Synthesis, characterization, antibacterial, antioxidant activities, density functional theory, and molecular docking studies of new organic metal complexes and links to application of corrosion inhibitors

Abstract

The condensation reaction between 5‐amino‐1,3,4‐thiadiazole‐2‐thiol and 1,2‐dibromoethane to afford the ligand L was carried out in direct to obtain the desired organic ligand. New [Er(L)ClH2O]Cl2·3H2O, [Yb(L)(H2O)2]Cl3·4H2O, and [Ta(L)Cl2]Cl3·4H2O complexes have been prepared from (L) by reacting one mole from metal ions with one mole from L. In addition to their physical characteristics, they were described using spectroscopic techniques (infrared [IR], nuclear magnetic resonance [NMR], and UV–Vis), gas chromatography (GC)‐mass, and X‐ray powder diffraction. Further interpretation of complex structures was supported by measurements of molar conductivity, magnetic susceptibility, mole ratio, and thermodynamic investigations in addition to theoretical study through the use of density functional theory and characterization techniques. IR spectral data showed the mode of action of the neutral tetradentate L ligand and its coordination via two N‐amine and two S‐thiols. The octahedral geometry surrounding the central lanthanide ions was suggested by the magnetic moments, diffused reflectance, and spectral data. Molar conductivity results exposed that Yb(III) and Ta(V) chelates were 1:3 electrolytes and Er(III) chelate was 1:2 electrolyte. In addition, practically all the complexes demonstrated effective antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus species, via inhibition zone diameters in 9–15 mm mg−1 range. However, neither Candida albicans nor Aspergillus flavus species were susceptible to their antifungal effects. Finally, molecular docking (MOE) experiments showed the significant binding affinity of the ligand and its complexes with several 6KOC, 6LU4, and 6LU4 protein receptors. Finally, it is important to emphasize that these complexes may be potential antioxidant agents according to the biochemical results. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) methods were accustomed to examine the corrosion inhibition of aluminum silicon alloys (AlSi) in 1 M HCl solution. Experimental measurements indicate that the thiadiazole ligand reduces the corrosion rate.