New morpholino acetamide ligand's rare earth metal complexes through synthesis, structural, and theoretical studies. Effect of ligand on aluminum alloy corrosion inhibition

Abstract

A series of new complexes of the general formula [Ln(L)Cl2]Cly·4H2O (Ln = Er and Ta) and [Yb(L)(H2O)2]Cl3, L = N,N'-((ethane-1,2-diylbis(sulfanediyl))bis(2,1-phenylene))bis-(2-morpholino-acetamide) were synthesized and characterized. The physical properties of these complexes were investigated including melting point, color, and percentage yield. Spectral and physico-analytical techniques collectively with elemental analyses were utilized to structurally elucidate the synthesized complexes. At room temperature, complexes exhibited similar solution absorption spectra in the UV–Vis region. As shown by thermal analysis, the complexes lose water molecules first, then anions, and finally ligand molecule, leaving a metal oxide residue. The complexes resulted from monomolar coordination of neutral tetradentate ligand through the two amide nitrogen and the two sulfur, with octahedral geometries. Ligand and its Ta(V) complex were structurally characterized by X-ray powder diffraction. Their optical band gaps demonstrated the ligand and complexes have semiconducting properties. Multiple bonding patterns were discovered in molecular docking simulations of the ligand against SARS-CoV-2 (6Y84) and E. coli DNA gyrase (5MMN). The binding energy of the complexes revealed active compounds capable of inhibiting SARS-CoV-2 and E. coli DNA gyrase. The antioxidant activity of the ligand and its Ln-complexes was investigated, yielding some surprising results. Finally, it is worthy to note that, the biochemical outcomes revealed that these complexes may be promising antibacterial agents. Aluminum alloys (AlSi) corrosion inhibition was investigated in 1 M HCl using potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The inhibition efficiency was found to be 96.36 % at 500 ppm inhibitor in 1 M HCl.