-hydroxyphenyl)diazenyl]-4-(2-hydroxyphenyl)thiophene-3-carboxylic acid as a Ligand

Two new Cobalt(II) complexes 5 and 6 with 2-[( E )-(3-acetyl-4-hydroxyphenyl)diazenyl]-4-(2-hydroxyphenyl)thiophene-3-carboxylic acid 4 as a novel ligand have been synthesized. These three new compounds were characterized on the basis of their powder X-Ray Diffraction, UV-Vis, IR, NMR, elemental analysis and MS spectral data. DFT/B3LYP mode of calculations were carried out to determine some theorical parameters of the molecular structure of the ligand. The purity of the ligand and the metal complexes were ascertained by TLC and melting points. The analysis of the IR spectra of the polyfunctionalized azo compound 4 and its metal complexes 5 and 6 , reveals that the coordination patterns of the ligand are hexadentate and tetradentate respectively. Based on the UV-Vis electronic spectral data, octahedral and square-planar geometries were respectively assigned to the cobalt(II) complexes. The ligand 4 displayed moderate antibacterial activity (MIC = 32–128 µg/mL) against Staphylococcus aureus ATCC25923, Escherichia coli ATCC25922, Pseudomonas aeruginosa and Klebsiella pneumoniae 22. The octahedral Cobalt(II) complex 5 showeds moderate activity against Pseudomonas aeruginosa (MIC = 128 µg/mL) and Klebsiella pneumoniae 22 (MIC = 64 µg/mL) and none against Staphylococcus aureus ATCC25923 and Escherichia coli ATCC25922, whereas the square-planar complex 6 displayed moderate activity only on Klebsiella pneumoniae 22 (MIC = 64 µg/mL).